Re: [syzbot] [cgroups?] general protection fault in __cgroup_rstat_lock

Re: [syzbot] [cgroups?] general protection fault in __cgroup_rstat_lock

[syzbot]

syzbot suspects this issue was fixed by commit:

commit a97915559f5c5ff1972d678b94fd460c72a3b5f2
Author: JP Kobryn <inwardvessel@gmail.com>
Date:   Fri Apr 4 01:10:48 2025 +0000

    cgroup: change rstat function signatures from cgroup-based to css-based

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12ca4c82580000
start commit:   932fc2f19b74 Merge branch 'irq-save-restore'
git tree:       bpf-next
kernel config:  https://syzkaller.appspot.com/x/.config?x=50c7a61469ce77e7
dashboard link: https://syzkaller.appspot.com/bug?extid=31eb4d4e7d9bc1fc1312
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=161cdfc0580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12dfc8df980000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: cgroup: change rstat function signatures from cgroup-based to css-based

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Re: [syzbot] [cgroups?] general protection fault in __cgroup_rstat_lock

[Michal Koutný]

[-- Attachment #1: Type: text/plain, Size: 882 bytes --]

On Sun, Jun 01, 2025 at 09:21:02AM -0700, syzbot <syzbot+31eb4d4e7d9bc1fc1312@syzkaller.appspotmail.com> wrote:
> syzbot suspects this issue was fixed by commit:
> 
> commit a97915559f5c5ff1972d678b94fd460c72a3b5f2
> Author: JP Kobryn <inwardvessel@gmail.com>
> Date:   Fri Apr 4 01:10:48 2025 +0000
> 
>     cgroup: change rstat function signatures from cgroup-based to css-based

It says: "This non-functional change serves..."

However, it moves the *_rstat_init in cgroup_create() after kernfs dir
creation and given the reproducer has a fault injected:
	mkdir(&(0x7f0000000000)='./cgroup/file0\x00', 0xd0939199c36b4d28) (fail_nth: 8)

I'd say this might be relevant (although I don't see the possibly
incorrect error handlnig path) but it doesn't mean this commit fixes it,
it'd rather require the reproducer to adjust the N on this path.

0.02€,
Michal

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

Re: [syzbot] [cgroups?] general protection fault in __cgroup_rstat_lock

[Michal Koutný]

[-- Attachment #1: Type: text/plain, Size: 680 bytes --]

On Mon, Jun 02, 2025 at 04:15:56PM +0200, Michal Koutný <mkoutny@suse.com> wrote:
> I'd say this might be relevant (although I don't see the possibly
> incorrect error handlnig path) but it doesn't mean this commit fixes it,
> it'd rather require the reproducer to adjust the N on this path.

Hm, possibly syzbot caught up here [1]:

-mkdir(&(0x7f0000000000)='./cgroup/file0\x00', 0xd0939199c36b4d28) (fail_nth: 8)
+mkdirat$cgroup_root(0xffffffffffffff9c, &(0x7f00000005c0)='./cgroup.net/syz0\x00', 0x1ff) (fail_nth: 23)

So there's something fishy in the error handling.

HTH,
Michal

[1] https://lore.kernel.org/lkml/68403875.a00a0220.d4325.000a.GAE@google.com/

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]