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Subject[PATCH 4.12 008/196] ath9k: fix an invalid pointer dereference in ath9k_rng_stop()
4.12-stable review patch.  If anyone has any objections, please let me know.


From: Miaoqing Pan <>

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]

Reported-by: Giulio Genovese <>
Tested-by: Giulio Genovese <>
Signed-off-by: Miaoqing Pan <>
Signed-off-by: Kalle Valo <>
Signed-off-by: Greg Kroah-Hartman <>

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

--- a/drivers/net/wireless/ath/ath9k/rng.c
+++ b/drivers/net/wireless/ath/ath9k/rng.c
@@ -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) {
+ sc->rng_task = NULL;
+ }

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