Patch "bcache: Silence memcpy() run-time false positive warnings" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    bcache: Silence memcpy() run-time false positive warnings

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bcache-silence-memcpy-run-time-false-positive-warnin.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 2caec17ccc2ec59bc4be9d1b298a5ff24e8a4f75
Author: Kees Cook <keescook@xxxxxxxxxxxx>
Date:   Thu Jan 5 22:02:33 2023 -0800

    bcache: Silence memcpy() run-time false positive warnings
    
    [ Upstream commit be0d8f48ad97f5b775b0af3310343f676dbf318a ]
    
    struct bkey has internal padding in a union, but it isn't always named
    the same (e.g. key ## _pad, key_p, etc). This makes it extremely hard
    for the compiler to reason about the available size of copies done
    against such keys. Use unsafe_memcpy() for now, to silence the many
    run-time false positive warnings:
    
      memcpy: detected field-spanning write (size 264) of single field "&i->j" at drivers/md/bcache/journal.c:152 (size 240)
      memcpy: detected field-spanning write (size 24) of single field "&b->key" at drivers/md/bcache/btree.c:939 (size 16)
      memcpy: detected field-spanning write (size 24) of single field "&temp.key" at drivers/md/bcache/extents.c:428 (size 16)
    
    Reported-by: Alexandre Pereira <alexpereira@xxxxxxxxxxx>
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=216785
    Acked-by: Coly Li <colyli@xxxxxxx>
    Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx>
    Cc: linux-bcache@xxxxxxxxxxxxxxx
    Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230106060229.never.047-kees@xxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/md/bcache/bcache_ondisk.h b/drivers/md/bcache/bcache_ondisk.h
index 97413586195b..f96034e0ba4f 100644
--- a/drivers/md/bcache/bcache_ondisk.h
+++ b/drivers/md/bcache/bcache_ondisk.h
@@ -106,7 +106,8 @@ static inline unsigned long bkey_bytes(const struct bkey *k)
 	return bkey_u64s(k) * sizeof(__u64);
 }
 
-#define bkey_copy(_dest, _src)	memcpy(_dest, _src, bkey_bytes(_src))
+#define bkey_copy(_dest, _src)	unsafe_memcpy(_dest, _src, bkey_bytes(_src), \
+					/* bkey is always padded */)
 
 static inline void bkey_copy_key(struct bkey *dest, const struct bkey *src)
 {
diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index e5da469a4235..c182c21de2e8 100644
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -149,7 +149,8 @@ reread:		left = ca->sb.bucket_size - offset;
 				    bytes, GFP_KERNEL);
 			if (!i)
 				return -ENOMEM;
-			memcpy(&i->j, j, bytes);
+			unsafe_memcpy(&i->j, j, bytes,
+				/* "bytes" was calculated by set_bytes() above */);
 			/* Add to the location after 'where' points to */
 			list_add(&i->list, where);
 			ret = 1;