bcachefs: Refactor memcpy into direct assignment
The memcpy() in bch2_bkey_append_ptr() is operating on an embedded fake flexible array which looks to the compiler like it has 0 size. This causes W=1 builds to emit warnings due to -Wstringop-overflow: In file included from include/linux/string.h:254, from include/linux/bitmap.h:11, from include/linux/cpumask.h:12, from include/linux/smp.h:13, from include/linux/lockdep.h:14, from include/linux/radix-tree.h:14, from include/linux/backing-dev-defs.h:6, from fs/bcachefs/bcachefs.h:182: fs/bcachefs/extents.c: In function 'bch2_bkey_append_ptr': include/linux/fortify-string.h:57:33: warning: writing 8 bytes into a region of size 0 [-Wstringop-overflow=] 57 | #define __underlying_memcpy __builtin_memcpy | ^ include/linux/fortify-string.h:648:9: note: in expansion of macro '__underlying_memcpy' 648 | __underlying_##op(p, q, __fortify_size); \ | ^~~~~~~~~~~~~ include/linux/fortify-string.h:693:26: note: in expansion of macro '__fortify_memcpy_chk' 693 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ | ^~~~~~~~~~~~~~~~~~~~ fs/bcachefs/extents.c:235:17: note: in expansion of macro 'memcpy' 235 | memcpy((void *) &k->v + bkey_val_bytes(&k->k), | ^~~~~~ fs/bcachefs/bcachefs_format.h:287:33: note: destination object 'v' of size 0 287 | struct bch_val v; | ^ Avoid making any structure changes and just replace the u64 copy into a direct assignment, side-stepping the entire problem. Cc: Kent Overstreet <kent.overstreet@linux.dev> Cc: Brian Foster <bfoster@redhat.com> Cc: linux-bcachefs@vger.kernel.org Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202309192314.VBsjiIm5-lkp@intel.com/ Link: https://lore.kernel.org/r/20231010235609.work.594-kees@kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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1 changed files with 4 additions and 6 deletions
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@ -633,6 +633,8 @@ void bch2_bkey_extent_entry_drop(struct bkey_i *, union bch_extent_entry *);
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static inline void bch2_bkey_append_ptr(struct bkey_i *k, struct bch_extent_ptr ptr)
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{
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struct bch_extent_ptr *dest;
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EBUG_ON(bch2_bkey_has_device(bkey_i_to_s(k), ptr.dev));
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switch (k->k.type) {
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@ -642,12 +644,8 @@ static inline void bch2_bkey_append_ptr(struct bkey_i *k, struct bch_extent_ptr
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EBUG_ON(bkey_val_u64s(&k->k) >= BKEY_EXTENT_VAL_U64s_MAX);
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ptr.type = 1 << BCH_EXTENT_ENTRY_ptr;
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unsafe_memcpy((void *) &k->v + bkey_val_bytes(&k->k),
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&ptr,
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sizeof(ptr),
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"Our memcpy target is relative to a zero size array ,"
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"compiler bounds checking doesn't work here");
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dest = (struct bch_extent_ptr *)((void *) &k->v + bkey_val_bytes(&k->k));
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*dest = ptr;
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k->k.u64s++;
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break;
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default:
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