RE: [syzbot] [rdma?] KASAN: slab-use-after-free Read in siw_query_port (2)

Bernard Metzler
2024-12-02T17:08:14Z

> -----Original Message-----
> From: Leon Romanovsky <leon@kernel.org>
> Sent: Thursday, November 28, 2024 10:37 AM
> To: Bernard Metzler <BMT@zurich.ibm.com>
> Cc: jgg@ziepe.ca; linux-rdma@vger.kernel.org; zyjzyj2000@gmail.com
> Subject: [EXTERNAL] Re: [syzbot] [rdma?] KASAN: slab-use-after-free Read in
> siw_query_port (2)
>
> On Wed, Nov 27, 2024 at 12:57:45PM +0000, Bernard Metzler wrote:
> >
> >
> > > -----Original Message-----
> > > From: syzbot <syzbot+67a887427af54ecb7c93@syzkaller.appspotmail.com>
> > > Sent: Wednesday, November 27, 2024 10:49 AM
> > > To: Bernard Metzler <BMT@zurich.ibm.com>; jgg@ziepe.ca;
> leon@kernel.org;
> > > linux-kernel@vger.kernel.org; linux-rdma@vger.kernel.org;
> > > netdev@vger.kernel.org; syzkaller-bugs@googlegroups.com
> > > Subject: [EXTERNAL] [syzbot] [rdma?] KASAN: slab-use-after-free Read in
> > > siw_query_port (2)
> > >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit: 5d066766c5f1 net/l2tp: fix warning in l2tp_exit_net
> found
> > > ..
> > > git tree: net
> > > console output: https%
> > > 3A__syzkaller.appspot.com_x_log.txt-3Fx-
> > >
> 3D168e8dc0580000&d=DwIBaQ&c=BSDicqBQBDjDI9RkVyTcHQ&r=4ynb4Sj_4MUcZXbhvovE4t
> > >
> YSbqxyOwdSiLedP4yO55g&m=m3O6vMc9WMuoczjDeT5i4qksFSps2rP3_ATMJw2E343vFsIyyHx
> > > 17mPmc2wtJaU4&s=6au3yUVQofLXZAr8nH0sfWV1MtQx2Z16Nk9rsXOeVFs&e=
> > > kernel config: https%
> > > 3A__syzkaller.appspot.com_x_.config-3Fx-
> > >
> 3D83e9a7f9e94ea674&d=DwIBaQ&c=BSDicqBQBDjDI9RkVyTcHQ&r=4ynb4Sj_4MUcZXbhvovE
> > >
> 4tYSbqxyOwdSiLedP4yO55g&m=m3O6vMc9WMuoczjDeT5i4qksFSps2rP3_ATMJw2E343vFsIyy
> > > Hx17mPmc2wtJaU4&s=n9aCEUutAWKdDNujKIupw82TQQSlr_TZcMgisng0Xus&e=
> > > dashboard link: https%
> > > 3A__syzkaller.appspot.com_bug-3Fextid-
> > >
> 3D67a887427af54ecb7c93&d=DwIBaQ&c=BSDicqBQBDjDI9RkVyTcHQ&r=4ynb4Sj_4MUcZXbh
> > >
> vovE4tYSbqxyOwdSiLedP4yO55g&m=m3O6vMc9WMuoczjDeT5i4qksFSps2rP3_ATMJw2E343vF
> > > sIyyHx17mPmc2wtJaU4&s=7f-Omz7ps-pKM3jhyCcKlwMASxX_kB_Sd_pAF-Jvpxg&e=
> > > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for
> > > Debian) 2.40
> > > syz repro: https%
> > > 3A__syzkaller.appspot.com_x_repro.syz-3Fx-
> > >
> 3D11355530580000&d=DwIBaQ&c=BSDicqBQBDjDI9RkVyTcHQ&r=4ynb4Sj_4MUcZXbhvovE4t
> > >
> YSbqxyOwdSiLedP4yO55g&m=m3O6vMc9WMuoczjDeT5i4qksFSps2rP3_ATMJw2E343vFsIyyHx
> > > 17mPmc2wtJaU4&s=fZra1eeMYqeDiaYg5CltF9l2fz28wKtU-yI_jEtubGg&e=
> > >
> > > Downloadable assets:
> > > disk image: https%
> > > 3A__storage.googleapis.com_syzbot-2Dassets_ba9b7c97759c_disk-
> > >
> 2D5d066766.raw.xz&d=DwIBaQ&c=BSDicqBQBDjDI9RkVyTcHQ&r=4ynb4Sj_4MUcZXbhvovE4
> > >
> tYSbqxyOwdSiLedP4yO55g&m=m3O6vMc9WMuoczjDeT5i4qksFSps2rP3_ATMJw2E343vFsIyyH
> > > x17mPmc2wtJaU4&s=4ypBicdKG1ksPIkOu2OLcppS8J0vPN08wFzXHtyvNEE&e=
> > > vmlinux: https%
> > > 3A__storage.googleapis.com_syzbot-2Dassets_92a30584a5ad_vmlinux-
> > >
> 2D5d066766.xz&d=DwIBaQ&c=BSDicqBQBDjDI9RkVyTcHQ&r=4ynb4Sj_4MUcZXbhvovE4tYSb
> > >
> qxyOwdSiLedP4yO55g&m=m3O6vMc9WMuoczjDeT5i4qksFSps2rP3_ATMJw2E343vFsIyyHx17m
> > > Pmc2wtJaU4&s=YyIgS6-_sljSEl3L1KN4bsGRpSJUuXDDkf1lrONXgNE&e=
> > > kernel image: https%
> > > 3A__storage.googleapis.com_syzbot-2Dassets_88d717deaf07_bzImage-
> > >
> 2D5d066766.xz&d=DwIBaQ&c=BSDicqBQBDjDI9RkVyTcHQ&r=4ynb4Sj_4MUcZXbhvovE4tYSb
> > >
> qxyOwdSiLedP4yO55g&m=m3O6vMc9WMuoczjDeT5i4qksFSps2rP3_ATMJw2E343vFsIyyHx17m
> > > Pmc2wtJaU4&s=hNlNLIJQasRBAom2wakJesBp-oiI9FnXezvbtTzPW34&e=
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the
> > > commit:
> > > Reported-by: syzbot+67a887427af54ecb7c93@syzkaller.appspotmail.com
> > >
> > > xfrm0 speed is unknown, defaulting to 1000
> > > ==================================================================
> > > BUG: KASAN: slab-use-after-free in siw_query_port+0x348/0x440
> > > drivers/infiniband/sw/siw/siw_verbs.c:183
> > > Read of size 4 at addr ffff88802ff88038 by task kworker/0:5/5883
> > >
> > > CPU: 0 UID: 0 PID: 5883 Comm: kworker/0:5 Not tainted 6.12.0-syzkaller-
> > > 05491-g5d066766c5f1 #0
> > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > > Google 09/13/2024
> > > Workqueue: infiniband ib_cache_event_task
> > > Call Trace:
> > > <TASK>
> > > __dump_stack lib/dump_stack.c:94 [inline]
> > > dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
> > > print_address_description mm/kasan/report.c:377 [inline]
> > > print_report+0x169/0x550 mm/kasan/report.c:488
> > > kasan_report+0x143/0x180 mm/kasan/report.c:601
> > > siw_query_port+0x348/0x440 drivers/infiniband/sw/siw/siw_verbs.c:183
> > > ib_cache_update+0x1a9/0xb80 drivers/infiniband/core/cache.c:1494
> > > ib_cache_event_task+0xf3/0x1e0 drivers/infiniband/core/cache.c:1568
> > > process_one_work kernel/workqueue.c:3229 [inline]
> > > process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
> > > worker_thread+0x870/0xd30 kernel/workqueue.c:3391
> > > kthread+0x2f0/0x390 kernel/kthread.c:389
> > > ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
> > > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
> > > </TASK>
> > >
> >
> > Here siw is getting a use-after-free when accessing the netdev in
> > query_port() verb, since the netdev got free'd already. I was
> > assuming the rdma core would serialize device deallocation
> > and driver access accordingly. Seems not to be the case?
>
> I would say that SIW/RXE should be converted from direct store and access
> of sdev->netdev in favor of ib_device_get_netdev() and in
> ib_unregister_device_queued()
> needs to see something like that ib_device_set_netdev(..., NULL, ...);
>

Makes sense. There is no good reason to keep the netdev
pointer around in the driver, even worse without having
a hold on it.

From netdev siw only needs MTU and ifindex information. I assume
netdev's ifindex will not change (?), and MTU changes can be
captured in the netdev notifier upcall. So probably simplest
to just keep that information around in the driver - MTU to
satisfy query_port(), query_qp() and restrict wildcard listen
calls to the current device (ifindex needed here).

Thanks,
Bernard.

> Thanks