2005-04-16 15:20:36 -07:00
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2008-10-27 15:19:48 +00:00
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2005-04-16 15:20:36 -07:00
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2007-07-16 09:46:31 +02:00
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2005-04-16 15:20:36 -07:00
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2008-04-24 07:44:08 -04:00
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2005-04-16 15:20:36 -07:00
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2005-09-16 19:28:13 -07:00
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2006-07-14 00:24:43 -07:00
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2008-02-08 04:18:31 -08:00
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2007-10-18 23:40:14 -07:00
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2009-05-04 12:51:14 -06:00
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2008-07-25 19:45:49 -07:00
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2011-11-14 15:56:38 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2007-07-16 09:46:31 +02:00
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2005-04-16 15:20:36 -07:00
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2011-01-12 17:00:32 -08:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2011-01-12 17:00:32 -08:00
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2005-04-16 15:20:36 -07:00
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2011-05-26 16:25:51 -07:00
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2009-12-17 13:16:30 +01:00
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2014-04-07 15:38:46 -07:00
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2005-04-16 15:20:36 -07:00
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2007-07-16 09:46:31 +02:00
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2005-04-16 15:20:36 -07:00
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2014-01-23 15:55:35 -08:00
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2005-04-16 15:20:36 -07:00
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2014-01-23 15:55:35 -08:00
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2009-12-17 13:16:30 +01:00
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2014-01-23 15:55:35 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2012-08-11 12:38:26 -07:00
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2005-04-16 15:20:36 -07:00
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2005-09-09 13:04:10 -07:00
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2008-11-14 10:39:19 +11:00
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2007-10-18 23:40:14 -07:00
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2005-04-16 15:20:36 -07:00
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2006-10-02 02:18:54 -07:00
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2007-10-18 23:40:14 -07:00
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2008-07-25 19:45:49 -07:00
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2011-06-17 16:50:40 +02:00
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2008-07-25 19:45:49 -07:00
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CRED: Fix get_task_cred() and task_state() to not resurrect dead credentials
It's possible for get_task_cred() as it currently stands to 'corrupt' a set of
credentials by incrementing their usage count after their replacement by the
task being accessed.
What happens is that get_task_cred() can race with commit_creds():
TASK_1 TASK_2 RCU_CLEANER
-->get_task_cred(TASK_2)
rcu_read_lock()
__cred = __task_cred(TASK_2)
-->commit_creds()
old_cred = TASK_2->real_cred
TASK_2->real_cred = ...
put_cred(old_cred)
call_rcu(old_cred)
[__cred->usage == 0]
get_cred(__cred)
[__cred->usage == 1]
rcu_read_unlock()
-->put_cred_rcu()
[__cred->usage == 1]
panic()
However, since a tasks credentials are generally not changed very often, we can
reasonably make use of a loop involving reading the creds pointer and using
atomic_inc_not_zero() to attempt to increment it if it hasn't already hit zero.
If successful, we can safely return the credentials in the knowledge that, even
if the task we're accessing has released them, they haven't gone to the RCU
cleanup code.
We then change task_state() in procfs to use get_task_cred() rather than
calling get_cred() on the result of __task_cred(), as that suffers from the
same problem.
Without this change, a BUG_ON in __put_cred() or in put_cred_rcu() can be
tripped when it is noticed that the usage count is not zero as it ought to be,
for example:
kernel BUG at kernel/cred.c:168!
invalid opcode: 0000 [#1] SMP
last sysfs file: /sys/kernel/mm/ksm/run
CPU 0
Pid: 2436, comm: master Not tainted 2.6.33.3-85.fc13.x86_64 #1 0HR330/OptiPlex
745
RIP: 0010:[<ffffffff81069881>] [<ffffffff81069881>] __put_cred+0xc/0x45
RSP: 0018:ffff88019e7e9eb8 EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffff880161514480 RCX: 00000000ffffffff
RDX: 00000000ffffffff RSI: ffff880140c690c0 RDI: ffff880140c690c0
RBP: ffff88019e7e9eb8 R08: 00000000000000d0 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000040 R12: ffff880140c690c0
R13: ffff88019e77aea0 R14: 00007fff336b0a5c R15: 0000000000000001
FS: 00007f12f50d97c0(0000) GS:ffff880007400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8f461bc000 CR3: 00000001b26ce000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process master (pid: 2436, threadinfo ffff88019e7e8000, task ffff88019e77aea0)
Stack:
ffff88019e7e9ec8 ffffffff810698cd ffff88019e7e9ef8 ffffffff81069b45
<0> ffff880161514180 ffff880161514480 ffff880161514180 0000000000000000
<0> ffff88019e7e9f28 ffffffff8106aace 0000000000000001 0000000000000246
Call Trace:
[<ffffffff810698cd>] put_cred+0x13/0x15
[<ffffffff81069b45>] commit_creds+0x16b/0x175
[<ffffffff8106aace>] set_current_groups+0x47/0x4e
[<ffffffff8106ac89>] sys_setgroups+0xf6/0x105
[<ffffffff81009b02>] system_call_fastpath+0x16/0x1b
Code: 48 8d 71 ff e8 7e 4e 15 00 85 c0 78 0b 8b 75 ec 48 89 df e8 ef 4a 15 00
48 83 c4 18 5b c9 c3 55 8b 07 8b 07 48 89 e5 85 c0 74 04 <0f> 0b eb fe 65 48 8b
04 25 00 cc 00 00 48 3b b8 58 04 00 00 75
RIP [<ffffffff81069881>] __put_cred+0xc/0x45
RSP <ffff88019e7e9eb8>
---[ end trace df391256a100ebdd ]---
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-07-29 12:45:49 +01:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2013-10-07 11:29:22 +01:00
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2005-04-16 15:20:36 -07:00
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2007-10-18 23:40:14 -07:00
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2013-10-07 11:29:22 +01:00
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2008-02-08 04:18:33 -08:00
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2007-10-18 23:40:14 -07:00
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2012-02-09 08:48:21 -08:00
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2006-10-02 02:18:54 -07:00
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2005-04-16 15:20:36 -07:00
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2005-09-09 13:04:10 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2005-09-09 13:04:10 -07:00
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2005-09-16 19:28:13 -07:00
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2005-04-16 15:20:36 -07:00
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2008-11-14 10:39:19 +11:00
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2005-04-16 15:20:36 -07:00
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2012-12-17 16:03:17 -08:00
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2011-11-14 15:56:38 -08:00
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2008-11-14 10:39:19 +11:00
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2005-04-16 15:20:36 -07:00
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2011-01-12 17:00:32 -08:00
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2005-04-16 15:20:36 -07:00
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2012-12-17 16:05:02 -08:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2011-01-12 17:00:32 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2011-01-12 17:00:32 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2006-10-02 02:18:52 -07:00
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2005-04-16 15:20:36 -07:00
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2006-10-02 02:18:52 -07:00
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2005-04-16 15:20:36 -07:00
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2010-05-26 14:43:22 -07:00
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2010-02-22 17:04:52 -08:00
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2008-11-14 10:39:19 +11:00
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2010-02-22 17:04:52 -08:00
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2010-03-05 13:42:42 -08:00
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2006-10-02 02:18:52 -07:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2008-02-04 22:29:42 -08:00
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2011-01-12 17:00:32 -08:00
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2008-02-04 22:29:42 -08:00
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2008-02-08 04:18:33 -08:00
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2014-07-23 15:36:26 -04:00
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2008-02-04 22:29:42 -08:00
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2011-01-12 17:00:32 -08:00
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2008-02-04 22:29:42 -08:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-11-14 10:39:19 +11:00
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2008-11-14 10:39:16 +11:00
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2008-11-14 10:39:19 +11:00
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2005-04-16 15:20:36 -07:00
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2012-12-17 16:03:14 -08:00
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2008-02-08 04:18:33 -08:00
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2007-07-15 23:40:48 -07:00
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2008-02-08 04:18:33 -08:00
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2007-07-15 23:40:48 -07:00
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2009-09-21 11:06:27 +02:00
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2011-01-12 17:00:32 -08:00
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2009-09-21 11:06:27 +02:00
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2011-01-12 17:00:32 -08:00
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2009-09-21 11:06:27 +02:00
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2011-01-12 17:00:32 -08:00
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2009-09-21 11:06:27 +02:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2007-07-16 09:46:31 +02:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:33 -08:00
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2012-12-17 16:03:14 -08:00
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2009-09-21 11:06:27 +02:00
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2008-02-08 04:18:33 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:31 -08:00
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2005-04-16 15:20:36 -07:00
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fs/proc, core/debug: Don't expose absolute kernel addresses via wchan
commit b2f73922d119686323f14fbbe46587f863852328 upstream.
So the /proc/PID/stat 'wchan' field (the 30th field, which contains
the absolute kernel address of the kernel function a task is blocked in)
leaks absolute kernel addresses to unprivileged user-space:
seq_put_decimal_ull(m, ' ', wchan);
The absolute address might also leak via /proc/PID/wchan as well, if
KALLSYMS is turned off or if the symbol lookup fails for some reason:
static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
unsigned long wchan;
char symname[KSYM_NAME_LEN];
wchan = get_wchan(task);
if (lookup_symbol_name(wchan, symname) < 0) {
if (!ptrace_may_access(task, PTRACE_MODE_READ))
return 0;
seq_printf(m, "%lu", wchan);
} else {
seq_printf(m, "%s", symname);
}
return 0;
}
This isn't ideal, because for example it trivially leaks the KASLR offset
to any local attacker:
fomalhaut:~> printf "%016lx\n" $(cat /proc/$$/stat | cut -d' ' -f35)
ffffffff8123b380
Most real-life uses of wchan are symbolic:
ps -eo pid:10,tid:10,wchan:30,comm
and procps uses /proc/PID/wchan, not the absolute address in /proc/PID/stat:
triton:~/tip> strace -f ps -eo pid:10,tid:10,wchan:30,comm 2>&1 | grep wchan | tail -1
open("/proc/30833/wchan", O_RDONLY) = 6
There's one compatibility quirk here: procps relies on whether the
absolute value is non-zero - and we can provide that functionality
by outputing "0" or "1" depending on whether the task is blocked
(whether there's a wchan address).
These days there appears to be very little legitimate reason
user-space would be interested in the absolute address. The
absolute address is mostly historic: from the days when we
didn't have kallsyms and user-space procps had to do the
decoding itself via the System.map.
So this patch sets all numeric output to "0" or "1" and keeps only
symbolic output, in /proc/PID/wchan.
( The absolute sleep address can generally still be profiled via
perf, by tasks with sufficient privileges. )
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: kasan-dev <kasan-dev@googlegroups.com>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20150930135917.GA3285@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[ kamal: backport to 3.16-stable: proc_pid_wchan context ]
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
2015-09-30 15:59:17 +02:00
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2012-05-31 16:26:19 -07:00
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2005-04-16 15:20:36 -07:00
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2007-07-16 09:46:31 +02:00
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2005-04-16 15:20:36 -07:00
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2009-05-04 12:51:14 -06:00
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2005-04-16 15:20:36 -07:00
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2007-08-23 15:18:02 +02:00
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2007-10-15 17:00:19 +02:00
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2005-04-16 15:20:36 -07:00
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2006-10-02 02:18:53 -07:00
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2005-04-16 15:20:36 -07:00
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2012-01-03 12:25:15 -05:00
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2005-04-16 15:20:36 -07:00
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2009-05-04 12:51:14 -06:00
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2005-04-16 15:20:36 -07:00
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2011-12-15 14:56:09 +01:00
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2006-09-29 02:00:41 -07:00
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2006-10-02 02:18:53 -07:00
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2006-12-08 02:36:07 -08:00
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2008-04-30 00:53:31 -07:00
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2006-12-08 02:36:07 -08:00
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2006-10-02 02:18:53 -07:00
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2010-05-26 14:43:22 -07:00
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2005-04-16 15:20:36 -07:00
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2006-10-02 02:18:53 -07:00
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2007-10-15 17:00:19 +02:00
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2010-03-05 13:42:42 -08:00
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2006-10-02 02:18:53 -07:00
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2005-04-16 15:20:36 -07:00
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2006-10-02 02:18:53 -07:00
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2005-04-16 15:20:36 -07:00
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2012-11-13 14:20:55 +01:00
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2014-01-23 15:55:53 -08:00
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2005-04-16 15:20:36 -07:00
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2006-10-02 02:18:53 -07:00
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2012-11-21 16:26:44 +01:00
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2011-12-15 14:56:09 +01:00
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2005-04-16 15:20:36 -07:00
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2006-10-02 02:18:53 -07:00
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2007-10-18 23:40:14 -07:00
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2008-01-15 00:02:37 +03:00
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2007-10-18 23:40:14 -07:00
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2006-10-02 02:18:53 -07:00
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2005-04-16 15:20:36 -07:00
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2009-05-04 12:51:14 -06:00
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2005-04-16 15:20:36 -07:00
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2012-11-21 16:26:44 +01:00
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2012-11-13 14:20:55 +01:00
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2005-04-16 15:20:36 -07:00
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2007-07-15 23:39:42 -07:00
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2005-04-16 15:20:36 -07:00
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2012-03-23 15:02:54 -07:00
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2012-05-31 16:26:19 -07:00
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2012-03-23 15:02:54 -07:00
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fs/proc, core/debug: Don't expose absolute kernel addresses via wchan
commit b2f73922d119686323f14fbbe46587f863852328 upstream.
So the /proc/PID/stat 'wchan' field (the 30th field, which contains
the absolute kernel address of the kernel function a task is blocked in)
leaks absolute kernel addresses to unprivileged user-space:
seq_put_decimal_ull(m, ' ', wchan);
The absolute address might also leak via /proc/PID/wchan as well, if
KALLSYMS is turned off or if the symbol lookup fails for some reason:
static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
unsigned long wchan;
char symname[KSYM_NAME_LEN];
wchan = get_wchan(task);
if (lookup_symbol_name(wchan, symname) < 0) {
if (!ptrace_may_access(task, PTRACE_MODE_READ))
return 0;
seq_printf(m, "%lu", wchan);
} else {
seq_printf(m, "%s", symname);
}
return 0;
}
This isn't ideal, because for example it trivially leaks the KASLR offset
to any local attacker:
fomalhaut:~> printf "%016lx\n" $(cat /proc/$$/stat | cut -d' ' -f35)
ffffffff8123b380
Most real-life uses of wchan are symbolic:
ps -eo pid:10,tid:10,wchan:30,comm
and procps uses /proc/PID/wchan, not the absolute address in /proc/PID/stat:
triton:~/tip> strace -f ps -eo pid:10,tid:10,wchan:30,comm 2>&1 | grep wchan | tail -1
open("/proc/30833/wchan", O_RDONLY) = 6
There's one compatibility quirk here: procps relies on whether the
absolute value is non-zero - and we can provide that functionality
by outputing "0" or "1" depending on whether the task is blocked
(whether there's a wchan address).
These days there appears to be very little legitimate reason
user-space would be interested in the absolute address. The
absolute address is mostly historic: from the days when we
didn't have kallsyms and user-space procps had to do the
decoding itself via the System.map.
So this patch sets all numeric output to "0" or "1" and keeps only
symbolic output, in /proc/PID/wchan.
( The absolute sleep address can generally still be profiled via
perf, by tasks with sufficient privileges. )
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Kostya Serebryany <kcc@google.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: kasan-dev <kasan-dev@googlegroups.com>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20150930135917.GA3285@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[ kamal: backport to 3.16-stable: proc_pid_wchan context ]
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
2015-09-30 15:59:17 +02:00
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2012-03-23 15:02:54 -07:00
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2012-05-31 16:26:44 -07:00
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2012-03-23 15:02:54 -07:00
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2007-07-16 09:46:31 +02:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:31 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:31 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:31 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:31 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:31 -08:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:32 -08:00
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2005-04-16 15:20:36 -07:00
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2011-01-12 17:00:32 -08:00
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2005-04-16 15:20:36 -07:00
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2007-07-16 09:46:31 +02:00
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2005-04-16 15:20:36 -07:00
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2012-03-23 15:02:54 -07:00
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2012-03-28 14:42:39 -07:00
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2012-03-23 15:02:54 -07:00
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2005-04-16 15:20:36 -07:00
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2008-02-08 04:18:32 -08:00
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2005-04-16 15:20:36 -07:00
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2012-05-31 16:26:43 -07:00
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