Messages in this thread | | | From | Hillf Danton <> | Subject | Re: [syzbot] [kernfs?] possible deadlock in kernfs_seq_start | Date | Fri, 10 May 2024 07:26:13 +0800 |
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On Thu, 9 May 2024 17:52:21 +0300 Amir Goldstein <amir73il@gmail.com> > On Thu, May 9, 2024 at 1:49 PM Hillf Danton <hdanton@sina.com> wrote: > > > > The correct locking order is > > > > sb_writers > > This is sb of overlayfs > > > inode lock > > This is real inode > WRT sb_writers the order
lock inode parent lock inode kid
becomes lock inode kid sb_writers lock inode parent
given call trace
> -> #2 (sb_writers#4){.+.+}-{0:0}: > lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754 > percpu_down_read include/linux/percpu-rwsem.h:51 [inline] > __sb_start_write include/linux/fs.h:1664 [inline] > sb_start_write+0x4d/0x1c0 include/linux/fs.h:1800 > mnt_want_write+0x3f/0x90 fs/namespace.c:409 > ovl_create_object+0x13b/0x370 fs/overlayfs/dir.c:629 > lookup_open fs/namei.c:3497 [inline] > open_last_lookups fs/namei.c:3566 [inline]
and code snippet [1]
if (open_flag & O_CREAT) inode_lock(dir->d_inode); else inode_lock_shared(dir->d_inode); dentry = lookup_open(nd, file, op, got_write);
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/namei.c?id=dccb07f2914c#n3566
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