Re: [syzbot] [lsm?] [integrity?] possible deadlock in ima_file_truncate

On Mon, Aug 17, 2026 at 07:32:43PM -0400, Mimi Zohar wrote:
> On Mon, 2026-08-17 at 17:40 -0500, Frederick Lawler wrote:
> > On Mon, Aug 17, 2026 at 06:21:57PM -0400, Mimi Zohar wrote:
> > > On Mon, 2026-08-17 at 15:43 -0500, Frederick Lawler wrote:
> > > > On Sat, Aug 08, 2026 at 05:20:29PM -0700, syzbot wrote:
> > > > > Hello,
> > > > > 
> > > > > syzbot found the following issue on:
> > > > > 
> > > > > HEAD commit:    c21bb4193868 Merge tag 'for_linus' of git://git.kernel.org..
> > > > > git tree:       upstream
> > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=113c53b9580000
> > > > > kernel config:  https://syzkaller.appspot.com/x/.config?x=145fa60d73086782
> > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=448c2e24b1ceff13ed2a
> > > > > compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
> > > > > 
> > > > > Unfortunately, I don't have any reproducer for this issue yet.
> > > > > 
> > > > > Downloadable assets:
> > > > > disk image: https://storage.googleapis.com/syzbot-assets/dde4460fa7fd/disk-c21bb419.raw.xz
> > > > > vmlinux: https://storage.googleapis.com/syzbot-assets/e1fe13568a84/vmlinux-c21bb419.xz
> > > > > kernel image: https://storage.googleapis.com/syzbot-assets/283184100427/bzImage-c21bb419.xz
> > > > > 
> > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > > > Reported-by: [email protected]
> > > > > 
> > > > > ======================================================
> > > > > WARNING: possible circular locking dependency detected
> > > > > syzkaller #0 Not tainted
> > > > > ------------------------------------------------------
> > > > > syz.3.857/8643 is trying to acquire lock:
> > > > > ffff888037be2480 (&ima_iint_mutex_key[depth]){+.+.}-{4:4}, at: ima_reset_action_flags security/integrity/ima/ima_main.c:708 [inline]
> > > > > ffff888037be2480 (&ima_iint_mutex_key[depth]){+.+.}-{4:4}, at: ima_reset_action_flags security/integrity/ima/ima_main.c:697 [inline]
> > > > > ffff888037be2480 (&ima_iint_mutex_key[depth]){+.+.}-{4:4}, at: ima_file_truncate+0xe6/0x190 security/integrity/ima/ima_main.c:723
> > > > > 
> > > > > but task is already holding lock:
> > > > > ffff888035fc0450 (sb_writers#6){.+.+}-{0:0}, at: do_open fs/namei.c:4693 [inline]
> > > > > ffff888035fc0450 (sb_writers#6){.+.+}-{0:0}, at: path_openat+0x2929/0x4280 fs/namei.c:4863
> > > > > 
> > > > 
> > > > I had AI whip up a reproducer for this, but it's not mutually exclusive to the
> > > > added patch. Tested by running reproducer, then unapplied patch, still
> > > > reproduced on v7.2-rc4.
> > > > 
> > > > I'll need to simplify it before I post it.
> > > > 
> > > > #syz dup: [syzbot] [integrity?] [lsm?] possible deadlock in process_measurement (6)
> > > > 
> > > > See below for un-applied repro result.
> > > 
> > > Hi Fred,
> > > 
> > > In response to this syzbot, I responded:
> > 
> > Sorry, I must've missed that.
> > 
> > > Like other pseudo filesystems, configfs files should not be measured by IMA.  To
> > > addresss this particular bug, please add a rule to the builtin
> > > dont_measure_rules[] and default_appraise_rule[] policies.
> > > 
> > > Without the configfs filesystem being in policy, can you reproduce the deadlock?
> > 
> > I was not able to.
> 
> Do have time to post 2 patches - one to move the configfs magic number to
> magic.h and the other to update the IMA builtin policies?

Sure thing. Here's the post[1].

I rebased on linux-integrity/next-integrity.
(forgot to include that in cover)

Best,
Fred

[1]: https://lore.kernel.org/all/[email protected]/