If someone sends signal to a process performing synchronous dm-io call,
the kernel may crash.
The function sync_io attempts to exit with -EINTR if it has pending signal,
however the structure "io" is allocated on stack, so already submitted io
requests end up touching unallocated stack space and corrupting kernel memory.
sync_io sets its state to TASK_UNINTERRUPTIBLE, so the signal can't break out
of io_schedule() --- however, if the signal was pending before sync_io entered
while (1) loop, the corruption of kernel memory will happen.
There is no way to cancel in-progress IOs, so the best solution is to ignore
signals at this point.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
---
drivers/md/dm-io.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
Index: linux-2.6.29-rc1-devel/drivers/md/dm-io.c
===================================================================
--- linux-2.6.29-rc1-devel.orig/drivers/md/dm-io.c 2009-01-22 03:46:09.000000000 +0100
+++ linux-2.6.29-rc1-devel/drivers/md/dm-io.c 2009-01-22 03:46:50.000000000 +0100
@@ -368,16 +368,13 @@ static int sync_io(struct dm_io_client *
while (1) {
set_current_state(TASK_UNINTERRUPTIBLE);
- if (!atomic_read(&io.count) || signal_pending(current))
+ if (!atomic_read(&io.count))
break;
io_schedule();
}
set_current_state(TASK_RUNNING);
- if (atomic_read(&io.count))
- return -EINTR;
-
if (error_bits)
*error_bits = io.error_bits;
--
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