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dm io: fix a race condition in the wake up code for sync_io

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There's a race condition between the atomic_dec_and_test(&io->count)
in dec_count() and the waking of the sync_io() thread.  If the thread
is spuriously woken immediately after the decrement it may exit,
making the on stack io struct invalid, yet the dec_count could still
be using it.

Fix this race by using a completion in sync_io() and dec_count().

Reported-by: Minfei Huang <huangminfei@ucloud.cn>
Signed-off-by: Joe Thornber <thornber@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
This commit is contained in:
Joe Thornber 2014-06-27 15:29:04 -04:00 committed by Mike Snitzer
parent bf14299f1c
commit 10f1d5d111
1 changed files with 8 additions and 14 deletions
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22
drivers/md/dm-io.c
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@ -10,6 +10,7 @@
#include <linux/device-mapper.h>
#include <linux/bio.h>
#include <linux/completion.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/sched.h>
@ -32,7 +33,7 @@ struct dm_io_client {
struct io {
unsigned long error_bits;
atomic_t count;
struct task_struct *sleeper;
struct completion *wait;
struct dm_io_client *client;
io_notify_fn callback;
void *context;
@ -121,8 +122,8 @@ static void dec_count(struct io *io, unsigned int region, int error)
invalidate_kernel_vmap_range(io->vma_invalidate_address,
io->vma_invalidate_size);
if (io->sleeper)
wake_up_process(io->sleeper);
if (io->wait)
complete(io->wait);
else {
unsigned long r = io->error_bits;
@ -387,6 +388,7 @@ static int sync_io(struct dm_io_client *client, unsigned int num_regions,
*/
volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));
DECLARE_COMPLETION_ONSTACK(wait);
if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
WARN_ON(1);
@ -395,7 +397,7 @@ static int sync_io(struct dm_io_client *client, unsigned int num_regions,
io->error_bits = 0;
atomic_set(&io->count, 1); /* see dispatch_io() */
io->sleeper = current;
io->wait = &wait;
io->client = client;
io->vma_invalidate_address = dp->vma_invalidate_address;
@ -403,15 +405,7 @@ static int sync_io(struct dm_io_client *client, unsigned int num_regions,
dispatch_io(rw, num_regions, where, dp, io, 1);
while (1) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (!atomic_read(&io->count))
break;
io_schedule();
}
set_current_state(TASK_RUNNING);
wait_for_completion_io(&wait);
if (error_bits)
*error_bits = io->error_bits;
@ -434,7 +428,7 @@ static int async_io(struct dm_io_client *client, unsigned int num_regions,
io = mempool_alloc(client->pool, GFP_NOIO);
io->error_bits = 0;
atomic_set(&io->count, 1); /* see dispatch_io() */
io->sleeper = NULL;
io->wait = NULL;
io->client = client;
io->callback = fn;
io->context = context;