From: Winston Wen <wentao@xxxxxxxxxxxxx>
[ Upstream commit ff7d80a9f2711bf3d9fe1cfb70b3fd15c50584b7 ]
We switch session state to SES_EXITING without cifs_tcp_ses_lock now,
it may lead to potential use-after-free issue.
Consider the following execution processes:
Thread 1:
__cifs_put_smb_ses()
spin_lock(&cifs_tcp_ses_lock)
if (--ses->ses_count > 0)
spin_unlock(&cifs_tcp_ses_lock)
return
spin_unlock(&cifs_tcp_ses_lock)
---> **GAP**
spin_lock(&ses->ses_lock)
if (ses->ses_status == SES_GOOD)
ses->ses_status = SES_EXITING
spin_unlock(&ses->ses_lock)
Thread 2:
cifs_find_smb_ses()
spin_lock(&cifs_tcp_ses_lock)
list_for_each_entry(ses, ...)
spin_lock(&ses->ses_lock)
if (ses->ses_status == SES_EXITING)
spin_unlock(&ses->ses_lock)
continue
...
spin_unlock(&ses->ses_lock)
if (ret)
cifs_smb_ses_inc_refcount(ret)
spin_unlock(&cifs_tcp_ses_lock)
If thread 1 is preempted in the gap and thread 2 start executing, thread 2
will get the session, and soon thread 1 will switch the session state to
SES_EXITING and start releasing it, even though thread 1 had increased the
session's refcount and still uses it.
So switch session state under cifs_tcp_ses_lock to eliminate this gap.
Signed-off-by: Winston Wen <wentao@xxxxxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/smb/client/connect.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c
index 9d16626e7a669..165ecb222c19b 100644
--- a/fs/smb/client/connect.c
+++ b/fs/smb/client/connect.c
@@ -1963,15 +1963,16 @@ void __cifs_put_smb_ses(struct cifs_ses *ses)
spin_unlock(&cifs_tcp_ses_lock);
return;
}
+ spin_lock(&ses->ses_lock);
+ if (ses->ses_status == SES_GOOD)
+ ses->ses_status = SES_EXITING;
+ spin_unlock(&ses->ses_lock);
spin_unlock(&cifs_tcp_ses_lock);
/* ses_count can never go negative */
WARN_ON(ses->ses_count < 0);
spin_lock(&ses->ses_lock);
- if (ses->ses_status == SES_GOOD)
- ses->ses_status = SES_EXITING;
-
if (ses->ses_status == SES_EXITING && server->ops->logoff) {
spin_unlock(&ses->ses_lock);
cifs_free_ipc(ses);
--
2.40.1
