Commit b64b6bf4 authored Apr 02, 2009 by Mikulas Patocka Committed by Alasdair G Kergon Apr 02, 2009

dm io: make sync_io uninterruptible



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@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

parent 95f8fac8

drivers/md/dm-io.c

+1 −4

Original line number	Diff line number	Diff line
		@@ -370,16 +370,13 @@ static int sync_io(struct dm_io_client *client, unsigned int num_regions,
		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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