Before this patch, btrfs raid56 will keep raid56 rbio even all its IO is
done.
This may save some time allocating rbio, but it can cause deadly
use-after-free bug, for the following case:
Original fs: 4 devices RAID5
Process A | Process B
--------------------------------------------------------------------------
| Start device replace
| Now the fs has 5 devices
| devid 0: replace device
| devid 1~4: old devices
btrfs_map_bio() |
|- __btrfs_map_block() |
| bbio has 5 stripes |
| including devid 0 |
|- raid56_parity_write() |
|
raid_write_end_io() |
|- rbio_orig_end_io() |
|- unlock_stripe() |
Keeps the old rbio for |
later steal, which has |
stripe for devid 0 |
| Cancel device replace
| Now the fs has 4 devices
| devid 0 is freed
Some IO happens |
raid_write_end_io() |
|- rbio_orig_end_io() |
|- unlock_stripe() |
|- steal_rbio() |
Use old rbio, whose |
bbio has freed devid 0|
stripe |
Any access to rbio->bbio will |
cause general protection or NULL |
pointer dereference |
Such bug can already be triggered by fstests btrfs/069 for RAID5/6
profiles.
Fix it by not keeping old rbio in unlock_stripe(), so we just free the
finished rbio and rbio->bbio, so above problem wont' happen.
Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
fs/btrfs/raid56.c | 18 +-----------------
1 file changed, 1 insertion(+), 17 deletions(-)
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index b8ffd9ea7499..41ced67165c0 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -774,7 +774,6 @@ static noinline void unlock_stripe(struct btrfs_raid_bio
*rbio)
int bucket;
struct btrfs_stripe_hash *h;
unsigned long flags;
- int keep_cache = 0;
bucket = rbio_bucket(rbio);
h = rbio->fs_info->stripe_hash_table->table + bucket;
@@ -786,19 +785,6 @@ static noinline void unlock_stripe(struct btrfs_raid_bio
*rbio)
spin_lock(&rbio->bio_list_lock);
if (!list_empty(&rbio->hash_list)) {
- /*
- * if we're still cached and there is no other IO
- * to perform, just leave this rbio here for others
- * to steal from later
- */
- if (list_empty(&rbio->plug_list) &&
- test_bit(RBIO_CACHE_BIT, &rbio->flags)) {
- keep_cache = 1;
- clear_bit(RBIO_RMW_LOCKED_BIT, &rbio->flags);
- BUG_ON(!bio_list_empty(&rbio->bio_list));
- goto done;
- }
-
list_del_init(&rbio->hash_list);
atomic_dec(&rbio->refs);
@@ -846,13 +832,11 @@ static noinline void unlock_stripe(struct btrfs_raid_bio
*rbio)
goto done_nolock;
}
}
-done:
spin_unlock(&rbio->bio_list_lock);
spin_unlock_irqrestore(&h->lock, flags);
done_nolock:
- if (!keep_cache)
- remove_rbio_from_cache(rbio);
+ remove_rbio_from_cache(rbio);
}
static void __free_raid_bio(struct btrfs_raid_bio *rbio)
--
2.11.0
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
