Re: [PATCH] Bluetooth: hci_core: fix suspicious RCU usage in hci_conn_drop()

[Simon Horman]

+ Handa-san

On Wed, Jul 24, 2024 at 02:17:57AM +0900, Yunseong Kim wrote:
> Protection from the queuing operation is achieved with an RCU read lock
> to avoid calling 'queue_delayed_work()' after 'cancel_delayed_work()',
> but this does not apply to 'hci_conn_drop()'.
> 
> commit deee93d13d38 ("Bluetooth: use hdev->workqueue when queuing
>  hdev->{cmd,ncmd}_timer works")
> 
> The situation described raises concerns about suspicious RCU usage in a
> corrupted context.
> 
> CPU 1                   CPU 2
>  hci_dev_do_reset()
>   synchronize_rcu()      hci_conn_drop()
>   drain_workqueue()       <-- no RCU read protection during queuing. -->
>                            queue_delayed_work()
> 
> It displays a warning message like the following
> 
> Bluetooth: hci0: unexpected cc 0x0c38 length: 249 > 2
> =============================
> WARNING: suspicious RCU usage
> 6.10.0-rc6-01340-gf14c0bb78769 #5 Not tainted
> -----------------------------
> net/mac80211/util.c:4000 RCU-list traversed in non-reader section!!
> 
> other info that might help us debug this:
> 
> rcu_scheduler_active = 2, debug_locks = 1
> 2 locks held by syz-executor/798:
>  #0: ffff800089a3de50 (rtnl_mutex){+.+.}-{4:4},
>     at: rtnl_lock+0x28/0x40 net/core/rtnetlink.c:79
> 
> stack backtrace:
> CPU: 0 PID: 798 Comm: syz-executor Not tainted
>   6.10.0-rc6-01340-gf14c0bb78769 #5
> Hardware name: linux,dummy-virt (DT)
> Call trace:
>  dump_backtrace.part.0+0x1b8/0x1d0 arch/arm64/kernel/stacktrace.c:317
>  dump_backtrace arch/arm64/kernel/stacktrace.c:323 [inline]
>  show_stack+0x34/0x50 arch/arm64/kernel/stacktrace.c:324
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0xf0/0x170 lib/dump_stack.c:114
>  dump_stack+0x20/0x30 lib/dump_stack.c:123
>  lockdep_rcu_suspicious+0x204/0x2f8 kernel/locking/lockdep.c:6712
>  ieee80211_check_combinations+0x71c/0x828 [mac80211]
>  ieee80211_check_concurrent_iface+0x494/0x700 [mac80211]
>  ieee80211_open+0x140/0x238 [mac80211]
>  __dev_open+0x270/0x498 net/core/dev.c:1474
>  __dev_change_flags+0x47c/0x610 net/core/dev.c:8837
>  dev_change_flags+0x98/0x170 net/core/dev.c:8909
>  devinet_ioctl+0xdf0/0x18d0 net/ipv4/devinet.c:1177
>  inet_ioctl+0x34c/0x388 net/ipv4/af_inet.c:1003
>  sock_do_ioctl+0xe4/0x240 net/socket.c:1222
>  sock_ioctl+0x4cc/0x740 net/socket.c:1341
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:907 [inline]
>  __se_sys_ioctl fs/ioctl.c:893 [inline]
>  __arm64_sys_ioctl+0x184/0x218 fs/ioctl.c:893
>  __invoke_syscall arch/arm64/kernel/syscall.c:34 [inline]
>  invoke_syscall+0x90/0x2e8 arch/arm64/kernel/syscall.c:48
>  el0_svc_common.constprop.0+0x200/0x2a8 arch/arm64/kernel/syscall.c:131
>  el0_svc+0x48/0xc0 arch/arm64/kernel/entry-common.c:712
>  el0t_64_sync_handler+0x120/0x130 arch/arm64/kernel/entry-common.c:730
>  el0t_64_sync+0x190/0x198 arch/arm64/kernel/entry.S:598
> 
> This patch attempts to fix that issue with the same convention.
> 
> Cc: stable@xxxxxxxxxxxxxxx # v6.1+
> Fixes: deee93d13d38 ("Bluetooth: use hdev->workqueue when queuing hdev->
> {cmd,ncmd}_timer works")

nit: Fixes tags should not be line-wrapped.

> Signed-off-by: Yeoreum Yun <yeoreum.yun@xxxxxxx>
> Tested-by: Yunseong Kim <yskelg@xxxxxxxxx>
> Signed-off-by: Yunseong Kim <yskelg@xxxxxxxxx>

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