On Thu, Feb 06, 2025 at 03:59:53PM -0800, Suren Baghdasaryan wrote: > 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()")
Yeah, that should be dropped. I intend to send this fix series to Linus tomorrow or Saturday before rc2. -Kees > > > --- > > 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 > > -- Kees Cook
