dm: fix use-after-free in dm_put_live_table_bio

dm_put_live_table_bio is called from the end of dm_submit_bio.
However, at this point, the bio may be already finished and the caller
may have freed the bio. Consequently, dm_put_live_table_bio accesses
the stale "bio" pointer.

Fix this bug by loading the bi_opf value and passing it to
dm_get_live_table_bio and dm_put_live_table_bio instead of the bio.

This bug was found by running the lvm2 testsuite with kasan.

Fixes: 7cb885820065 ("dm: introduce dm_{get,put}_live_table_bio called from dm_submit_bio")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index d5e6d33700e504113e5932f16012ba0ddde94da0..6ea14ab94aa60d67db21181ea50a6bd5e1a941ae 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -715,18 +715,18 @@ static void dm_put_live_table_fast(struct mapped_device *md) __releases(RCU)
 }
 
 static inline struct dm_table *dm_get_live_table_bio(struct mapped_device *md,
-                                                    int *srcu_idx, struct bio *bio)
+                                                    int *srcu_idx, unsigned bio_opf)
 {
-       if (bio->bi_opf & REQ_NOWAIT)
+       if (bio_opf & REQ_NOWAIT)
                return dm_get_live_table_fast(md);
        else
                return dm_get_live_table(md, srcu_idx);
 }
 
 static inline void dm_put_live_table_bio(struct mapped_device *md, int srcu_idx,
-                                        struct bio *bio)
+                                        unsigned bio_opf)
 {
-       if (bio->bi_opf & REQ_NOWAIT)
+       if (bio_opf & REQ_NOWAIT)
                dm_put_live_table_fast(md);
        else
                dm_put_live_table(md, srcu_idx);
@@ -1715,8 +1715,9 @@ static void dm_submit_bio(struct bio *bio)
        struct mapped_device *md = bio->bi_bdev->bd_disk->private_data;
        int srcu_idx;
        struct dm_table *map;
+       unsigned bio_opf = bio->bi_opf;
 
-       map = dm_get_live_table_bio(md, &srcu_idx, bio);
+       map = dm_get_live_table_bio(md, &srcu_idx, bio_opf);
 
        /* If suspended, or map not yet available, queue this IO for later */
        if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) ||
@@ -1732,7 +1733,7 @@ static void dm_submit_bio(struct bio *bio)
 
        dm_split_and_process_bio(md, map, bio);
 out:
-       dm_put_live_table_bio(md, srcu_idx, bio);
+       dm_put_live_table_bio(md, srcu_idx, bio_opf);
 }
 
 static bool dm_poll_dm_io(struct dm_io *io, struct io_comp_batch *iob,