[patch 037/100] dm io: make sync_io uninterruptible

[Chris Wright]

-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Mikulas Patocka <mpatocka@xxxxxxxxxx>

upstream commit: b64b6bf4fd8b678a9f8477c11773c38a0a246a6d

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.

Cc: stable@xxxxxxxxxx
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Alasdair G Kergon <agk@xxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
---
 drivers/md/dm-io.c |    5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -370,16 +370,13 @@ 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;
 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/