From: Kees Cook keescook@chromium.org
[ Upstream commit 86cffecdeaa278444870c8745ab166a65865dbf0 ]
GCC and Clang can use the "alloc_size" attribute to better inform the results of __builtin_object_size() (for compile-time constant values). Clang can additionally use alloc_size to inform the results of __builtin_dynamic_object_size() (for run-time values).
Because GCC sees the frequent use of struct_size() as an allocator size argument, and notices it can return SIZE_MAX (the overflow indication), it complains about these call sites overflowing (since SIZE_MAX is greater than the default -Walloc-size-larger-than=PTRDIFF_MAX). This isn't helpful since we already know a SIZE_MAX will be caught at run-time (this was an intentional design). To deal with this, we must disable this check as it is both a false positive and redundant. (Clang does not have this warning option.)
Unfortunately, just checking the -Wno-alloc-size-larger-than is not sufficient to make the __alloc_size attribute behave correctly under older GCC versions. The attribute itself must be disabled in those situations too, as there appears to be no way to reliably silence the SIZE_MAX constant expression cases for GCC versions less than 9.1:
In file included from ./include/linux/resource_ext.h:11, from ./include/linux/pci.h:40, from drivers/net/ethernet/intel/ixgbe/ixgbe.h:9, from drivers/net/ethernet/intel/ixgbe/ixgbe_lib.c:4: In function 'kmalloc_node', inlined from 'ixgbe_alloc_q_vector' at ./include/linux/slab.h:743:9: ./include/linux/slab.h:618:9: error: argument 1 value '18446744073709551615' exceeds maximum object size 9223372036854775807 [-Werror=alloc-size-larger-than=] return __kmalloc_node(size, flags, node); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ./include/linux/slab.h: In function 'ixgbe_alloc_q_vector': ./include/linux/slab.h:455:7: note: in a call to allocation function '__kmalloc_node' declared here void *__kmalloc_node(size_t size, gfp_t flags, int node) __assume_slab_alignment __malloc; ^~~~~~~~~~~~~~
Specifically: '-Wno-alloc-size-larger-than' is not correctly handled by GCC < 9.1 https://godbolt.org/z/hqsfG7q84 (doesn't disable) https://godbolt.org/z/P9jdrPTYh (doesn't admit to not knowing about option) https://godbolt.org/z/465TPMWKb (only warns when other warnings appear)
'-Walloc-size-larger-than=18446744073709551615' is not handled by GCC < 8.2 https://godbolt.org/z/73hh1EPxz (ignores numeric value)
Since anything marked with __alloc_size would also qualify for marking with __malloc, just include __malloc along with it to avoid redundant markings. (Suggested by Linus Torvalds.)
Finally, make sure checkpatch.pl doesn't get confused about finding the __alloc_size attribute on functions. (Thanks to Joe Perches.)
Link: https://lkml.kernel.org/r/20210930222704.2631604-3-keescook@chromium.org Signed-off-by: Kees Cook keescook@chromium.org Tested-by: Randy Dunlap rdunlap@infradead.org Cc: Andy Whitcroft apw@canonical.com Cc: Christoph Lameter cl@linux.com Cc: Daniel Micay danielmicay@gmail.com Cc: David Rientjes rientjes@google.com Cc: Dennis Zhou dennis@kernel.org Cc: Dwaipayan Ray dwaipayanray1@gmail.com Cc: Joe Perches joe@perches.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Lukas Bulwahn lukas.bulwahn@gmail.com Cc: Pekka Enberg penberg@kernel.org Cc: Tejun Heo tj@kernel.org Cc: Vlastimil Babka vbabka@suse.cz Cc: Alexandre Bounine alex.bou9@gmail.com Cc: Gustavo A. R. Silva gustavoars@kernel.org Cc: Ira Weiny ira.weiny@intel.com Cc: Jing Xiangfeng jingxiangfeng@huawei.com Cc: John Hubbard jhubbard@nvidia.com Cc: kernel test robot lkp@intel.com Cc: Matt Porter mporter@kernel.crashing.org Cc: Miguel Ojeda ojeda@kernel.org Cc: Nathan Chancellor nathan@kernel.org Cc: Nick Desaulniers ndesaulniers@google.com Cc: Souptick Joarder jrdr.linux@gmail.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- Makefile | 15 +++++++++++++++ include/linux/compiler-gcc.h | 8 ++++++++ include/linux/compiler_attributes.h | 10 ++++++++++ include/linux/compiler_types.h | 12 ++++++++++++ scripts/checkpatch.pl | 3 ++- 5 files changed, 47 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile index c7750d260a55..397fb08d17f2 100644 --- a/Makefile +++ b/Makefile @@ -1011,6 +1011,21 @@ ifdef CONFIG_CC_IS_GCC KBUILD_CFLAGS += -Wno-maybe-uninitialized endif
+ifdef CONFIG_CC_IS_GCC +# The allocators already balk at large sizes, so silence the compiler +# warnings for bounds checks involving those possible values. While +# -Wno-alloc-size-larger-than would normally be used here, earlier versions +# of gcc (<9.1) weirdly don't handle the option correctly when _other_ +# warnings are produced (?!). Using -Walloc-size-larger-than=SIZE_MAX +# doesn't work (as it is documented to), silently resolving to "0" prior to +# version 9.1 (and producing an error more recently). Numeric values larger +# than PTRDIFF_MAX also don't work prior to version 9.1, which are silently +# ignored, continuing to default to PTRDIFF_MAX. So, left with no other +# choice, we must perform a versioned check to disable this warning. +# https://lore.kernel.org/lkml/20210824115859.187f272f@canb.auug.org.au +KBUILD_CFLAGS += $(call cc-ifversion, -ge, 0901, -Wno-alloc-size-larger-than) +endif + # disable invalid "can't wrap" optimizations for signed / pointers KBUILD_CFLAGS += -fno-strict-overflow
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index bd2b881c6b63..b9d5f9c373a0 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -144,3 +144,11 @@ #else #define __diag_GCC_8(s) #endif + +/* + * Prior to 9.1, -Wno-alloc-size-larger-than (and therefore the "alloc_size" + * attribute) do not work, and must be disabled. + */ +#if GCC_VERSION < 90100 +#undef __alloc_size__ +#endif diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h index e6ec63403965..3de06a8fae73 100644 --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -33,6 +33,15 @@ #define __aligned(x) __attribute__((__aligned__(x))) #define __aligned_largest __attribute__((__aligned__))
+/* + * Note: do not use this directly. Instead, use __alloc_size() since it is conditionally + * available and includes other attributes. + * + * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-all... + * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size + */ +#define __alloc_size__(x, ...) __attribute__((__alloc_size__(x, ## __VA_ARGS__))) + /* * Note: users of __always_inline currently do not write "inline" themselves, * which seems to be required by gcc to apply the attribute according @@ -153,6 +162,7 @@
/* * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-mal... + * clang: https://clang.llvm.org/docs/AttributeReference.html#malloc */ #define __malloc __attribute__((__malloc__))
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index b6ff83a714ca..4f2203c4a257 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -250,6 +250,18 @@ struct ftrace_likely_data { # define __cficanonical #endif
+/* + * Any place that could be marked with the "alloc_size" attribute is also + * a place to be marked with the "malloc" attribute. Do this as part of the + * __alloc_size macro to avoid redundant attributes and to avoid missing a + * __malloc marking. + */ +#ifdef __alloc_size__ +# define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc +#else +# define __alloc_size(x, ...) __malloc +#endif + #ifndef asm_volatile_goto #define asm_volatile_goto(x...) asm goto(x) #endif diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index c27d2312cfc3..88cb294dc447 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -489,7 +489,8 @@ our $Attribute = qr{ ____cacheline_aligned| ____cacheline_aligned_in_smp| ____cacheline_internodealigned_in_smp| - __weak + __weak| + __alloc_size\s*(\s*\d+\s*(?:,\s*\d+\s*)?) }x; our $Modifier; our $Inline = qr{inline|__always_inline|noinline|__inline|__inline__};