[PATCH] USB: cdc-wdm: fix lockup on error in wdm_read

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Clear the WDM_READ flag on errors and empty reads to avoid
running forever in an infinite tight loop, causing lockups:

Jul  1 21:58:11 nemi kernel: [ 3658.898647] qmi_wwan 2-1:1.2: Unexpected error -71
Jul  1 21:58:36 nemi kernel: [ 3684.072021] BUG: soft lockup - CPU#0 stuck for 23s! [qmi.pl:12235]
Jul  1 21:58:36 nemi kernel: [ 3684.072212] CPU 0
Jul  1 21:58:36 nemi kernel: [ 3684.072355]
Jul  1 21:58:36 nemi kernel: [ 3684.072367] Pid: 12235, comm: qmi.pl Tainted: P           O 3.5.0-rc2+ #13 LENOVO 2776LEG/2776LEG
Jul  1 21:58:36 nemi kernel: [ 3684.072383] RIP: 0010:[<ffffffffa0635008>]  [<ffffffffa0635008>] spin_unlock_irq+0x8/0xc [cdc_wdm]
Jul  1 21:58:36 nemi kernel: [ 3684.072388] RSP: 0018:ffff88022dca1e70  EFLAGS: 00000282
Jul  1 21:58:36 nemi kernel: [ 3684.072393] RAX: ffff88022fc3f650 RBX: ffffffff811c56f7 RCX: 00000001000ce8c1
Jul  1 21:58:36 nemi kernel: [ 3684.072398] RDX: 0000000000000010 RSI: 000000000267d810 RDI: ffff88022fc3f650
Jul  1 21:58:36 nemi kernel: [ 3684.072403] RBP: ffff88022dca1eb0 R08: ffffffffa063578e R09: 0000000000000000
Jul  1 21:58:36 nemi kernel: [ 3684.072407] R10: 0000000000000008 R11: 0000000000000246 R12: 0000000000000002
Jul  1 21:58:36 nemi kernel: [ 3684.072412] R13: 0000000000000246 R14: ffffffff00000002 R15: ffff8802281d8c88
Jul  1 21:58:36 nemi kernel: [ 3684.072418] FS:  00007f666a260700(0000) GS:ffff88023bc00000(0000) knlGS:0000000000000000
Jul  1 21:58:36 nemi kernel: [ 3684.072423] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Jul  1 21:58:36 nemi kernel: [ 3684.072428] CR2: 000000000270d9d8 CR3: 000000022e865000 CR4: 00000000000007f0
Jul  1 21:58:36 nemi kernel: [ 3684.072433] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
Jul  1 21:58:36 nemi kernel: [ 3684.072438] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Jul  1 21:58:36 nemi kernel: [ 3684.072444] Process qmi.pl (pid: 12235, threadinfo ffff88022dca0000, task ffff88022ff76380)
Jul  1 21:58:36 nemi kernel: [ 3684.072448] Stack:
Jul  1 21:58:36 nemi kernel: [ 3684.072458]  ffffffffa063592e 0000000100020000 ffff88022fc3f650 ffff88022fc3f6a8
Jul  1 21:58:36 nemi kernel: [ 3684.072466]  0000000000000200 0000000100000000 000000000267d810 0000000000000000
Jul  1 21:58:36 nemi kernel: [ 3684.072475]  0000000000000000 ffff880212cfb6d0 0000000000000200 ffff880212cfb6c0
Jul  1 21:58:36 nemi kernel: [ 3684.072479] Call Trace:
Jul  1 21:58:36 nemi kernel: [ 3684.072489]  [<ffffffffa063592e>] ? wdm_read+0x1a0/0x263 [cdc_wdm]
Jul  1 21:58:36 nemi kernel: [ 3684.072500]  [<ffffffff8110adb7>] ? vfs_read+0xa1/0xfb
Jul  1 21:58:36 nemi kernel: [ 3684.072509]  [<ffffffff81040589>] ? alarm_setitimer+0x35/0x64
Jul  1 21:58:36 nemi kernel: [ 3684.072517]  [<ffffffff8110aec7>] ? sys_read+0x45/0x6e
Jul  1 21:58:36 nemi kernel: [ 3684.072525]  [<ffffffff813725f9>] ? system_call_fastpath+0x16/0x1b
Jul  1 21:58:36 nemi kernel: [ 3684.072557] Code: <66> 66 90 c3 83 ff ed 89 f8 74 16 7f 06 83 ff a1 75 0a c3 83 ff f4

The WDM_READ flag is normally cleared by wdm_int_callback
before resubmitting the interrupt urb.  But a crashing
device may cause both a read error and cancelling all
urbs.  We must make sure that the flag is cleared by
wdm_read in this case.

Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Bjørn Mork <bjorn@xxxxxxx>
---
 drivers/usb/class/cdc-wdm.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index 25e7d72..f77a631 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -461,6 +461,8 @@ retry:
 		spin_lock_irq(&desc->iuspin);
 
 		if (desc->rerr) { /* read completed, error happened */
+			dev_dbg(&desc->intf->dev, "%s: error - clearing WDM_READ\n", __func__);
+			clear_bit(WDM_READ, &desc->flags);
 			desc->rerr = 0;
 			spin_unlock_irq(&desc->iuspin);
 			rv = -EIO;
@@ -475,6 +477,8 @@ retry:
 			goto retry;
 		}
 		if (!desc->reslength) { /* zero length read */
+			dev_dbg(&desc->intf->dev, "%s: zero length - clearing WDM_READ\n", __func__);
+			clear_bit(WDM_READ, &desc->flags);
 			spin_unlock_irq(&desc->iuspin);
 			goto retry;
 		}
-- 
1.7.10

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B and H Foto and Electronics Corp.

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