2019-05-19 13:08:20 +01:00
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2015-11-06 16:30:29 -08:00
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2018-12-04 23:23:11 +02:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:59:06 -08:00
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2016-01-15 16:59:09 -08:00
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2015-11-06 16:30:29 -08:00
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mm, printk: introduce new format string for flags
In mm we use several kinds of flags bitfields that are sometimes printed
for debugging purposes, or exported to userspace via sysfs. To make
them easier to interpret independently on kernel version and config, we
want to dump also the symbolic flag names. So far this has been done
with repeated calls to pr_cont(), which is unreliable on SMP, and not
usable for e.g. sysfs export.
To get a more reliable and universal solution, this patch extends
printk() format string for pointers to handle the page flags (%pGp),
gfp_flags (%pGg) and vma flags (%pGv). Existing users of
dump_flag_names() are converted and simplified.
It would be possible to pass flags by value instead of pointer, but the
%p format string for pointers already has extensions for various kernel
structures, so it's a good fit, and the extra indirection in a
non-critical path is negligible.
[linux@rasmusvillemoes.dk: lots of good implementation suggestions]
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-15 14:55:56 -07:00
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2019-10-03 15:32:19 +03:00
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2019-04-05 12:58:57 +11:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:53 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:53 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:53 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:53 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:53 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:53 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:50 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:59:02 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:59 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:56 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:56 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:56 -08:00
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2015-11-06 16:30:29 -08:00
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2017-11-01 15:32:23 +11:00
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2018-02-16 23:07:03 +02:00
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2017-11-01 15:32:23 +11:00
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2018-06-13 19:18:40 +02:00
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2017-11-01 15:32:23 +11:00
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vsprintf: don't obfuscate NULL and error pointers
I don't see what security concern is addressed by obfuscating NULL
and IS_ERR() error pointers, printed with %p/%pK. Given the number
of sites where %p is used (over 10000) and the fact that NULL pointers
aren't uncommon, it probably wouldn't take long for an attacker to
find the hash that corresponds to 0. Although harder, the same goes
for most common error values, such as -1, -2, -11, -14, etc.
The NULL part actually fixes a regression: NULL pointers weren't
obfuscated until commit 3e5903eb9cff ("vsprintf: Prevent crash when
dereferencing invalid pointers") which went into 5.2. I'm tacking
the IS_ERR() part on here because error pointers won't leak kernel
addresses and printing them as pointers shouldn't be any different
from e.g. %d with PTR_ERR_OR_ZERO(). Obfuscating them just makes
debugging based on existing pr_debug and friends excruciating.
Note that the "always print 0's for %pK when kptr_restrict == 2"
behaviour which goes way back is left as is.
Example output with the patch applied:
ptr error-ptr NULL
%p: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%pK, kptr = 0: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%px: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 1: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 2: 0000000000000000 0000000000000000 0000000000000000
Fixes: 3e5903eb9cff ("vsprintf: Prevent crash when dereferencing invalid pointers")
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-19 13:26:57 +02:00
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2017-11-01 15:32:23 +11:00
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2018-06-13 19:18:40 +02:00
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2017-11-01 15:32:23 +11:00
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2018-06-13 19:18:40 +02:00
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vsprintf: Prevent crash when dereferencing invalid pointers
We already prevent crash when dereferencing some obviously broken
pointers. But the handling is not consistent. Sometimes we print "(null)"
only for pure NULL pointer, sometimes for pointers in the first
page and sometimes also for pointers in the last page (error codes).
Note that printk() call this code under logbuf_lock. Any recursive
printks are redirected to the printk_safe implementation and the messages
are stored into per-CPU buffers. These buffers might be eventually flushed
in printk_safe_flush_on_panic() but it is not guaranteed.
This patch adds a check using probe_kernel_read(). It is not a full-proof
test. But it should help to see the error message in 99% situations where
the kernel would silently crash otherwise.
Also it makes the error handling unified for "%s" and the many %p*
specifiers that need to read the data from a given address. We print:
+ (null) when accessing data on pure pure NULL address
+ (efault) when accessing data on an invalid address
It does not affect the %p* specifiers that just print the given address
in some form, namely %pF, %pf, %pS, %ps, %pB, %pK, %px, and plain %p.
Note that we print (efault) from security reasons. In fact, the real
address can be seen only by %px or eventually %pK.
Link: http://lkml.kernel.org/r/20190417115350.20479-9-pmladek@suse.com
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Tobin C . Harding" <me@tobin.cc>
Cc: Joe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
2019-04-17 13:53:48 +02:00
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vsprintf: don't obfuscate NULL and error pointers
I don't see what security concern is addressed by obfuscating NULL
and IS_ERR() error pointers, printed with %p/%pK. Given the number
of sites where %p is used (over 10000) and the fact that NULL pointers
aren't uncommon, it probably wouldn't take long for an attacker to
find the hash that corresponds to 0. Although harder, the same goes
for most common error values, such as -1, -2, -11, -14, etc.
The NULL part actually fixes a regression: NULL pointers weren't
obfuscated until commit 3e5903eb9cff ("vsprintf: Prevent crash when
dereferencing invalid pointers") which went into 5.2. I'm tacking
the IS_ERR() part on here because error pointers won't leak kernel
addresses and printing them as pointers shouldn't be any different
from e.g. %d with PTR_ERR_OR_ZERO(). Obfuscating them just makes
debugging based on existing pr_debug and friends excruciating.
Note that the "always print 0's for %pK when kptr_restrict == 2"
behaviour which goes way back is left as is.
Example output with the patch applied:
ptr error-ptr NULL
%p: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%pK, kptr = 0: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%px: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 1: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 2: 0000000000000000 0000000000000000 0000000000000000
Fixes: 3e5903eb9cff ("vsprintf: Prevent crash when dereferencing invalid pointers")
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-19 13:26:57 +02:00
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2017-11-01 15:32:23 +11:00
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2018-12-04 23:23:11 +02:00
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2017-11-01 15:32:23 +11:00
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2018-12-04 23:23:11 +02:00
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2017-11-01 15:32:23 +11:00
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2018-06-13 19:18:40 +02:00
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2018-12-04 23:23:11 +02:00
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2018-06-13 19:18:40 +02:00
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2017-11-01 15:32:23 +11:00
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2015-11-06 16:30:29 -08:00
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2017-11-01 15:32:23 +11:00
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2015-11-06 16:30:29 -08:00
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2017-11-01 15:32:23 +11:00
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2015-11-06 16:30:29 -08:00
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2018-12-04 23:23:11 +02:00
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vsprintf: don't obfuscate NULL and error pointers
I don't see what security concern is addressed by obfuscating NULL
and IS_ERR() error pointers, printed with %p/%pK. Given the number
of sites where %p is used (over 10000) and the fact that NULL pointers
aren't uncommon, it probably wouldn't take long for an attacker to
find the hash that corresponds to 0. Although harder, the same goes
for most common error values, such as -1, -2, -11, -14, etc.
The NULL part actually fixes a regression: NULL pointers weren't
obfuscated until commit 3e5903eb9cff ("vsprintf: Prevent crash when
dereferencing invalid pointers") which went into 5.2. I'm tacking
the IS_ERR() part on here because error pointers won't leak kernel
addresses and printing them as pointers shouldn't be any different
from e.g. %d with PTR_ERR_OR_ZERO(). Obfuscating them just makes
debugging based on existing pr_debug and friends excruciating.
Note that the "always print 0's for %pK when kptr_restrict == 2"
behaviour which goes way back is left as is.
Example output with the patch applied:
ptr error-ptr NULL
%p: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%pK, kptr = 0: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%px: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 1: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 2: 0000000000000000 0000000000000000 0000000000000000
Fixes: 3e5903eb9cff ("vsprintf: Prevent crash when dereferencing invalid pointers")
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-19 13:26:57 +02:00
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vsprintf: Prevent crash when dereferencing invalid pointers
We already prevent crash when dereferencing some obviously broken
pointers. But the handling is not consistent. Sometimes we print "(null)"
only for pure NULL pointer, sometimes for pointers in the first
page and sometimes also for pointers in the last page (error codes).
Note that printk() call this code under logbuf_lock. Any recursive
printks are redirected to the printk_safe implementation and the messages
are stored into per-CPU buffers. These buffers might be eventually flushed
in printk_safe_flush_on_panic() but it is not guaranteed.
This patch adds a check using probe_kernel_read(). It is not a full-proof
test. But it should help to see the error message in 99% situations where
the kernel would silently crash otherwise.
Also it makes the error handling unified for "%s" and the many %p*
specifiers that need to read the data from a given address. We print:
+ (null) when accessing data on pure pure NULL address
+ (efault) when accessing data on an invalid address
It does not affect the %p* specifiers that just print the given address
in some form, namely %pF, %pf, %pS, %ps, %pB, %pK, %px, and plain %p.
Note that we print (efault) from security reasons. In fact, the real
address can be seen only by %px or eventually %pK.
Link: http://lkml.kernel.org/r/20190417115350.20479-9-pmladek@suse.com
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Tobin C . Harding" <me@tobin.cc>
Cc: Joe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
2019-04-17 13:53:48 +02:00
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|
vsprintf: don't obfuscate NULL and error pointers
I don't see what security concern is addressed by obfuscating NULL
and IS_ERR() error pointers, printed with %p/%pK. Given the number
of sites where %p is used (over 10000) and the fact that NULL pointers
aren't uncommon, it probably wouldn't take long for an attacker to
find the hash that corresponds to 0. Although harder, the same goes
for most common error values, such as -1, -2, -11, -14, etc.
The NULL part actually fixes a regression: NULL pointers weren't
obfuscated until commit 3e5903eb9cff ("vsprintf: Prevent crash when
dereferencing invalid pointers") which went into 5.2. I'm tacking
the IS_ERR() part on here because error pointers won't leak kernel
addresses and printing them as pointers shouldn't be any different
from e.g. %d with PTR_ERR_OR_ZERO(). Obfuscating them just makes
debugging based on existing pr_debug and friends excruciating.
Note that the "always print 0's for %pK when kptr_restrict == 2"
behaviour which goes way back is left as is.
Example output with the patch applied:
ptr error-ptr NULL
%p: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%pK, kptr = 0: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%px: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 1: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 2: 0000000000000000 0000000000000000 0000000000000000
Fixes: 3e5903eb9cff ("vsprintf: Prevent crash when dereferencing invalid pointers")
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-19 13:26:57 +02:00
|
|
|
|
vsprintf: Prevent crash when dereferencing invalid pointers
We already prevent crash when dereferencing some obviously broken
pointers. But the handling is not consistent. Sometimes we print "(null)"
only for pure NULL pointer, sometimes for pointers in the first
page and sometimes also for pointers in the last page (error codes).
Note that printk() call this code under logbuf_lock. Any recursive
printks are redirected to the printk_safe implementation and the messages
are stored into per-CPU buffers. These buffers might be eventually flushed
in printk_safe_flush_on_panic() but it is not guaranteed.
This patch adds a check using probe_kernel_read(). It is not a full-proof
test. But it should help to see the error message in 99% situations where
the kernel would silently crash otherwise.
Also it makes the error handling unified for "%s" and the many %p*
specifiers that need to read the data from a given address. We print:
+ (null) when accessing data on pure pure NULL address
+ (efault) when accessing data on an invalid address
It does not affect the %p* specifiers that just print the given address
in some form, namely %pF, %pf, %pS, %ps, %pB, %pK, %px, and plain %p.
Note that we print (efault) from security reasons. In fact, the real
address can be seen only by %px or eventually %pK.
Link: http://lkml.kernel.org/r/20190417115350.20479-9-pmladek@suse.com
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Tobin C . Harding" <me@tobin.cc>
Cc: Joe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
2019-04-17 13:53:48 +02:00
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|
vsprintf: don't obfuscate NULL and error pointers
I don't see what security concern is addressed by obfuscating NULL
and IS_ERR() error pointers, printed with %p/%pK. Given the number
of sites where %p is used (over 10000) and the fact that NULL pointers
aren't uncommon, it probably wouldn't take long for an attacker to
find the hash that corresponds to 0. Although harder, the same goes
for most common error values, such as -1, -2, -11, -14, etc.
The NULL part actually fixes a regression: NULL pointers weren't
obfuscated until commit 3e5903eb9cff ("vsprintf: Prevent crash when
dereferencing invalid pointers") which went into 5.2. I'm tacking
the IS_ERR() part on here because error pointers won't leak kernel
addresses and printing them as pointers shouldn't be any different
from e.g. %d with PTR_ERR_OR_ZERO(). Obfuscating them just makes
debugging based on existing pr_debug and friends excruciating.
Note that the "always print 0's for %pK when kptr_restrict == 2"
behaviour which goes way back is left as is.
Example output with the patch applied:
ptr error-ptr NULL
%p: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%pK, kptr = 0: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%px: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 1: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 2: 0000000000000000 0000000000000000 0000000000000000
Fixes: 3e5903eb9cff ("vsprintf: Prevent crash when dereferencing invalid pointers")
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-19 13:26:57 +02:00
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vsprintf: Prevent crash when dereferencing invalid pointers
We already prevent crash when dereferencing some obviously broken
pointers. But the handling is not consistent. Sometimes we print "(null)"
only for pure NULL pointer, sometimes for pointers in the first
page and sometimes also for pointers in the last page (error codes).
Note that printk() call this code under logbuf_lock. Any recursive
printks are redirected to the printk_safe implementation and the messages
are stored into per-CPU buffers. These buffers might be eventually flushed
in printk_safe_flush_on_panic() but it is not guaranteed.
This patch adds a check using probe_kernel_read(). It is not a full-proof
test. But it should help to see the error message in 99% situations where
the kernel would silently crash otherwise.
Also it makes the error handling unified for "%s" and the many %p*
specifiers that need to read the data from a given address. We print:
+ (null) when accessing data on pure pure NULL address
+ (efault) when accessing data on an invalid address
It does not affect the %p* specifiers that just print the given address
in some form, namely %pF, %pf, %pS, %ps, %pB, %pK, %px, and plain %p.
Note that we print (efault) from security reasons. In fact, the real
address can be seen only by %px or eventually %pK.
Link: http://lkml.kernel.org/r/20190417115350.20479-9-pmladek@suse.com
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Tobin C . Harding" <me@tobin.cc>
Cc: Joe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
2019-04-17 13:53:48 +02:00
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2015-11-06 16:30:29 -08:00
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2017-11-01 15:32:23 +11:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:59:09 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:59:09 -08:00
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2019-08-09 09:24:57 +08:00
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2016-01-15 16:59:09 -08:00
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2015-11-06 16:30:29 -08:00
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2018-12-04 23:23:11 +02:00
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2020-04-15 20:00:44 +03:00
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2018-12-04 23:23:11 +02:00
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2020-04-15 20:00:44 +03:00
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2018-12-04 23:23:11 +02:00
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2020-04-15 20:00:44 +03:00
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2018-12-04 23:23:11 +02:00
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2020-04-15 20:00:44 +03:00
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2018-12-04 23:23:11 +02:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:59:06 -08:00
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2019-03-04 12:00:09 +02:00
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2016-01-15 16:59:06 -08:00
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2019-03-04 12:00:09 +02:00
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2016-01-15 16:59:06 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:59:06 -08:00
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2015-11-06 16:30:29 -08:00
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mm, printk: introduce new format string for flags
In mm we use several kinds of flags bitfields that are sometimes printed
for debugging purposes, or exported to userspace via sysfs. To make
them easier to interpret independently on kernel version and config, we
want to dump also the symbolic flag names. So far this has been done
with repeated calls to pr_cont(), which is unreliable on SMP, and not
usable for e.g. sysfs export.
To get a more reliable and universal solution, this patch extends
printk() format string for pointers to handle the page flags (%pGp),
gfp_flags (%pGg) and vma flags (%pGv). Existing users of
dump_flag_names() are converted and simplified.
It would be possible to pass flags by value instead of pointer, but the
%p format string for pointers already has extensions for various kernel
structures, so it's a good fit, and the extra indirection in a
non-critical path is negligible.
[linux@rasmusvillemoes.dk: lots of good implementation suggestions]
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-15 14:55:56 -07:00
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2019-10-03 15:32:19 +03:00
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2020-05-24 17:30:40 +02:00
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2019-10-03 15:32:19 +03:00
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printf: add support for printing symbolic error names
It has been suggested several times to extend vsnprintf() to be able
to convert the numeric value of ENOSPC to print "ENOSPC". This
implements that as a %p extension: With %pe, one can do
if (IS_ERR(foo)) {
pr_err("Sorry, can't do that: %pe\n", foo);
return PTR_ERR(foo);
}
instead of what is seen in quite a few places in the kernel:
if (IS_ERR(foo)) {
pr_err("Sorry, can't do that: %ld\n", PTR_ERR(foo));
return PTR_ERR(foo);
}
If the value passed to %pe is an ERR_PTR, but the library function
errname() added here doesn't know about the value, the value is simply
printed in decimal. If the value passed to %pe is not an ERR_PTR, we
treat it as an ordinary %p and thus print the hashed value (passing
non-ERR_PTR values to %pe indicates a bug in the caller, but we can't
do much about that).
With my embedded hat on, and because it's not very invasive to do,
I've made it possible to remove this. The errname() function and
associated lookup tables take up about 3K. For most, that's probably
quite acceptable and a price worth paying for more readable
dmesg (once this starts getting used), while for those that disable
printk() it's of very little use - I don't see a
procfs/sysfs/seq_printf() file reasonably making use of this - and
they clearly want to squeeze vmlinux as much as possible. Hence the
default y if PRINTK.
The symbols to include have been found by massaging the output of
find arch include -iname 'errno*.h' | xargs grep -E 'define\s*E'
In the cases where some common aliasing exists
(e.g. EAGAIN=EWOULDBLOCK on all platforms, EDEADLOCK=EDEADLK on most),
I've moved the more popular one (in terms of 'git grep -w Efoo | wc)
to the bottom so that one takes precedence.
Link: http://lkml.kernel.org/r/20191015190706.15989-1-linux@rasmusvillemoes.dk
To: "Jonathan Corbet" <corbet@lwn.net>
To: linux-kernel@vger.kernel.org
Cc: "Andy Shevchenko" <andy.shevchenko@gmail.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>
Cc: "Joe Perches" <joe@perches.com>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
[andy.shevchenko@gmail.com: use abs()]
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
2019-10-15 21:07:05 +02:00
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2015-11-06 16:30:29 -08:00
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vsprintf: Prevent crash when dereferencing invalid pointers
We already prevent crash when dereferencing some obviously broken
pointers. But the handling is not consistent. Sometimes we print "(null)"
only for pure NULL pointer, sometimes for pointers in the first
page and sometimes also for pointers in the last page (error codes).
Note that printk() call this code under logbuf_lock. Any recursive
printks are redirected to the printk_safe implementation and the messages
are stored into per-CPU buffers. These buffers might be eventually flushed
in printk_safe_flush_on_panic() but it is not guaranteed.
This patch adds a check using probe_kernel_read(). It is not a full-proof
test. But it should help to see the error message in 99% situations where
the kernel would silently crash otherwise.
Also it makes the error handling unified for "%s" and the many %p*
specifiers that need to read the data from a given address. We print:
+ (null) when accessing data on pure pure NULL address
+ (efault) when accessing data on an invalid address
It does not affect the %p* specifiers that just print the given address
in some form, namely %pF, %pf, %pS, %ps, %pB, %pK, %px, and plain %p.
Note that we print (efault) from security reasons. In fact, the real
address can be seen only by %px or eventually %pK.
Link: http://lkml.kernel.org/r/20190417115350.20479-9-pmladek@suse.com
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Tobin C . Harding" <me@tobin.cc>
Cc: Joe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
2019-04-17 13:53:48 +02:00
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vsprintf: don't obfuscate NULL and error pointers
I don't see what security concern is addressed by obfuscating NULL
and IS_ERR() error pointers, printed with %p/%pK. Given the number
of sites where %p is used (over 10000) and the fact that NULL pointers
aren't uncommon, it probably wouldn't take long for an attacker to
find the hash that corresponds to 0. Although harder, the same goes
for most common error values, such as -1, -2, -11, -14, etc.
The NULL part actually fixes a regression: NULL pointers weren't
obfuscated until commit 3e5903eb9cff ("vsprintf: Prevent crash when
dereferencing invalid pointers") which went into 5.2. I'm tacking
the IS_ERR() part on here because error pointers won't leak kernel
addresses and printing them as pointers shouldn't be any different
from e.g. %d with PTR_ERR_OR_ZERO(). Obfuscating them just makes
debugging based on existing pr_debug and friends excruciating.
Note that the "always print 0's for %pK when kptr_restrict == 2"
behaviour which goes way back is left as is.
Example output with the patch applied:
ptr error-ptr NULL
%p: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%pK, kptr = 0: 0000000001f8cc5b fffffffffffffff2 0000000000000000
%px: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 1: ffff888048c04020 fffffffffffffff2 0000000000000000
%pK, kptr = 2: 0000000000000000 0000000000000000 0000000000000000
Fixes: 3e5903eb9cff ("vsprintf: Prevent crash when dereferencing invalid pointers")
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-05-19 13:26:57 +02:00
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vsprintf: Prevent crash when dereferencing invalid pointers
We already prevent crash when dereferencing some obviously broken
pointers. But the handling is not consistent. Sometimes we print "(null)"
only for pure NULL pointer, sometimes for pointers in the first
page and sometimes also for pointers in the last page (error codes).
Note that printk() call this code under logbuf_lock. Any recursive
printks are redirected to the printk_safe implementation and the messages
are stored into per-CPU buffers. These buffers might be eventually flushed
in printk_safe_flush_on_panic() but it is not guaranteed.
This patch adds a check using probe_kernel_read(). It is not a full-proof
test. But it should help to see the error message in 99% situations where
the kernel would silently crash otherwise.
Also it makes the error handling unified for "%s" and the many %p*
specifiers that need to read the data from a given address. We print:
+ (null) when accessing data on pure pure NULL address
+ (efault) when accessing data on an invalid address
It does not affect the %p* specifiers that just print the given address
in some form, namely %pF, %pf, %pS, %ps, %pB, %pK, %px, and plain %p.
Note that we print (efault) from security reasons. In fact, the real
address can be seen only by %px or eventually %pK.
Link: http://lkml.kernel.org/r/20190417115350.20479-9-pmladek@suse.com
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Tobin C . Harding" <me@tobin.cc>
Cc: Joe Perches <joe@perches.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
2019-04-17 13:53:48 +02:00
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2015-11-06 16:30:29 -08:00
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2020-04-15 20:00:44 +03:00
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2015-11-06 16:30:29 -08:00
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mm, printk: introduce new format string for flags
In mm we use several kinds of flags bitfields that are sometimes printed
for debugging purposes, or exported to userspace via sysfs. To make
them easier to interpret independently on kernel version and config, we
want to dump also the symbolic flag names. So far this has been done
with repeated calls to pr_cont(), which is unreliable on SMP, and not
usable for e.g. sysfs export.
To get a more reliable and universal solution, this patch extends
printk() format string for pointers to handle the page flags (%pGp),
gfp_flags (%pGg) and vma flags (%pGv). Existing users of
dump_flag_names() are converted and simplified.
It would be possible to pass flags by value instead of pointer, but the
%p format string for pointers already has extensions for various kernel
structures, so it's a good fit, and the extra indirection in a
non-critical path is negligible.
[linux@rasmusvillemoes.dk: lots of good implementation suggestions]
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-15 14:55:56 -07:00
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printf: add support for printing symbolic error names
It has been suggested several times to extend vsnprintf() to be able
to convert the numeric value of ENOSPC to print "ENOSPC". This
implements that as a %p extension: With %pe, one can do
if (IS_ERR(foo)) {
pr_err("Sorry, can't do that: %pe\n", foo);
return PTR_ERR(foo);
}
instead of what is seen in quite a few places in the kernel:
if (IS_ERR(foo)) {
pr_err("Sorry, can't do that: %ld\n", PTR_ERR(foo));
return PTR_ERR(foo);
}
If the value passed to %pe is an ERR_PTR, but the library function
errname() added here doesn't know about the value, the value is simply
printed in decimal. If the value passed to %pe is not an ERR_PTR, we
treat it as an ordinary %p and thus print the hashed value (passing
non-ERR_PTR values to %pe indicates a bug in the caller, but we can't
do much about that).
With my embedded hat on, and because it's not very invasive to do,
I've made it possible to remove this. The errname() function and
associated lookup tables take up about 3K. For most, that's probably
quite acceptable and a price worth paying for more readable
dmesg (once this starts getting used), while for those that disable
printk() it's of very little use - I don't see a
procfs/sysfs/seq_printf() file reasonably making use of this - and
they clearly want to squeeze vmlinux as much as possible. Hence the
default y if PRINTK.
The symbols to include have been found by massaging the output of
find arch include -iname 'errno*.h' | xargs grep -E 'define\s*E'
In the cases where some common aliasing exists
(e.g. EAGAIN=EWOULDBLOCK on all platforms, EDEADLOCK=EDEADLK on most),
I've moved the more popular one (in terms of 'git grep -w Efoo | wc)
to the bottom so that one takes precedence.
Link: http://lkml.kernel.org/r/20191015190706.15989-1-linux@rasmusvillemoes.dk
To: "Jonathan Corbet" <corbet@lwn.net>
To: linux-kernel@vger.kernel.org
Cc: "Andy Shevchenko" <andy.shevchenko@gmail.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>
Cc: "Joe Perches" <joe@perches.com>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
[andy.shevchenko@gmail.com: use abs()]
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
2019-10-15 21:07:05 +02:00
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2019-10-03 15:32:19 +03:00
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2015-11-06 16:30:29 -08:00
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2019-04-05 12:58:57 +11:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:53 -08:00
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2019-04-05 12:58:57 +11:00
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2016-01-15 16:58:53 -08:00
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2015-11-06 16:30:29 -08:00
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2016-01-15 16:58:53 -08:00
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2015-11-06 16:30:29 -08:00
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2019-04-05 12:58:57 +11:00
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2015-11-06 16:30:29 -08:00
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