Re: [PATCH 5.15.y] ocfs2: fix deadlock in ocfs2_get_system_file_inode

Pranav Tyagi
2025-07-12T17:12:03Z

On Sat, Jul 12, 2025 at 7:16 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Mon, Jun 30, 2025 at 02:05:42PM +0530, Pranav Tyagi wrote:
> > From: Mohammed Anees <pvmohammedanees2003@gmail.com>
> >
> > [ Upstream commit 7bf1823e010e8db2fb649c790bd1b449a75f52d8 ]
> >
> > syzbot has found a possible deadlock in ocfs2_get_system_file_inode [1].
> >
> > The scenario is depicted here,
> >
> > CPU0 CPU1
> > lock(&ocfs2_file_ip_alloc_sem_key);
> > lock(&osb->system_file_mutex);
> > lock(&ocfs2_file_ip_alloc_sem_key);
> > lock(&osb->system_file_mutex);
> >
> > The function calls which could lead to this are:
> >
> > CPU0
> > ocfs2_mknod - lock(&ocfs2_file_ip_alloc_sem_key);
> > .
> > .
> > .
> > ocfs2_get_system_file_inode - lock(&osb->system_file_mutex);
> >
> > CPU1 -
> > ocfs2_fill_super - lock(&osb->system_file_mutex);
> > .
> > .
> > .
> > ocfs2_read_virt_blocks - lock(&ocfs2_file_ip_alloc_sem_key);
> >
> > This issue can be resolved by making the down_read -> down_read_try
> > in the ocfs2_read_virt_blocks.
> >
> > [1] https://syzkaller.appspot.com/bug?extid=e0055ea09f1f5e6fabdd
> >
> > [ Backport to 5.15: context cleanly applied with no semantic changes.
> > Build-tested. ]
>
> We can't take a 5.15.y version, without it being in 6.1.y first, sorry
> :(
>

Hi,

Thanks for pointing that out. I wasn’t aware of the 6.1.y prerequisite
for 5.15.y backports. Learned something new today. I’ll make sure to get
it into 6.1.y first.

Regards
Pranav Tyagi