[PATCH 4/4] smb: client: fix potential UAF in cifs_stats_proc_write()

[Chanho Min]

From: Paulo Alcantara <pc@xxxxxxxxxxxxx>

commit d3da25c5ac84430f89875ca7485a3828150a7e0a upstream.

Skip sessions that are being teared down (status == SES_EXITING) to
avoid UAF.

Cc: stable@xxxxxxxxxxxxxxx # 5.4
Signed-off-by: Paulo Alcantara (Red Hat) <pc@xxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
[ chanho: Backported to v5.4.y, cifs_debug.c was moved from fs/cifs to fs/smb/client ]
Signed-off-by: Chanho Min <chanho.min@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 fs/cifs/cifs_debug.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index df3dfa611c352..47190e676aa25 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -470,6 +470,8 @@ static ssize_t cifs_stats_proc_write(struct file *file,
 			}
 #endif /* CONFIG_CIFS_STATS2 */
 			list_for_each(tmp2, &server->smb_ses_list) {
+				if (cifs_ses_exiting(ses))
+					continue;
 				ses = list_entry(tmp2, struct cifs_ses,
 						 smb_ses_list);
 				list_for_each(tmp3, &ses->tcon_list) {