Patch "ath9k: fix an invalid pointer dereference in ath9k_rng_stop()" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

ath9k: fix an invalid pointer dereference in ath9k_rng_stop()

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ath9k-fix-an-invalid-pointer-dereference-in-ath9k_rng_stop.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Miaoqing Pan <[email protected]>
Date: Tue, 27 Jun 2017 17:31:53 +0300
Subject: ath9k: fix an invalid pointer dereference in ath9k_rng_stop()

From: Miaoqing Pan <[email protected]>

commit 07246c115801c27652700e3679bb58661ef7ed65 upstream.

The bug was triggered when do suspend/resuming continuously on Dell XPS L322X/0PJHXN version 9333 (2013) with kernel 4.12.0-041200rc4-generic. But can't reproduce on DELL E5440 + AR9300 PCIE chips.

The warning is caused by accessing invalid pointer sc->rng_task. sc->rng_task is not be cleared after kthread_stop(sc->rng_task) be called in ath9k_rng_stop(). Because the kthread is stopped before ath9k_rng_kthread() be scheduled.

So set sc->rng_task to null after kthread_stop(sc->rng_task) to resolve this issue.

WARNING: CPU: 0 PID: 984 at linux/kernel/kthread.c:71 kthread_stop+0xf1/0x100
CPU: 0 PID: 984 Comm: NetworkManager Not tainted 4.12.0-041200rc4-generic #201706042031
Hardware name: Dell Inc.          Dell System XPS L322X/0PJHXN, BIOS A09 05/15/2013
task: ffff950170fdda00 task.stack: ffffa22c01538000
RIP: 0010:kthread_stop+0xf1/0x100
RSP: 0018:ffffa22c0153b5b0 EFLAGS: 00010246
RAX: ffffffffa6257800 RBX: ffff950171b79560 RCX: 0000000000000000
RDX: 0000000080000000 RSI: 000000007fffffff RDI: ffff9500ac9a9680
RBP: ffffa22c0153b5c8 R08: 0000000000000000 R09: 0000000000000000
R10: ffffa22c0153b648 R11: ffff9501768004b8 R12: ffff9500ac9a9680
R13: ffff950171b79f70 R14: ffff950171b78780 R15: ffff9501749dc018
FS:  00007f0d6bfd5540(0000) GS:ffff95017f200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc190161a08 CR3: 0000000232906000 CR4: 00000000001406f0
Call Trace:
  ath9k_rng_stop+0x1a/0x20 [ath9k]
  ath9k_stop+0x3b/0x1d0 [ath9k]
  drv_stop+0x33/0xf0 [mac80211]
  ieee80211_stop_device+0x43/0x50 [mac80211]
  ieee80211_do_stop+0x4f2/0x810 [mac80211]

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=196043

---
 drivers/net/wireless/ath/ath9k/rng.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

@@ -120,6 +120,8 @@ void ath9k_rng_start(struct ath_softc *s
 
 void ath9k_rng_stop(struct ath_softc *sc)
 {
-	if (sc->rng_task)
+	if (sc->rng_task) {
 		kthread_stop(sc->rng_task);
+		sc->rng_task = NULL;
+	}
 }

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/ath9k-fix-an-invalid-pointer-dereference-in-ath9k_rng_stop.patch queue-4.9/ath9k-fix-tx99-use-after-free.patch queue-4.9/ath9k-fix-tx99-bus-error.patch