linux-kernel - [PATCH v2] cifs: avoid possible NULL dereference

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Date:   Tue, 26 Sep 2023 09:27:34 +0800
From:   Su Hui <suhui@...china.com>
To:     sfrench@...ba.org, pc@...guebit.com, lsahlber@...hat.com,
        sprasad@...rosoft.com, tom@...pey.com
Cc:     Su Hui <suhui@...china.com>, dan.carpenter@...aro.org,
        linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH v2] cifs: avoid possible NULL dereference

smatch warn:
fs/smb/client/file.c:4910 cifs_oplock_break() warn:
variable dereferenced before check 'inode' (see line 4881)

If 'inode' is NULL, print some warning and return.

Signed-off-by: Su Hui <suhui@...china.com>
---
 fs/smb/client/file.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/fs/smb/client/file.c b/fs/smb/client/file.c
index 2108b3b40ce9..de705c8b2d22 100644
--- a/fs/smb/client/file.c
+++ b/fs/smb/client/file.c
@@ -4878,8 +4878,8 @@ void cifs_oplock_break(struct work_struct *work)
 	struct cifsFileInfo *cfile = container_of(work, struct cifsFileInfo,
 						  oplock_break);
 	struct inode *inode = d_inode(cfile->dentry);
-	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
-	struct cifsInodeInfo *cinode = CIFS_I(inode);
+	struct cifs_sb_info *cifs_sb;
+	struct cifsInodeInfo *cinode;
 	struct cifs_tcon *tcon;
 	struct TCP_Server_Info *server;
 	struct tcon_link *tlink;
@@ -4888,6 +4888,13 @@ void cifs_oplock_break(struct work_struct *work)
 	__u64 persistent_fid, volatile_fid;
 	__u16 net_fid;
 
+	if (!inode) {
+		cifs_dbg(FYI, "%s : failed to find inode\n", __func__);
+		return;
+	}
+	cifs_sb = CIFS_SB(inode->i_sb);
+	cinode = CIFS_I(inode);
+
 	wait_on_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS,
 			TASK_UNINTERRUPTIBLE);
 
@@ -4907,7 +4914,7 @@ void cifs_oplock_break(struct work_struct *work)
 		cinode->oplock = 0;
 	}
 
-	if (inode && S_ISREG(inode->i_mode)) {
+	if (S_ISREG(inode->i_mode)) {
 		if (CIFS_CACHE_READ(cinode))
 			break_lease(inode, O_RDONLY);
 		else
-- 
2.30.2