[PATCH] jfs: Extend the done of the window period

[Edward Adam Davis]

In lbmRead(), the I/O event waited for by wait_event() finishes before
it goes to sleep, and the lbmIODone() prematurely sets the flag to
lbmDONE, thus ending the wait. This causes wait_event() to return before
lbmREAD is cleared (because lbmDONE was set first), the premature return
of wait_event() leads to the release of lbuf before lbmIODone() returns,
thus triggering the use-after-free vulnerability reported in [1].

Moving the operation of setting the lbmDONE flag to after clearing lbmREAD
in lbmIODone() avoids the use-after-free vulnerability reported in [1].

[1]
BUG: KASAN: slab-use-after-free in rt_spin_lock+0x88/0x3e0 kernel/locking/spinlock_rt.c:56
Call Trace:
 blk_update_request+0x57e/0xe60 block/blk-mq.c:1007
 blk_mq_end_request+0x3e/0x70 block/blk-mq.c:1169
 blk_complete_reqs block/blk-mq.c:1244 [inline]
 blk_done_softirq+0x10a/0x160 block/blk-mq.c:1249

Allocated by task 6101:
 lbmLogInit fs/jfs/jfs_logmgr.c:1821 [inline]
 lmLogInit+0x3d0/0x19e0 fs/jfs/jfs_logmgr.c:1269
 open_inline_log fs/jfs/jfs_logmgr.c:1175 [inline]
 lmLogOpen+0x4e1/0xfa0 fs/jfs/jfs_logmgr.c:1069
 jfs_mount_rw+0xe9/0x670 fs/jfs/jfs_mount.c:257
 jfs_fill_super+0x754/0xd80 fs/jfs/super.c:532

Freed by task 6101:
 kfree+0x1bd/0x900 mm/slub.c:6876
 lbmLogShutdown fs/jfs/jfs_logmgr.c:1864 [inline]
 lmLogInit+0x1137/0x19e0 fs/jfs/jfs_logmgr.c:1415
 open_inline_log fs/jfs/jfs_logmgr.c:1175 [inline]
 lmLogOpen+0x4e1/0xfa0 fs/jfs/jfs_logmgr.c:1069
 jfs_mount_rw+0xe9/0x670 fs/jfs/jfs_mount.c:257
 jfs_fill_super+0x754/0xd80 fs/jfs/super.c:532

Reported-by: syzbot+1d38eedcb25a3b5686a7@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=1d38eedcb25a3b5686a7
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
---
 fs/jfs/jfs_logmgr.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index b343c5ea1159..dda9ffa8eaf5 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -2180,8 +2180,6 @@ static void lbmIODone(struct bio *bio)
 
 	LCACHE_LOCK(flags);		/* disable+lock */
 
-	bp->l_flag |= lbmDONE;
-
 	if (bio->bi_status) {
 		bp->l_flag |= lbmERROR;
 
@@ -2196,12 +2194,10 @@ static void lbmIODone(struct bio *bio)
 	if (bp->l_flag & lbmREAD) {
 		bp->l_flag &= ~lbmREAD;
 
-		LCACHE_UNLOCK(flags);	/* unlock+enable */
-
 		/* wakeup I/O initiator */
 		LCACHE_WAKEUP(&bp->l_ioevent);
 
-		return;
+		goto out;
 	}
 
 	/*
@@ -2225,8 +2221,7 @@ static void lbmIODone(struct bio *bio)
 
 	if (bp->l_flag & lbmDIRECT) {
 		LCACHE_WAKEUP(&bp->l_ioevent);
-		LCACHE_UNLOCK(flags);
-		return;
+		goto out;
 	}
 
 	tail = log->wqueue;
@@ -2278,8 +2273,6 @@ static void lbmIODone(struct bio *bio)
 	 * leave buffer for i/o initiator to dispose
 	 */
 	if (bp->l_flag & lbmSYNC) {
-		LCACHE_UNLOCK(flags);	/* unlock+enable */
-
 		/* wakeup I/O initiator */
 		LCACHE_WAKEUP(&bp->l_ioevent);
 	}
@@ -2288,7 +2281,6 @@ static void lbmIODone(struct bio *bio)
 	 *	Group Commit pageout:
 	 */
 	else if (bp->l_flag & lbmGC) {
-		LCACHE_UNLOCK(flags);
 		lmPostGC(bp);
 	}
 
@@ -2302,9 +2294,11 @@ static void lbmIODone(struct bio *bio)
 		assert(bp->l_flag & lbmRELEASE);
 		assert(bp->l_flag & lbmFREE);
 		lbmfree(bp);
-
-		LCACHE_UNLOCK(flags);	/* unlock+enable */
 	}
+
+out:
+	bp->l_flag |= lbmDONE;
+	LCACHE_UNLOCK(flags);
 }
 
 int jfsIOWait(void *arg)
-- 
2.43.0