On Tue, Jan 24, 2023 at 5:42 AM Sasha Levin sashal@kernel.org wrote:
From: Linus Torvalds torvalds@linux-foundation.org
[ Upstream commit f3bbac32475b27f49be201f896d98d4009de1562 ]
We potentially have old hashes of the xattr names generated on systems with signed 'char' types. Now that everybody uses '-funsigned-char', those hashes will no longer match.
This patch does not work correctly without '-funsigned-char', and I don't think that has been back-ported to stable kernels.
That said, the patch *almost* works. You'd just have to add something like this to it:
--- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -3096,7 +3096,7 @@ static __le32 ext4_xattr_hash_entry(char *name, while (name_len--) { hash = (hash << NAME_HASH_SHIFT) ^ (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^ - *name++; + (unsigned char)*name++; } while (value_count--) { hash = (hash << VALUE_HASH_SHIFT) ^
to make it work right (ie just make sure that the proper xattr name hashing actually uses unsigned chars for its hash).
Linus