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authorIan Abbott <abbotti@mev.co.uk>2013-01-04 11:33:21 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-01-07 14:48:25 -0800
commitc0729eeefdcd76db338f635162bf0739fd2c5f6f (patch)
tree93325e4764bd7144631ff129b4e0f412f48d0d7f /drivers/staging
parent34ffb33e09132401872fe79e95c30824ce194d23 (diff)
staging: comedi: comedi_test: fix race when cancelling command
Éric Piel reported a kernel oops in the "comedi_test" module. It was a NULL pointer dereference within `waveform_ai_interrupt()` (actually a timer function) that sometimes occurred when a running asynchronous command is cancelled (either by the `COMEDI_CANCEL` ioctl or by closing the device file). This seems to be a race between the caller of `waveform_ai_cancel()` which on return from that function goes and tears down the running command, and the timer function which uses the command. In particular, `async->cmd.chanlist` gets freed (and the pointer set to NULL) by `do_become_nonbusy()` in "comedi_fops.c" but a previously scheduled `waveform_ai_interrupt()` timer function will dereference that pointer regardless, leading to the oops. Fix it by replacing the `del_timer()` call in `waveform_ai_cancel()` with `del_timer_sync()`. Signed-off-by: Ian Abbott <abbotti@mev.co.uk> Reported-by: Éric Piel <piel@delmic.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/staging')
-rw-r--r--drivers/staging/comedi/drivers/comedi_test.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/staging/comedi/drivers/comedi_test.c b/drivers/staging/comedi/drivers/comedi_test.c
index fb3d09323ba1..01de996239f1 100644
--- a/drivers/staging/comedi/drivers/comedi_test.c
+++ b/drivers/staging/comedi/drivers/comedi_test.c
@@ -345,7 +345,7 @@ static int waveform_ai_cancel(struct comedi_device *dev,
struct waveform_private *devpriv = dev->private;
devpriv->timer_running = 0;
- del_timer(&devpriv->timer);
+ del_timer_sync(&devpriv->timer);
return 0;
}