Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Subject: [PATCH v3 32/32] NFSD: Ensure nf_inode is never dereferenced
From:   Chuck Lever <chuck.lever@oracle.com>
To:     linux-nfs@vger.kernel.org, netdev@vger.kernel.org
Cc:     david@fromorbit.com, jlayton@redhat.com, tgraf@suug.ch
Date:   Fri, 08 Jul 2022 14:27:09 -0400
Message-ID: <165730482946.28142.13069318391976207471.stgit@klimt.1015granger.net>
In-Reply-To: <165730437087.28142.6731645688073512500.stgit@klimt.1015granger.net>
References: <165730437087.28142.6731645688073512500.stgit@klimt.1015granger.net>
User-Agent: StGit/1.5.dev3+g9561319
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Precedence: bulk

The documenting comment for struct nf_file states:

/*
 * A representation of a file that has been opened by knfsd. These are hashed
 * in the hashtable by inode pointer value. Note that this object doesn't
 * hold a reference to the inode by itself, so the nf_inode pointer should
 * never be dereferenced, only used for comparison.
 */

Replace the two existing dereferences to make the comment always
true.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/filecache.c |    5 ++---
 fs/nfsd/filecache.h |    2 +-
 fs/nfsd/nfs4state.c |    2 +-
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 36d61012d5de..11099c8918a4 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -228,12 +228,11 @@ nfsd_file_mark_put(struct nfsd_file_mark *nfm)
 }
 
 static struct nfsd_file_mark *
-nfsd_file_mark_find_or_create(struct nfsd_file *nf)
+nfsd_file_mark_find_or_create(struct nfsd_file *nf, struct inode *inode)
 {
 	int			err;
 	struct fsnotify_mark	*mark;
 	struct nfsd_file_mark	*nfm = NULL, *new;
-	struct inode *inode = nf->nf_inode;
 
 	do {
 		fsnotify_group_lock(nfsd_file_fsnotify_group);
@@ -1164,7 +1163,7 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
 
 open_file:
 	trace_nfsd_file_alloc(nf);
-	nf->nf_mark = nfsd_file_mark_find_or_create(nf);
+	nf->nf_mark = nfsd_file_mark_find_or_create(nf, key.inode);
 	if (nf->nf_mark) {
 		if (open) {
 			status = nfsd_open_verified(rqstp, fhp, may_flags,
diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h
index c5ddc877116b..d534b76cb65b 100644
--- a/fs/nfsd/filecache.h
+++ b/fs/nfsd/filecache.h
@@ -41,7 +41,7 @@ struct nfsd_file {
 #define NFSD_FILE_BREAK_WRITE	(3)
 #define NFSD_FILE_REFERENCED	(4)
 	unsigned long		nf_flags;
-	struct inode		*nf_inode;
+	struct inode		*nf_inode;	/* don't deref */
 	refcount_t		nf_ref;
 	unsigned char		nf_may;
 	struct nfsd_file_mark	*nf_mark;
diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 9d1a3e131c49..994bd11bafe0 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -2564,7 +2564,7 @@ static void nfs4_show_fname(struct seq_file *s, struct nfsd_file *f)
 
 static void nfs4_show_superblock(struct seq_file *s, struct nfsd_file *f)
 {
-	struct inode *inode = f->nf_inode;
+	struct inode *inode = file_inode(f->nf_file);
 
 	seq_printf(s, "superblock: \"%02x:%02x:%ld\"",
 					MAJOR(inode->i_sb->s_dev),