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nfs4_setup_readdir(): insufficient locking for ->d_parent->d_inode dereferencing

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Theoretically it's an oopsable race, but I don't believe one can manage
to hit it on real hardware; might become doable on a KVM, but it still
won't be easy to attack.

Anyway, it's easy to deal with - since xdr_encode_hyper() is just a call of
put_unaligned_be64(), we can put that under ->d_lock and be done with that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
This commit is contained in:
Al Viro
2025-09-16 17:22:45 +01:00
committed by Anna Schumaker
parent 902893e390
commit a890a2e339
1 changed files with 2 additions and 0 deletions
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2
fs/nfs/nfs4proc.c
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@@ -391,7 +391,9 @@ static void nfs4_setup_readdir(u64 cookie, __be32 *verifier, struct dentry *dent
*p++ = htonl(attrs); /* bitmap */
*p++ = htonl(12); /* attribute buffer length */
*p++ = htonl(NF4DIR);
spin_lock(&dentry->d_lock);
p = xdr_encode_hyper(p, NFS_FILEID(d_inode(dentry->d_parent)));
spin_unlock(&dentry->d_lock);
readdir->pgbase = (char *)p - (char *)start;
readdir->count -= readdir->pgbase;