[PATCH 5.7 043/204] cifs: Fix leak when handling lease break for cached root fid

Greg Kroah-Hartman
2020-08-20T13:14:04Z

From: Paul Aurich <paul@darkrain42.org>

commit baf57b56d3604880ccb3956ec6c62ea894f5de99 upstream.

Handling a lease break for the cached root didn't free the
smb2_lease_break_work allocation, resulting in a leak:

unreferenced object 0xffff98383a5af480 (size 128):
comm "cifsd", pid 684, jiffies 4294936606 (age 534.868s)
hex dump (first 32 bytes):
c0 ff ff ff 1f 00 00 00 88 f4 5a 3a 38 98 ff ff ..........Z:8...
88 f4 5a 3a 38 98 ff ff 80 88 d6 8a ff ff ff ff ..Z:8...........
backtrace:
[<0000000068957336>] smb2_is_valid_oplock_break+0x1fa/0x8c0
[<0000000073b70b9e>] cifs_demultiplex_thread+0x73d/0xcc0
[<00000000905fa372>] kthread+0x11c/0x150
[<0000000079378e4e>] ret_from_fork+0x22/0x30

Avoid this leak by only allocating when necessary.

Fixes: a93864d93977 ("cifs: add lease tracking to the cached root fid")
Signed-off-by: Paul Aurich <paul@darkrain42.org>
CC: Stable <stable@vger.kernel.org> # v4.18+
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/cifs/smb2misc.c | 73 +++++++++++++++++++++++++++++++++++++----------------
1 file changed, 52 insertions(+), 21 deletions(-)

--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -508,15 +508,31 @@ cifs_ses_oplock_break(struct work_struct
kfree(lw);
}

+static void
+smb2_queue_pending_open_break(struct tcon_link *tlink, __u8 *lease_key,
+ __le32 new_lease_state)
+{
+ struct smb2_lease_break_work *lw;
+
+ lw = kmalloc(sizeof(struct smb2_lease_break_work), GFP_KERNEL);
+ if (!lw) {
+ cifs_put_tlink(tlink);
+ return;
+ }
+
+ INIT_WORK(&lw->lease_break, cifs_ses_oplock_break);
+ lw->tlink = tlink;
+ lw->lease_state = new_lease_state;
+ memcpy(lw->lease_key, lease_key, SMB2_LEASE_KEY_SIZE);
+ queue_work(cifsiod_wq, &lw->lease_break);
+}
+
static bool
-smb2_tcon_has_lease(struct cifs_tcon *tcon, struct smb2_lease_break *rsp,
- struct smb2_lease_break_work *lw)
+smb2_tcon_has_lease(struct cifs_tcon *tcon, struct smb2_lease_break *rsp)
{
- bool found;
__u8 lease_state;
struct list_head *tmp;
struct cifsFileInfo *cfile;
- struct cifs_pending_open *open;
struct cifsInodeInfo *cinode;
int ack_req = le32_to_cpu(rsp->Flags &
SMB2_NOTIFY_BREAK_LEASE_FLAG_ACK_REQUIRED);
@@ -546,22 +562,29 @@ smb2_tcon_has_lease(struct cifs_tcon *tc
cfile->oplock_level = lease_state;

cifs_queue_oplock_break(cfile);
- kfree(lw);
return true;
}

- found = false;
+ return false;
+}
+
+static struct cifs_pending_open *
+smb2_tcon_find_pending_open_lease(struct cifs_tcon *tcon,
+ struct smb2_lease_break *rsp)
+{
+ __u8 lease_state = le32_to_cpu(rsp->NewLeaseState);
+ int ack_req = le32_to_cpu(rsp->Flags &
+ SMB2_NOTIFY_BREAK_LEASE_FLAG_ACK_REQUIRED);
+ struct cifs_pending_open *open;
+ struct cifs_pending_open *found = NULL;
+
list_for_each_entry(open, &tcon->pending_opens, olist) {
if (memcmp(open->lease_key, rsp->LeaseKey,
SMB2_LEASE_KEY_SIZE))
continue;

if (!found && ack_req) {
- found = true;
- memcpy(lw->lease_key, open->lease_key,
- SMB2_LEASE_KEY_SIZE);
- lw->tlink = cifs_get_tlink(open->tlink);
- queue_work(cifsiod_wq, &lw->lease_break);
+ found = open;
}

cifs_dbg(FYI, "found in the pending open list\n");
@@ -582,14 +605,7 @@ smb2_is_valid_lease_break(char *buffer)
struct TCP_Server_Info *server;
struct cifs_ses *ses;
struct cifs_tcon *tcon;
- struct smb2_lease_break_work *lw;
-
- lw = kmalloc(sizeof(struct smb2_lease_break_work), GFP_KERNEL);
- if (!lw)
- return false;
-
- INIT_WORK(&lw->lease_break, cifs_ses_oplock_break);
- lw->lease_state = rsp->NewLeaseState;
+ struct cifs_pending_open *open;

cifs_dbg(FYI, "Checking for lease break\n");

@@ -607,11 +623,27 @@ smb2_is_valid_lease_break(char *buffer)
spin_lock(&tcon->open_file_lock);
cifs_stats_inc(
&tcon->stats.cifs_stats.num_oplock_brks);
- if (smb2_tcon_has_lease(tcon, rsp, lw)) {
+ if (smb2_tcon_has_lease(tcon, rsp)) {
spin_unlock(&tcon->open_file_lock);
spin_unlock(&cifs_tcp_ses_lock);
return true;
}
+ open = smb2_tcon_find_pending_open_lease(tcon,
+ rsp);
+ if (open) {
+ __u8 lease_key[SMB2_LEASE_KEY_SIZE];
+ struct tcon_link *tlink;
+
+ tlink = cifs_get_tlink(open->tlink);
+ memcpy(lease_key, open->lease_key,
+ SMB2_LEASE_KEY_SIZE);
+ spin_unlock(&tcon->open_file_lock);
+ spin_unlock(&cifs_tcp_ses_lock);
+ smb2_queue_pending_open_break(tlink,
+ lease_key,
+ rsp->NewLeaseState);
+ return true;
+ }
spin_unlock(&tcon->open_file_lock);

if (tcon->crfid.is_valid &&
@@ -629,7 +661,6 @@ smb2_is_valid_lease_break(char *buffer)
}
}
spin_unlock(&cifs_tcp_ses_lock);
- kfree(lw);
cifs_dbg(FYI, "Can not process lease break - no lease matched\n");
return false;
}