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smfrenchgregkh
smfrench
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gregkh
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cifs: fix potential oops in cifs_oplock_break
[ Upstream commit e8f5f84 ] With deferred close we can have closes that race with lease breaks, and so with the current checks for whether to send the lease response, oplock_response(), this can mean that an unmount (kill_sb) can occur just before we were checking if the tcon->ses is valid. See below: [Fri Aug 4 04:12:50 2023] RIP: 0010:cifs_oplock_break+0x1f7/0x5b0 [cifs] [Fri Aug 4 04:12:50 2023] Code: 7d a8 48 8b 7d c0 c0 e9 02 48 89 45 b8 41 89 cf e8 3e f5 ff ff 4c 89 f7 41 83 e7 01 e8 82 b3 03 f2 49 8b 45 50 48 85 c0 74 5e <48> 83 78 60 00 74 57 45 84 ff 75 52 48 8b 43 98 48 83 eb 68 48 39 [Fri Aug 4 04:12:50 2023] RSP: 0018:ffffb30607ddbdf8 EFLAGS: 00010206 [Fri Aug 4 04:12:50 2023] RAX: 632d223d32612022 RBX: ffff97136944b1e0 RCX: 0000000080100009 [Fri Aug 4 04:12:50 2023] RDX: 0000000000000001 RSI: 0000000080100009 RDI: ffff97136944b188 [Fri Aug 4 04:12:50 2023] RBP: ffffb30607ddbe58 R08: 0000000000000001 R09: ffffffffc08e0900 [Fri Aug 4 04:12:50 2023] R10: 0000000000000001 R11: 000000000000000f R12: ffff97136944b138 [Fri Aug 4 04:12:50 2023] R13: ffff97149147c000 R14: ffff97136944b188 R15: 0000000000000000 [Fri Aug 4 04:12:50 2023] FS: 0000000000000000(0000) GS:ffff9714f7c00000(0000) knlGS:0000000000000000 [Fri Aug 4 04:12:50 2023] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [Fri Aug 4 04:12:50 2023] CR2: 00007fd8de9c7590 CR3: 000000011228e000 CR4: 0000000000350ef0 [Fri Aug 4 04:12:50 2023] Call Trace: [Fri Aug 4 04:12:50 2023] <TASK> [Fri Aug 4 04:12:50 2023] process_one_work+0x225/0x3d0 [Fri Aug 4 04:12:50 2023] worker_thread+0x4d/0x3e0 [Fri Aug 4 04:12:50 2023] ? process_one_work+0x3d0/0x3d0 [Fri Aug 4 04:12:50 2023] kthread+0x12a/0x150 [Fri Aug 4 04:12:50 2023] ? set_kthread_struct+0x50/0x50 [Fri Aug 4 04:12:50 2023] ret_from_fork+0x22/0x30 [Fri Aug 4 04:12:50 2023] </TASK> To fix this change the ordering of the checks before sending the oplock_response to first check if the openFileList is empty. Fixes: da787d5 ("SMB3: Do not send lease break acknowledgment if all file handles have been closed") Suggested-by: Bharath SM <bharathsm@microsoft.com> Reviewed-by: Bharath SM <bharathsm@microsoft.com> Reviewed-by: Shyam Prasad N <sprasad@microsoft.com> Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com> Signed-off-by: Steve French <stfrench@microsoft.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
1 parent a5ae5a8 commit b99f490

1 file changed

Lines changed: 16 additions & 7 deletions

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‎fs/cifs/file.c‎

Lines changed: 16 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -4865,9 +4865,11 @@ void cifs_oplock_break(struct work_struct *work)
48654865
struct cifsFileInfo *cfile = container_of(work, struct cifsFileInfo,
48664866
oplock_break);
48674867
struct inode *inode = d_inode(cfile->dentry);
4868+
struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
48684869
struct cifsInodeInfo *cinode = CIFS_I(inode);
4869-
struct cifs_tcon *tcon = tlink_tcon(cfile->tlink);
4870-
struct TCP_Server_Info *server = tcon->ses->server;
4870+
struct cifs_tcon *tcon;
4871+
struct TCP_Server_Info *server;
4872+
struct tcon_link *tlink;
48714873
int rc = 0;
48724874
bool purge_cache = false, oplock_break_cancelled;
48734875
__u64 persistent_fid, volatile_fid;
@@ -4876,6 +4878,12 @@ void cifs_oplock_break(struct work_struct *work)
48764878
wait_on_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS,
48774879
TASK_UNINTERRUPTIBLE);
48784880

4881+
tlink = cifs_sb_tlink(cifs_sb);
4882+
if (IS_ERR(tlink))
4883+
goto out;
4884+
tcon = tlink_tcon(tlink);
4885+
server = tcon->ses->server;
4886+
48794887
server->ops->downgrade_oplock(server, cinode, cfile->oplock_level,
48804888
cfile->oplock_epoch, &purge_cache);
48814889

@@ -4925,18 +4933,19 @@ void cifs_oplock_break(struct work_struct *work)
49254933
/*
49264934
* MS-SMB2 3.2.5.19.1 and 3.2.5.19.2 (and MS-CIFS 3.2.5.42) do not require
49274935
* an acknowledgment to be sent when the file has already been closed.
4928-
* check for server null, since can race with kill_sb calling tree disconnect.
49294936
*/
49304937
spin_lock(&cinode->open_file_lock);
4931-
if (tcon->ses && tcon->ses->server && !oplock_break_cancelled &&
4932-
!list_empty(&cinode->openFileList)) {
4938+
/* check list empty since can race with kill_sb calling tree disconnect */
4939+
if (!oplock_break_cancelled && !list_empty(&cinode->openFileList)) {
49334940
spin_unlock(&cinode->open_file_lock);
4934-
rc = tcon->ses->server->ops->oplock_response(tcon, persistent_fid,
4935-
volatile_fid, net_fid, cinode);
4941+
rc = server->ops->oplock_response(tcon, persistent_fid,
4942+
volatile_fid, net_fid, cinode);
49364943
cifs_dbg(FYI, "Oplock release rc = %d\n", rc);
49374944
} else
49384945
spin_unlock(&cinode->open_file_lock);
49394946

4947+
cifs_put_tlink(tlink);
4948+
out:
49404949
cifs_done_oplock_break(cinode);
49414950
}
49424951

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