From 16dfa6a5d048341435e7a0e9410047847a5dad1d Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Tue, 3 Dec 2019 07:53:15 -0800 Subject: [PATCH] xfs: fix mount failure crash on invalid iclog memory access [ Upstream commit 798a9cada4694ca8d970259f216cec47e675bfd5 ] syzbot (via KASAN) reports a use-after-free in the error path of xlog_alloc_log(). Specifically, the iclog freeing loop doesn't handle the case of a fully initialized ->l_iclog linked list. Instead, it assumes that the list is partially constructed and NULL terminated. This bug manifested because there was no possible error scenario after iclog list setup when the original code was added. Subsequent code and associated error conditions were added some time later, while the original error handling code was never updated. Fix up the error loop to terminate either on a NULL iclog or reaching the end of the list. Reported-by: syzbot+c732f8644185de340492@syzkaller.appspotmail.com Signed-off-by: Brian Foster Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong Signed-off-by: Sasha Levin --- fs/xfs/xfs_log.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index 33c9a3aae948..7bfcd09d446b 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -1540,6 +1540,8 @@ out_free_iclog: if (iclog->ic_bp) xfs_buf_free(iclog->ic_bp); kmem_free(iclog); + if (prev_iclog == log->l_iclog) + break; } spinlock_destroy(&log->l_icloglock); xfs_buf_free(log->l_xbuf); -- 2.20.1