INFO: task hung in bfs_lookup on v7.3-rc2

INFO: task hung in bfs_lookup on v7.3-rc2

[CJ]

Hi,


I am reporting a hung task in bfs_lookup. It is still reproducible on
Linux v7.3-rc2 (HEAD df2908090cda368b01ff43709f51890076c56157) with a syzkaller reproducer.
syzbot originally reported "INFO: task hung in bfs_lookup" on linux-6.1
(https://syzkaller.appspot.com/bug?extid=329c4002dad0055b432b). The target console shows a matching failure signature.


The reproducer mounts a crafted BFS image and performs a directory lookup while another path holds the directory lock.


On the target, the kernel reports:
  INFO: task syz.0.11:9034 blocked for more than 143 seconds.


The diagnostic path is bfs_lookup -> d_alloc_parallel -> __d_lookup -> lookup_open.
The same blocked or diagnostic function path is present (bfs_lookup).


One possible cause is lock ordering between concurrent BFS directory operations.


This is a follow-up for an existing syzbot report and describes an
observed failure, not a bisected root cause.


Reproducer:
  syz reproducer: https://pastebin.com/raw/b6XKQqyN


console output: https://pastebin.com/raw/DE2p85x3
kernel config: https://syzkaller.appspot.com/text?tag=KernelConfig&x=ff93ecc085d8436e


Kernel:
  HEAD commit: df2908090cda368b01ff43709f51890076c56157
  git tree: linux-stable
  kernel version: 7.3.0-rc2
  tested tag: v7.3-rc2


Let me know if you need more details or testing.


Thanks.