diff options
| author | Winston Wen <wentao@uniontech.com> | 2023-06-26 06:42:55 +0300 |
|---|---|---|
| committer | Steve French <stfrench@microsoft.com> | 2023-07-01 08:08:59 +0300 |
| commit | ff7d80a9f2711bf3d9fe1cfb70b3fd15c50584b7 (patch) | |
| tree | 43ccd8a78020d79f51d3bc1d9f0bc3953a64a75c /fs/smb | |
| parent | a507db1d8fdc39802415e4d2ef6d1aecd67927fa (diff) | |
| download | linux-ff7d80a9f2711bf3d9fe1cfb70b3fd15c50584b7.tar.xz | |
cifs: fix session state transition to avoid use-after-free issue
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@uniontech.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs/smb')
| -rw-r--r-- | fs/smb/client/connect.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/fs/smb/client/connect.c b/fs/smb/client/connect.c index dab7bc876507..85dd1b373974 100644 --- a/fs/smb/client/connect.c +++ b/fs/smb/client/connect.c @@ -1967,15 +1967,16 @@ 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); |