On Thu, Feb 6, 2025 at 1:40 PM Kees Cook <[email protected]> wrote: > > The destination argument of memtostr*() and strtomem*() must be a > fixed-size char array at compile time, so there is no need to use > __builtin_object_size() (which is useful for when an argument is > either a pointer or unknown). Instead use ARRAY_SIZE(), which has the > benefit of working around a bug in Clang (fixed[1] in 15+) that got > __builtin_object_size() wrong sometimes. > > Reported-by: kernel test robot <[email protected]> > Closes: > https://lore.kernel.org/oe-kbuild-all/[email protected]/ > Suggested-by: Kent Overstreet <[email protected]> > Link: > https://github.com/llvm/llvm-project/commit/d8e0a6d5e9dd2311641f9a8a5d2bf90829951ddc > [1] > Signed-off-by: Kees Cook <[email protected]>
Tested-by: Suren Baghdasaryan <[email protected]> Thanks Kees! CC'ing Andrew Morton since mm-unstable contains my workaround patch [1] for the issue fixed by this patchset. I'm not sure which tree will be taking these fixes but once they are in we should drop [1]. Or maybe we just drop it now from mm-unstable? Seems like only testbot was the only one who complained... [1] 0e91345e75b2 ("alloc_tag: work around clang-14 build issue with __builtin_object_size()") > --- > Cc: Suren Baghdasaryan <[email protected]> > Cc: [email protected] > Cc: Andy Shevchenko <[email protected]> > Cc: [email protected] > --- > include/linux/string.h | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/include/linux/string.h b/include/linux/string.h > index 493ac4862c77..fc5ae145bd78 100644 > --- a/include/linux/string.h > +++ b/include/linux/string.h > @@ -411,7 +411,8 @@ void memcpy_and_pad(void *dest, size_t dest_len, const > void *src, size_t count, > * must be discoverable by the compiler. > */ > #define strtomem_pad(dest, src, pad) do { \ > - const size_t _dest_len = __builtin_object_size(dest, 1); \ > + const size_t _dest_len = __must_be_byte_array(dest) + \ > + ARRAY_SIZE(dest); \ > const size_t _src_len = __builtin_object_size(src, 1); \ > \ > BUILD_BUG_ON(!__builtin_constant_p(_dest_len) || \ > @@ -434,7 +435,8 @@ void memcpy_and_pad(void *dest, size_t dest_len, const > void *src, size_t count, > * must be discoverable by the compiler. > */ > #define strtomem(dest, src) do { \ > - const size_t _dest_len = __builtin_object_size(dest, 1); \ > + const size_t _dest_len = __must_be_byte_array(dest) + \ > + ARRAY_SIZE(dest); \ > const size_t _src_len = __builtin_object_size(src, 1); \ > \ > BUILD_BUG_ON(!__builtin_constant_p(_dest_len) || \ > @@ -453,7 +455,8 @@ void memcpy_and_pad(void *dest, size_t dest_len, const > void *src, size_t count, > * Note that sizes of @dest and @src must be known at compile-time. > */ > #define memtostr(dest, src) do { \ > - const size_t _dest_len = __builtin_object_size(dest, 1); \ > + const size_t _dest_len = __must_be_byte_array(dest) + \ > + ARRAY_SIZE(dest); \ > const size_t _src_len = __builtin_object_size(src, 1); \ > const size_t _src_chars = strnlen(src, _src_len); \ > const size_t _copy_len = min(_dest_len - 1, _src_chars); \ > @@ -478,7 +481,8 @@ void memcpy_and_pad(void *dest, size_t dest_len, const > void *src, size_t count, > * Note that sizes of @dest and @src must be known at compile-time. > */ > #define memtostr_pad(dest, src) do { > \ > - const size_t _dest_len = __builtin_object_size(dest, 1); \ > + const size_t _dest_len = __must_be_byte_array(dest) + \ > + ARRAY_SIZE(dest); \ > const size_t _src_len = __builtin_object_size(src, 1); \ > const size_t _src_chars = strnlen(src, _src_len); \ > const size_t _copy_len = min(_dest_len - 1, _src_chars); \ > -- > 2.34.1 >
