2018-10-17 16:45:32 -07:00
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2019-02-24 21:05:27 +01:00
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2018-10-17 16:45:32 -07:00
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2020-03-14 15:29:50 -07:00
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2018-10-17 16:45:32 -07:00
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2021-09-25 16:34:55 +02:00
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2018-10-17 16:45:32 -07:00
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overflow: Implement size_t saturating arithmetic helpers
In order to perform more open-coded replacements of common allocation
size arithmetic, the kernel needs saturating (SIZE_MAX) helpers for
multiplication, addition, and subtraction. For example, it is common in
allocators, especially on realloc, to add to an existing size:
p = krealloc(map->patch,
sizeof(struct reg_sequence) * (map->patch_regs + num_regs),
GFP_KERNEL);
There is no existing saturating replacement for this calculation, and
just leaving the addition open coded inside array_size() could
potentially overflow as well. For example, an overflow in an expression
for a size_t argument might wrap to zero:
array_size(anything, something_at_size_max + 1) == 0
Introduce size_mul(), size_add(), and size_sub() helpers that
implicitly promote arguments to size_t and saturated calculations for
use in allocations. With these helpers it is also possible to redefine
array_size(), array3_size(), flex_array_size(), and struct_size() in
terms of the new helpers.
As with the check_*_overflow() helpers, the new helpers use __must_check,
though what is really desired is a way to make sure that assignment is
only to a size_t lvalue. Without this, it's still possible to introduce
overflow/underflow via type conversion (i.e. from size_t to int).
Enforcing this will currently need to be left to static analysis or
future use of -Wconversion.
Additionally update the overflow unit tests to force runtime evaluation
for the pathological cases.
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Len Baker <len.baker@gmx.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
2021-09-18 15:17:53 -07:00
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2018-10-17 16:45:32 -07:00
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2023-06-25 22:12:24 +02:00
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2018-10-17 16:45:32 -07:00
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2020-06-08 16:37:11 -05:00
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overflow: Implement size_t saturating arithmetic helpers
In order to perform more open-coded replacements of common allocation
size arithmetic, the kernel needs saturating (SIZE_MAX) helpers for
multiplication, addition, and subtraction. For example, it is common in
allocators, especially on realloc, to add to an existing size:
p = krealloc(map->patch,
sizeof(struct reg_sequence) * (map->patch_regs + num_regs),
GFP_KERNEL);
There is no existing saturating replacement for this calculation, and
just leaving the addition open coded inside array_size() could
potentially overflow as well. For example, an overflow in an expression
for a size_t argument might wrap to zero:
array_size(anything, something_at_size_max + 1) == 0
Introduce size_mul(), size_add(), and size_sub() helpers that
implicitly promote arguments to size_t and saturated calculations for
use in allocations. With these helpers it is also possible to redefine
array_size(), array3_size(), flex_array_size(), and struct_size() in
terms of the new helpers.
As with the check_*_overflow() helpers, the new helpers use __must_check,
though what is really desired is a way to make sure that assignment is
only to a size_t lvalue. Without this, it's still possible to introduce
overflow/underflow via type conversion (i.e. from size_t to int).
Enforcing this will currently need to be left to static analysis or
future use of -Wconversion.
Additionally update the overflow unit tests to force runtime evaluation
for the pathological cases.
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Len Baker <len.baker@gmx.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
2021-09-18 15:17:53 -07:00
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2018-10-17 16:45:32 -07:00
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2020-03-10 11:27:22 -06:00
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2018-10-17 16:45:32 -07:00
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2020-03-10 11:27:22 -06:00
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2018-10-17 16:45:32 -07:00
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2020-10-15 16:17:31 -07:00
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2018-10-17 16:45:32 -07:00
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2026-03-23 01:27:25 +00:00
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string: Introduce strtomem() and strtomem_pad()
One of the "legitimate" uses of strncpy() is copying a NUL-terminated
string into a fixed-size non-NUL-terminated character array. To avoid
the weaknesses and ambiguity of intent when using strncpy(), provide
replacement functions that explicitly distinguish between trailing
padding and not, and require the destination buffer size be discoverable
by the compiler.
For example:
struct obj {
int foo;
char small[4] __nonstring;
char big[8] __nonstring;
int bar;
};
struct obj p;
/* This will truncate to 4 chars with no trailing NUL */
strncpy(p.small, "hello", sizeof(p.small));
/* p.small contains 'h', 'e', 'l', 'l' */
/* This will NUL pad to 8 chars. */
strncpy(p.big, "hello", sizeof(p.big));
/* p.big contains 'h', 'e', 'l', 'l', 'o', '\0', '\0', '\0' */
When the "__nonstring" attributes are missing, the intent of the
programmer becomes ambiguous for whether the lack of a trailing NUL
in the p.small copy is a bug. Additionally, it's not clear whether
the trailing padding in the p.big copy is _needed_. Both cases
become unambiguous with:
strtomem(p.small, "hello");
strtomem_pad(p.big, "hello", 0);
See also https://github.com/KSPP/linux/issues/90
Expand the memcpy KUnit tests to include these functions.
Cc: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Kees Cook <keescook@chromium.org>
2022-08-26 11:04:43 -07:00
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2026-03-23 01:27:25 +00:00
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2018-10-17 16:45:32 -07:00
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2026-03-23 01:27:25 +00:00
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2018-10-17 16:45:32 -07:00
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2020-10-15 16:17:31 -07:00
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2018-10-17 16:45:32 -07:00
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2020-03-04 23:03:47 -08:00
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2021-07-23 13:05:26 -07:00
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2020-03-04 23:03:47 -08:00
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2018-10-17 16:45:32 -07:00
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2019-06-06 19:46:17 -05:00
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2020-03-04 11:03:24 -08:00
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2019-10-05 09:46:43 -07:00
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2019-06-06 19:46:17 -05:00
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2020-03-04 11:03:24 -08:00
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2019-10-05 09:46:43 -07:00
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2020-03-04 11:03:24 -08:00
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2019-10-05 09:46:43 -07:00
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2020-03-04 11:03:24 -08:00
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2020-06-08 16:37:11 -05:00
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2020-08-31 20:09:49 -05:00
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2020-06-08 16:37:11 -05:00
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2020-08-31 20:09:49 -05:00
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2023-01-06 12:06:04 -08:00
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slab: Introduce kmalloc_obj() and family
Introduce type-aware kmalloc-family helpers to replace the common
idioms for single object and arrays of objects allocation:
ptr = kmalloc(sizeof(*ptr), gfp);
ptr = kmalloc(sizeof(struct some_obj_name), gfp);
ptr = kzalloc(sizeof(*ptr), gfp);
ptr = kmalloc_array(count, sizeof(*ptr), gfp);
ptr = kcalloc(count, sizeof(*ptr), gfp);
These become, respectively:
ptr = kmalloc_obj(*ptr, gfp);
ptr = kmalloc_obj(*ptr, gfp);
ptr = kzalloc_obj(*ptr, gfp);
ptr = kmalloc_objs(*ptr, count, gfp);
ptr = kzalloc_objs(*ptr, count, gfp);
Beyond the other benefits outlined below, the primary ergonomic benefit
is the elimination of needing "sizeof" nor the type name, and the
enforcement of assignment types (they do not return "void *", but rather
a pointer to the type of the first argument). The type name _can_ be
used, though, in the case where an assignment is indirect (e.g. via
"return"). This additionally allows[1] variables to be declared via
__auto_type:
__auto_type ptr = kmalloc_obj(struct foo, gfp);
Internal introspection of the allocated type now becomes possible,
allowing for future alignment-aware choices to be made by the allocator
and future hardening work that can be type sensitive. For example,
adding __alignof(*ptr) as an argument to the internal allocators so that
appropriate/efficient alignment choices can be made, or being able to
correctly choose per-allocation offset randomization within a bucket
that does not break alignment requirements.
Link: https://lore.kernel.org/all/CAHk-=wiCOTW5UftUrAnvJkr6769D29tF7Of79gUjdQHS_TkF5A@mail.gmail.com/ [1]
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://patch.msgid.link/20251203233036.3212363-1-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
2025-12-03 15:30:31 -08:00
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slab: Introduce kmalloc_flex() and family
As done for kmalloc_obj*(), introduce a type-aware allocator for flexible
arrays, which may also have "counted_by" annotations:
ptr = kmalloc(struct_size(ptr, flex_member, count), gfp);
becomes:
ptr = kmalloc_flex(*ptr, flex_member, count, gfp);
The internal use of __flex_counter() allows for automatically setting
the counter member of a struct's flexible array member when it has
been annotated with __counted_by(), avoiding any missed early size
initializations while __counted_by() annotations are added to the
kernel. Additionally, this also checks for "too large" allocations based
on the type size of the counter variable. For example:
if (count > type_max(ptr->flex_counter))
fail...;
size = struct_size(ptr, flex_member, count);
ptr = kmalloc(size, gfp);
if (!ptr)
fail...;
ptr->flex_counter = count;
becomes (n.b. unchanged from earlier example):
ptr = kmalloc_flex(*ptr, flex_member, count, gfp);
if (!ptr)
fail...;
ptr->flex_counter = count;
Note that manual initialization of the flexible array counter is still
required (at some point) after allocation as not all compiler versions
support the __counted_by annotation yet. But doing it internally makes
sure they cannot be missed when __counted_by _is_ available, meaning
that the bounds checker will not trip due to the lack of "early enough"
initializations that used to work before enabling the stricter bounds
checking. For example:
ptr = kmalloc_flex(*ptr, flex_member, count, gfp);
fill(ptr->flex, count);
ptr->flex_count = count;
This works correctly before adding a __counted_by annotation (since
nothing is checking ptr->flex accesses against ptr->flex_count). After
adding the annotation, the bounds sanitizer would trip during fill()
because ptr->flex_count wasn't set yet. But with kmalloc_flex() setting
ptr->flex_count internally at allocation time, the existing code works
without needing to move the ptr->flex_count assignment before the call
to fill(). (This has been a stumbling block for __counted_by adoption.)
Link: https://patch.msgid.link/20251203233036.3212363-4-kees@kernel.org
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Kees Cook <kees@kernel.org>
2025-12-03 15:30:34 -08:00
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2026-06-11 08:43:12 +02:00
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slab: Introduce kmalloc_obj() and family
Introduce type-aware kmalloc-family helpers to replace the common
idioms for single object and arrays of objects allocation:
ptr = kmalloc(sizeof(*ptr), gfp);
ptr = kmalloc(sizeof(struct some_obj_name), gfp);
ptr = kzalloc(sizeof(*ptr), gfp);
ptr = kmalloc_array(count, sizeof(*ptr), gfp);
ptr = kcalloc(count, sizeof(*ptr), gfp);
These become, respectively:
ptr = kmalloc_obj(*ptr, gfp);
ptr = kmalloc_obj(*ptr, gfp);
ptr = kzalloc_obj(*ptr, gfp);
ptr = kmalloc_objs(*ptr, count, gfp);
ptr = kzalloc_objs(*ptr, count, gfp);
Beyond the other benefits outlined below, the primary ergonomic benefit
is the elimination of needing "sizeof" nor the type name, and the
enforcement of assignment types (they do not return "void *", but rather
a pointer to the type of the first argument). The type name _can_ be
used, though, in the case where an assignment is indirect (e.g. via
"return"). This additionally allows[1] variables to be declared via
__auto_type:
__auto_type ptr = kmalloc_obj(struct foo, gfp);
Internal introspection of the allocated type now becomes possible,
allowing for future alignment-aware choices to be made by the allocator
and future hardening work that can be type sensitive. For example,
adding __alignof(*ptr) as an argument to the internal allocators so that
appropriate/efficient alignment choices can be made, or being able to
correctly choose per-allocation offset randomization within a bucket
that does not break alignment requirements.
Link: https://lore.kernel.org/all/CAHk-=wiCOTW5UftUrAnvJkr6769D29tF7Of79gUjdQHS_TkF5A@mail.gmail.com/ [1]
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://patch.msgid.link/20251203233036.3212363-1-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
2025-12-03 15:30:31 -08:00
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2026-04-29 09:27:04 +02:00
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slab: Introduce kmalloc_flex() and family
As done for kmalloc_obj*(), introduce a type-aware allocator for flexible
arrays, which may also have "counted_by" annotations:
ptr = kmalloc(struct_size(ptr, flex_member, count), gfp);
becomes:
ptr = kmalloc_flex(*ptr, flex_member, count, gfp);
The internal use of __flex_counter() allows for automatically setting
the counter member of a struct's flexible array member when it has
been annotated with __counted_by(), avoiding any missed early size
initializations while __counted_by() annotations are added to the
kernel. Additionally, this also checks for "too large" allocations based
on the type size of the counter variable. For example:
if (count > type_max(ptr->flex_counter))
fail...;
size = struct_size(ptr, flex_member, count);
ptr = kmalloc(size, gfp);
if (!ptr)
fail...;
ptr->flex_counter = count;
becomes (n.b. unchanged from earlier example):
ptr = kmalloc_flex(*ptr, flex_member, count, gfp);
if (!ptr)
fail...;
ptr->flex_counter = count;
Note that manual initialization of the flexible array counter is still
required (at some point) after allocation as not all compiler versions
support the __counted_by annotation yet. But doing it internally makes
sure they cannot be missed when __counted_by _is_ available, meaning
that the bounds checker will not trip due to the lack of "early enough"
initializations that used to work before enabling the stricter bounds
checking. For example:
ptr = kmalloc_flex(*ptr, flex_member, count, gfp);
fill(ptr->flex, count);
ptr->flex_count = count;
This works correctly before adding a __counted_by annotation (since
nothing is checking ptr->flex accesses against ptr->flex_count). After
adding the annotation, the bounds sanitizer would trip during fill()
because ptr->flex_count wasn't set yet. But with kmalloc_flex() setting
ptr->flex_count internally at allocation time, the existing code works
without needing to move the ptr->flex_count assignment before the call
to fill(). (This has been a stumbling block for __counted_by adoption.)
Link: https://patch.msgid.link/20251203233036.3212363-4-kees@kernel.org
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Kees Cook <kees@kernel.org>
2025-12-03 15:30:34 -08:00
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|
|
|
2026-04-29 09:27:04 +02:00
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|
slab: Introduce kmalloc_flex() and family
As done for kmalloc_obj*(), introduce a type-aware allocator for flexible
arrays, which may also have "counted_by" annotations:
ptr = kmalloc(struct_size(ptr, flex_member, count), gfp);
becomes:
ptr = kmalloc_flex(*ptr, flex_member, count, gfp);
The internal use of __flex_counter() allows for automatically setting
the counter member of a struct's flexible array member when it has
been annotated with __counted_by(), avoiding any missed early size
initializations while __counted_by() annotations are added to the
kernel. Additionally, this also checks for "too large" allocations based
on the type size of the counter variable. For example:
if (count > type_max(ptr->flex_counter))
fail...;
size = struct_size(ptr, flex_member, count);
ptr = kmalloc(size, gfp);
if (!ptr)
fail...;
ptr->flex_counter = count;
becomes (n.b. unchanged from earlier example):
ptr = kmalloc_flex(*ptr, flex_member, count, gfp);
if (!ptr)
fail...;
ptr->flex_counter = count;
Note that manual initialization of the flexible array counter is still
required (at some point) after allocation as not all compiler versions
support the __counted_by annotation yet. But doing it internally makes
sure they cannot be missed when __counted_by _is_ available, meaning
that the bounds checker will not trip due to the lack of "early enough"
initializations that used to work before enabling the stricter bounds
checking. For example:
ptr = kmalloc_flex(*ptr, flex_member, count, gfp);
fill(ptr->flex, count);
ptr->flex_count = count;
This works correctly before adding a __counted_by annotation (since
nothing is checking ptr->flex accesses against ptr->flex_count). After
adding the annotation, the bounds sanitizer would trip during fill()
because ptr->flex_count wasn't set yet. But with kmalloc_flex() setting
ptr->flex_count internally at allocation time, the existing code works
without needing to move the ptr->flex_count assignment before the call
to fill(). (This has been a stumbling block for __counted_by adoption.)
Link: https://patch.msgid.link/20251203233036.3212363-4-kees@kernel.org
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Kees Cook <kees@kernel.org>
2025-12-03 15:30:34 -08:00
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