On Thu, 1 Jun 2023 at 12:02, Pradeep Pragallapati <quic_pragalla@xxxxxxxxxxx> wrote: > > > On 5/31/2023 5:22 PM, Miklos Szeredi wrote: > > On Wed, 31 May 2023 at 11:26, Pradeep P V K <quic_pragalla@xxxxxxxxxxx> wrote: > >> There is a potential race/timing issue while aborting the > >> requests on processing list between fuse_dev_release() and > >> fuse_abort_conn(). This is resulting into below warnings > >> and can even result into UAF issues. > > Okay, but... > > > >> [22809.190255][T31644] refcount_t: underflow; use-after-free. > >> [22809.190266][T31644] WARNING: CPU: 2 PID: 31644 at lib/refcount.c:28 > >> refcount_warn_saturate+0x110/0x158 > >> ... > >> [22809.190567][T31644] Call trace: > >> [22809.190567][T31644] refcount_warn_saturate+0x110/0x158 > >> [22809.190569][T31644] fuse_file_put+0xfc/0x104 > > ...how can this cause the file refcount to underflow? That would > > imply that fuse_request_end() will be called for the same request > > twice. I can't see how that can happen with or without the locking > > change. > Please ignore this patch. i overlooked it as list_splice in > fuse_dev_release() and made the change. > > Do you have a reproducer? > > don't have exact/specific steps but i will try to recreate. This is > observed during stability testing (involves io, reboot, monkey, e.t.c.) > for 24hrs. So, far this is seen on both 5.15 and 6.1 kernels. Do you > have any points or speculations to share ? Do you have KASAN enabled in the kernel? That might help UAF issues easier. Thanks, Miklos
