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lockd: Avoid hashing uninitialized bytes in nlm4svc_lookup_file()

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file_hash() digests the first LOCKD_FH_HASH_SIZE bytes of
nfs_fh.data when bucketing nlm_files[], independent of fh.size.
Commit 3de744ee4e ("lockd: Use xdrgen XDR functions for the
NLMv4 TEST procedure") set .pc_argzero to zero for the converted
procedures and moved file-handle population into
nlm4svc_lookup_file(), which copies only xdr_lock->fh.len bytes
into lock->fh.data.

When an NLMv4 client presents a file handle shorter than
LOCKD_FH_HASH_SIZE, bytes fh.len..31 retain whatever the argument
buffer held from an earlier request.  The same wire handle then
hashes to different buckets across calls; nlm_lookup_file() misses
the existing nlm_file entry, and lock-state lookups fail.

Zero only the tail bytes that file_hash() would otherwise consume.
Handles of LOCKD_FH_HASH_SIZE or larger already populate every byte
that file_hash() reads.

Reported-by: Jeff Layton <jlayton@kernel.org>
Closes: https://lore.kernel.org/r/5229a9746d723a3f830120c0b966510f75badfc2.camel@kernel.org
Fixes: 3de744ee4e ("lockd: Use xdrgen XDR functions for the NLMv4 TEST procedure")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Chuck Lever 2026-05-14 16:56:07 -04:00 committed by Chuck Lever
parent 70a38f87be
commit 6e4c62caec
3 changed files with 12 additions and 2 deletions
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8
fs/lockd/lockd.h
View File

@ -52,6 +52,14 @@
*/
#define LOCKD_DFLT_TIMEO 10
/*
* Number of leading bytes of nfs_fh.data that file_hash()
* digests when bucketing nlm_files[]. Sized for historical
* NFSv2 handles; nfs_fh.data must be initialized at least
* this far before lookup, regardless of fh.size.
*/
#define LOCKD_FH_HASH_SIZE 32
/* error codes new to NLMv4 */
#define nlm4_deadlock cpu_to_be32(NLM_DEADLCK)
#define nlm4_rofs cpu_to_be32(NLM_ROFS)

3
fs/lockd/svc4proc.c
View File

@ -156,6 +156,9 @@ nlm4svc_lookup_file(struct svc_rqst *rqstp, struct nlm_host *host,
return nlm_lck_denied_nolocks;
lock->fh.size = xdr_lock->fh.len;
memcpy(lock->fh.data, xdr_lock->fh.data, xdr_lock->fh.len);
if (xdr_lock->fh.len < LOCKD_FH_HASH_SIZE)
memset(lock->fh.data + xdr_lock->fh.len, 0,
LOCKD_FH_HASH_SIZE - xdr_lock->fh.len);
lock->oh.len = xdr_lock->oh.len;
lock->oh.data = xdr_lock->oh.data;

3
fs/lockd/svcsubs.c
View File

@ -17,7 +17,6 @@
#include <linux/sunrpc/addr.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <uapi/linux/nfs2.h>
#include "lockd.h"
#include "share.h"
@ -67,7 +66,7 @@ static inline unsigned int file_hash(struct nfs_fh *f)
{
unsigned int tmp=0;
int i;
for (i=0; i<NFS2_FHSIZE;i++)
for (i = 0; i < LOCKD_FH_HASH_SIZE; i++)
tmp += f->data[i];
return tmp & (FILE_NRHASH - 1);
}