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nfsd: ensure nfsd_file_do_acquire() does not use a non-opened file

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->atomic_open is permitted to return success without actually opening
the file.  It indicates this by calling finish_no_open().
This means dentry_create() can return a file which hasn't been opened.
This is extremely unlikely as ->atomic_open handlers typically
use finish_no_open() only for already existing files, and dentry_create()
isn't called in that case, and the parent being locked should prevent
races.

However out of an abundance of caution it seems wise to teach nfsd to
only use the file returned by dentry_create() if FMODE_OPENED is set,
indicating that it has in fact been opened.

Fixes: 64a989dbd1 ("VFS/knfsd: Teach dentry_create() to use atomic_open()")
Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown <neil@brown.name>
Link: https://patch.msgid.link/20260526053004.4014491-3-neilb@ownmail.net
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Benjamin Coddington <bcodding@hammerspace.com>
This commit is contained in:
NeilBrown
2026-05-26 15:27:59 +10:00
committed by Chuck Lever
parent 3e2c79360c
commit 5859cc01fe
1 changed files with 4 additions and 4 deletions
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8
fs/nfsd/filecache.c
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@@ -1227,7 +1227,7 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct net *net,
nf->nf_mark = nfsd_file_mark_find_or_create(inode);
if (type != S_IFREG || nf->nf_mark) {
if (file) {
if (file && (file->f_mode & FMODE_OPENED)) {
get_file(file);
nf->nf_file = file;
status = nfs_ok;
@@ -1374,12 +1374,12 @@ nfsd_file_acquire_local(struct net *net, struct svc_cred *cred,
* @rqstp: the RPC transaction being executed
* @fhp: the NFS filehandle of the file just created
* @may_flags: NFSD_MAY_ settings for the file
* @file: cached, already-open file (may be NULL)
* @file: cached, already-open file (may be NULL or not yet opened)
* @pnf: OUT: new or found "struct nfsd_file" object
*
* Acquire a nfsd_file object that is not GC'ed. If one doesn't already exist,
* and @file is non-NULL, use it to instantiate a new nfsd_file instead of
* opening a new one.
* and @file has FMODE_OPENED set, use it to instantiate a new nfsd_file
* instead of opening a new one.
*
* Return values:
* %nfs_ok - @pnf points to an nfsd_file with its reference