Re: [syzbot] [jfs?] KASAN: slab-use-after-free Read in jfs_syncpt

[Edward Adam Davis]

please test uaf in jfs_syncpt

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

diff --git a/fs/jfs/jfs_incore.h b/fs/jfs/jfs_incore.h
index dd4264aa9bed..15955dd86bfd 100644
--- a/fs/jfs/jfs_incore.h
+++ b/fs/jfs/jfs_incore.h
@@ -197,6 +197,7 @@ struct jfs_sb_info {
 	kgid_t		gid;		/* gid to override on-disk gid */
 	uint		umask;		/* umask to override on-disk umask */
 	uint		minblks_trim;	/* minimum blocks, for online trim */
+	struct mutex log_mutex;
 };
 
 /* jfs_sb_info commit_state */
diff --git a/fs/jfs/jfs_txnmgr.c b/fs/jfs/jfs_txnmgr.c
index be17e3c43582..bd30b93e435c 100644
--- a/fs/jfs/jfs_txnmgr.c
+++ b/fs/jfs/jfs_txnmgr.c
@@ -2665,6 +2665,9 @@ static void txLazyCommit(struct tblock * tblk)
 
 	log = (struct jfs_log *) JFS_SBI(tblk->sb)->log;
 
+	if (!log)
+		return;
+
 	spin_lock_irq(&log->gclock);	// LOGGC_LOCK
 
 	tblk->flag |= tblkGC_COMMITTED;
@@ -2730,7 +2733,9 @@ int jfs_lazycommit(void *arg)
 				list_del(&tblk->cqueue);
 
 				LAZY_UNLOCK(flags);
+				mutex_lock(&sbi->log_mutex);
 				txLazyCommit(tblk);
+				mutex_unlock(&sbi->log_mutex);
 				LAZY_LOCK(flags);
 
 				sbi->commit_state &= ~IN_LAZYCOMMIT;
diff --git a/fs/jfs/jfs_umount.c b/fs/jfs/jfs_umount.c
index 8ec43f53f686..04788cf3a471 100644
--- a/fs/jfs/jfs_umount.c
+++ b/fs/jfs/jfs_umount.c
@@ -51,6 +51,7 @@ int jfs_umount(struct super_block *sb)
 	 *
 	 * if mounted read-write and log based recovery was enabled
 	 */
+	mutex_lock(&sbi->log_mutex);
 	if ((log = sbi->log))
 		/*
 		 * Wait for outstanding transactions to be written to log:
@@ -113,6 +114,7 @@ int jfs_umount(struct super_block *sb)
 		 */
 		rc = lmLogClose(sb);
 	}
+	mutex_unlock(&sbi->log_mutex);
 	jfs_info("UnMount JFS Complete: rc = %d", rc);
 	return rc;
 }
diff --git a/fs/jfs/super.c b/fs/jfs/super.c
index 8d8e556bd610..cf291bdd094f 100644
--- a/fs/jfs/super.c
+++ b/fs/jfs/super.c
@@ -504,6 +504,7 @@ static int jfs_fill_super(struct super_block *sb, void *data, int silent)
 	sbi->uid = INVALID_UID;
 	sbi->gid = INVALID_GID;
 	sbi->umask = -1;
+	mutex_init(&sbi->log_mutex);
 
 	/* initialize the mount flag and determine the default error handler */
 	flag = JFS_ERR_REMOUNT_RO;