On Tue 10-01-23 12:27:09, Baokun Li wrote: > Syzbot reported a hung task problem: > ================================================================== > INFO: task syz-executor232:5073 blocked for more than 143 seconds. > Not tainted 6.2.0-rc2-syzkaller-00024-g512dee0c00ad #0 > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > task:syz-exec232 state:D stack:21024 pid:5073 ppid:5072 flags:0x00004004 > Call Trace: > <TASK> > context_switch kernel/sched/core.c:5244 [inline] > __schedule+0x995/0xe20 kernel/sched/core.c:6555 > schedule+0xcb/0x190 kernel/sched/core.c:6631 > __wait_on_freeing_inode fs/inode.c:2196 [inline] > find_inode_fast+0x35a/0x4c0 fs/inode.c:950 > iget_locked+0xb1/0x830 fs/inode.c:1273 > __ext4_iget+0x22e/0x3ed0 fs/ext4/inode.c:4861 > ext4_xattr_inode_iget+0x68/0x4e0 fs/ext4/xattr.c:389 > ext4_xattr_inode_dec_ref_all+0x1a7/0xe50 fs/ext4/xattr.c:1148 > ext4_xattr_delete_inode+0xb04/0xcd0 fs/ext4/xattr.c:2880 > ext4_evict_inode+0xd7c/0x10b0 fs/ext4/inode.c:296 > evict+0x2a4/0x620 fs/inode.c:664 > ext4_orphan_cleanup+0xb60/0x1340 fs/ext4/orphan.c:474 > __ext4_fill_super fs/ext4/super.c:5516 [inline] > ext4_fill_super+0x81cd/0x8700 fs/ext4/super.c:5644 > get_tree_bdev+0x400/0x620 fs/super.c:1282 > vfs_get_tree+0x88/0x270 fs/super.c:1489 > do_new_mount+0x289/0xad0 fs/namespace.c:3145 > do_mount fs/namespace.c:3488 [inline] > __do_sys_mount fs/namespace.c:3697 [inline] > __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3674 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > RIP: 0033:0x7fa5406fd5ea > RSP: 002b:00007ffc7232f968 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fa5406fd5ea > RDX: 0000000020000440 RSI: 0000000020000000 RDI: 00007ffc7232f970 > RBP: 00007ffc7232f970 R08: 00007ffc7232f9b0 R09: 0000000000000432 > R10: 0000000000804a03 R11: 0000000000000202 R12: 0000000000000004 > R13: 0000555556a7a2c0 R14: 00007ffc7232f9b0 R15: 0000000000000000 > </TASK> > ================================================================== > > The problem is that the inode contains an xattr entry with ea_inum of 15 > when cleaning up an orphan inode <15>. When evict inode <15>, the reference > counting of the corresponding EA inode is decreased. When EA inode <15> is > found by find_inode_fast() in __ext4_iget(), it is found that the EA inode > holds the I_FREEING flag and waits for the EA inode to complete deletion. > As a result, when inode <15> is being deleted, we wait for inode <15> to > complete the deletion, resulting in an infinite loop and triggering Hung > Task. To solve this problem, we only need to check whether the ino of EA > inode and parent is the same before getting EA inode. > > Link: https://syzkaller.appspot.com/bug?extid=77d6fcc37bbb92f26048 > Reported-by: syzbot+77d6fcc37bbb92f26048@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx> > --- > fs/ext4/xattr.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c > index 7decaaf27e82..9ff8fcf78bb8 100644 > --- a/fs/ext4/xattr.c > +++ b/fs/ext4/xattr.c > @@ -386,6 +386,13 @@ static int ext4_xattr_inode_iget(struct inode *parent, unsigned long ea_ino, > struct inode *inode; > int err; > Perhaps add a comment here like: /* * We have to check for this corruption early as otherwise * iget_locked() could wait indefinitely for the state of our * parent inode. */ > + if (parent->i_ino == ea_ino) { > + ext4_error(parent->i_sb, > + "Parent and EA inode have the same ino %lu", ea_ino); > + err = -EUCLEAN; ^^ I prefer -EFSCORRUPTED here. It is the same value but more descriptive name :). > + goto error; ^^ Just "return err" here. This will try to iput() uninitialized pointer. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
