On Fri, Aug 30, 2019 at 12:28:08PM -0700, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: ed858b88 Add linux-next specific files for 20190826 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=121b506c600000 > kernel config: https://syzkaller.appspot.com/x/.config?x=ee8373cd9733e305 > dashboard link: https://syzkaller.appspot.com/bug?extid=5bda120b4032f831c57f > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+5bda120b4032f831c57f@xxxxxxxxxxxxxxxxxxxxxxxxx > > ============================= > WARNING: suspicious RCU usage > 5.3.0-rc6-next-20190826 #73 Not tainted > ----------------------------- > fs/ext4/block_validity.c:333 suspicious rcu_dereference_check() usage! > #syz invalid There was already a fix applied between ed858b88 and latest linux-next: diff --git a/fs/ext4/block_validity.c b/fs/ext4/block_validity.c index 003dc1dc2da3..f7bc914a74df 100644 --- a/fs/ext4/block_validity.c +++ b/fs/ext4/block_validity.c @@ -330,11 +330,13 @@ void ext4_release_system_zone(struct super_block *sb) { struct ext4_system_blocks *system_blks; + rcu_read_lock(); system_blks = rcu_dereference(EXT4_SB(sb)->system_blks); rcu_assign_pointer(EXT4_SB(sb)->system_blks, NULL); if (system_blks) call_rcu(&system_blks->rcu, ext4_destroy_system_zone); + rcu_read_unlock(); }
