netdev - Re: [PATCH v1 can] can: bcm: Clear bo->bcm_proc_read after remove_proc

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Message-ID: <CAMZ6RqLHbxdda_CLg-_N-WN8zxjWOaDQ2qOck8-Xj-6Myjh1Qg@mail.gmail.com>
Date: Thu, 5 Sep 2024 10:30:26 +0900
From: Vincent MAILHOL <mailhol.vincent@...adoo.fr>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: Oliver Hartkopp <socketcan@...tkopp.net>, Marc Kleine-Budde <mkl@...gutronix.de>, 
	Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org, linux-can@...r.kernel.org, 
	syzbot+0532ac7a06fb1a03187e@...kaller.appspotmail.com
Subject: Re: [PATCH v1 can] can: bcm: Clear bo->bcm_proc_read after remove_proc_entry().

Hi Iwashima san,

Thank you for your patch.

On Thu. 5 Sep. 2024 at 10:24, Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
> syzbot reported a warning in bcm_release(). [0]
>
> The blamed change fixed another warning that is triggered when
> connect() is issued again for a socket whose connect()ed device has
> been unregistered.
>
> However, if the socket is just close()d without the 2nd connect(), the
> remaining bo->bcm_proc_read triggers unnecessary remove_proc_entry()
> in bcm_release().
>
> Let's clear bo->bcm_proc_read after remove_proc_entry() in bcm_notify().
>
> [0]
> name '4986'
> WARNING: CPU: 0 PID: 5234 at fs/proc/generic.c:711 remove_proc_entry+0x2e7/0x5d0 fs/proc/generic.c:711
> Modules linked in:
> CPU: 0 UID: 0 PID: 5234 Comm: syz-executor606 Not tainted 6.11.0-rc5-syzkaller-00178-g5517ae241919 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
> RIP: 0010:remove_proc_entry+0x2e7/0x5d0 fs/proc/generic.c:711
> Code: ff eb 05 e8 cb 1e 5e ff 48 8b 5c 24 10 48 c7 c7 e0 f7 aa 8e e8 2a 38 8e 09 90 48 c7 c7 60 3a 1b 8c 48 89 de e8 da 42 20 ff 90 <0f> 0b 90 90 48 8b 44 24 18 48 c7 44 24 40 0e 36 e0 45 49 c7 04 07
> RSP: 0018:ffffc9000345fa20 EFLAGS: 00010246
> RAX: 2a2d0aee2eb64600 RBX: ffff888032f1f548 RCX: ffff888029431e00
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: ffffc9000345fb08 R08: ffffffff8155b2f2 R09: 1ffff1101710519a
> R10: dffffc0000000000 R11: ffffed101710519b R12: ffff888011d38640
> R13: 0000000000000004 R14: 0000000000000000 R15: dffffc0000000000
> FS:  0000000000000000(0000) GS:ffff8880b8800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fcfb52722f0 CR3: 000000000e734000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  bcm_release+0x250/0x880 net/can/bcm.c:1578
>  __sock_release net/socket.c:659 [inline]
>  sock_close+0xbc/0x240 net/socket.c:1421
>  __fput+0x24a/0x8a0 fs/file_table.c:422
>  task_work_run+0x24f/0x310 kernel/task_work.c:228
>  exit_task_work include/linux/task_work.h:40 [inline]
>  do_exit+0xa2f/0x27f0 kernel/exit.c:882
>  do_group_exit+0x207/0x2c0 kernel/exit.c:1031
>  __do_sys_exit_group kernel/exit.c:1042 [inline]
>  __se_sys_exit_group kernel/exit.c:1040 [inline]
>  __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1040
>  x64_sys_call+0x2634/0x2640 arch/x86/include/generated/asm/syscalls_64.h:232
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fcfb51ee969
> Code: Unable to access opcode bytes at 0x7fcfb51ee93f.
> RSP: 002b:00007ffce0109ca8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fcfb51ee969
> RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000001
> RBP: 00007fcfb526f3b0 R08: ffffffffffffffb8 R09: 0000555500000000
> R10: 0000555500000000 R11: 0000000000000246 R12: 00007fcfb526f3b0
> R13: 0000000000000000 R14: 00007fcfb5271ee0 R15: 00007fcfb51bf160
>  </TASK>
>
> Fixes: 76fe372ccb81 ("can: bcm: Remove proc entry when dev is unregistered.")
> Reported-by: syzbot+0532ac7a06fb1a03187e@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=0532ac7a06fb1a03187e
> Tested-by: syzbot+0532ac7a06fb1a03187e@...kaller.appspotmail.com
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>

Reviewed-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>