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Subject: Re: [syzbot] [jfs?] KASAN: use-after-free Read in jfs_lazycommit
Author: tristmd@gmail.com

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index 306165e61438c..855d58210b12a 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -1806,6 +1806,7 @@ static int lbmLogInit(struct jfs_log * log)
 	init_waitqueue_head(&log->free_wait);
 
 	log->lbuf_free = NULL;
+	atomic_set(&log->pending_io, 0);
 
 	for (i = 0; i < LOGPAGES;) {
 		char *buffer;
@@ -1855,6 +1856,8 @@ static void lbmLogShutdown(struct jfs_log * log)
 
 	jfs_info("lbmLogShutdown: log:0x%p", log);
 
+	wait_event(log->free_wait, atomic_read(&log->pending_io) == 0);
+
 	lbuf = log->lbuf_free;
 	while (lbuf) {
 		struct lbuf *next = lbuf->l_freelist;
@@ -1976,6 +1979,7 @@ static int lbmRead(struct jfs_log * log, int pn, struct lbuf ** bpp)
 
 	bio->bi_end_io = lbmIODone;
 	bio->bi_private = bp;
+	atomic_inc(&log->pending_io);
 	/*check if journaling to disk has been disabled*/
 	if (log->no_integrity) {
 		bio->bi_iter.bi_size = 0;
@@ -2122,6 +2126,7 @@ static void lbmStartIO(struct lbuf * bp)
 
 	bio->bi_end_io = lbmIODone;
 	bio->bi_private = bp;
+	atomic_inc(&log->pending_io);
 
 	/* check if journaling to disk has been disabled */
 	if (log->no_integrity) {
@@ -2186,6 +2191,8 @@ static void lbmIODone(struct bio *bio)
 
 	bio_put(bio);
 
+	log = bp->l_log;
+
 	/*
 	 *	pagein completion
 	 */
@@ -2214,7 +2221,6 @@ static void lbmIODone(struct bio *bio)
 	INCREMENT(lmStat.pagedone);
 
 	/* update committed lsn */
-	log = bp->l_log;
 	log->clsn = (bp->l_pn << L2LOGPSIZE) + bp->l_ceor;
 
 	if (bp->l_flag & lbmDIRECT) {
@@ -2297,6 +2303,8 @@ static void lbmIODone(struct bio *bio)
 	}
 
 out:
+	if (atomic_dec_and_test(&log->pending_io))
+		wake_up(&log->free_wait);
 	bp->l_flag |= lbmDONE;
 	LCACHE_UNLOCK(flags);
 }
diff --git a/fs/jfs/jfs_logmgr.h b/fs/jfs/jfs_logmgr.h
index 09e0ef6aeccef..df0375ce572f8 100644
--- a/fs/jfs/jfs_logmgr.h
+++ b/fs/jfs/jfs_logmgr.h
@@ -400,6 +400,7 @@ struct jfs_log {
 	uuid_t uuid;		/* 16: 128-bit uuid of log device */
 
 	int no_integrity;	/* 3: flag to disable journaling to disk */
+	atomic_t pending_io;	/* count of in-flight log I/Os */
 };
 
 /*