Subject: Re: [PATCH net v5 2/2] net: sched: use RCU read-side critical section in taprio_dump()

From: Vinicius Costa Gomes <[email-masked]>
Date: Thu, 05 Sep 2024 09:44:32 -0300

Dmitry Antipov <[email-masked]> writes:

> Fix possible use-after-free in 'taprio_dump()' by adding RCU
> read-side critical section there. Never seen on x86 but
> found on a KASAN-enabled arm64 system when investigating
> https://syzkaller.appspot.com/bug?extid=b65e0af58423fc8a73aa:
>
> [T15862] BUG: KASAN: slab-use-after-free in taprio_dump+0xa0c/0xbb0
> [T15862] Read of size 4 at addr ffff0000d4bb88f8 by task repro/15862
> [T15862]
> [T15862] CPU: 0 UID: 0 PID: 15862 Comm: repro Not tainted 6.11.0-rc1-00293-gdefaf1a2113a-dirty #2
> [T15862] Hardware name: QEMU QEMU Virtual Machine, BIOS edk2-20240524-5.fc40 05/24/2024
> [T15862] Call trace:
> [T15862]  dump_backtrace+0x20c/0x220
> [T15862]  show_stack+0x2c/0x40
> [T15862]  dump_stack_lvl+0xf8/0x174
> [T15862]  print_report+0x170/0x4d8
> [T15862]  kasan_report+0xb8/0x1d4
> [T15862]  __asan_report_load4_noabort+0x20/0x2c
> [T15862]  taprio_dump+0xa0c/0xbb0
> [T15862]  tc_fill_qdisc+0x540/0x1020
> [T15862]  qdisc_notify.isra.0+0x330/0x3a0
> [T15862]  tc_modify_qdisc+0x7b8/0x1838
> [T15862]  rtnetlink_rcv_msg+0x3c8/0xc20
> [T15862]  netlink_rcv_skb+0x1f8/0x3d4
> [T15862]  rtnetlink_rcv+0x28/0x40
> [T15862]  netlink_unicast+0x51c/0x790
> [T15862]  netlink_sendmsg+0x79c/0xc20
> [T15862]  __sock_sendmsg+0xe0/0x1a0
> [T15862]  ____sys_sendmsg+0x6c0/0x840
> [T15862]  ___sys_sendmsg+0x1ac/0x1f0
> [T15862]  __sys_sendmsg+0x110/0x1d0
> [T15862]  __arm64_sys_sendmsg+0x74/0xb0
> [T15862]  invoke_syscall+0x88/0x2e0
> [T15862]  el0_svc_common.constprop.0+0xe4/0x2a0
> [T15862]  do_el0_svc+0x44/0x60
> [T15862]  el0_svc+0x50/0x184
> [T15862]  el0t_64_sync_handler+0x120/0x12c
> [T15862]  el0t_64_sync+0x190/0x194
> [T15862]
> [T15862] Allocated by task 15857:
> [T15862]  kasan_save_stack+0x3c/0x70
> [T15862]  kasan_save_track+0x20/0x3c
> [T15862]  kasan_save_alloc_info+0x40/0x60
> [T15862]  __kasan_kmalloc+0xd4/0xe0
> [T15862]  __kmalloc_cache_noprof+0x194/0x334
> [T15862]  taprio_change+0x45c/0x2fe0
> [T15862]  tc_modify_qdisc+0x6a8/0x1838
> [T15862]  rtnetlink_rcv_msg+0x3c8/0xc20
> [T15862]  netlink_rcv_skb+0x1f8/0x3d4
> [T15862]  rtnetlink_rcv+0x28/0x40
> [T15862]  netlink_unicast+0x51c/0x790
> [T15862]  netlink_sendmsg+0x79c/0xc20
> [T15862]  __sock_sendmsg+0xe0/0x1a0
> [T15862]  ____sys_sendmsg+0x6c0/0x840
> [T15862]  ___sys_sendmsg+0x1ac/0x1f0
> [T15862]  __sys_sendmsg+0x110/0x1d0
> [T15862]  __arm64_sys_sendmsg+0x74/0xb0
> [T15862]  invoke_syscall+0x88/0x2e0
> [T15862]  el0_svc_common.constprop.0+0xe4/0x2a0
> [T15862]  do_el0_svc+0x44/0x60
> [T15862]  el0_svc+0x50/0x184
> [T15862]  el0t_64_sync_handler+0x120/0x12c
> [T15862]  el0t_64_sync+0x190/0x194
> [T15862]
> [T15862] Freed by task 6192:
> [T15862]  kasan_save_stack+0x3c/0x70
> [T15862]  kasan_save_track+0x20/0x3c
> [T15862]  kasan_save_free_info+0x4c/0x80
> [T15862]  poison_slab_object+0x110/0x160
> [T15862]  __kasan_slab_free+0x3c/0x74
> [T15862]  kfree+0x134/0x3c0
> [T15862]  taprio_free_sched_cb+0x18c/0x220
> [T15862]  rcu_core+0x920/0x1b7c
> [T15862]  rcu_core_si+0x10/0x1c
> [T15862]  handle_softirqs+0x2e8/0xd64
> [T15862]  __do_softirq+0x14/0x20
>
> Fixes: 18cdd2f0998a ("net/sched: taprio: taprio_dump and taprio_change are protected by rtnl_mutex")
> Signed-off-by: Dmitry Antipov <[email-masked]>
> ---
> v5: add Fixes: and resend due to series change
> v4: redesign to preserve original code as much as possible,
>     adjust commit message and subject to target net tree
> v3: tweak commit message as suggested by Vinicius
> v2: added to the series
> ---

Acked-by: Vinicius Costa Gomes <[email-masked]>

Cheers,
-- 
Vinicius