Messages in this thread | ![/](/images/icornerl.gif) | | From | Linus Torvalds <> | Date | Tue, 24 Jan 2023 08:50:34 -0800 | Subject | Re: [PATCH AUTOSEL 6.1 35/35] ext4: deal with legacy signed xattr name hash values |
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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
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