linux-kernel - Re: [syzbot] KASAN: use-after-free Read in snd_rawmidi

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Date:   Fri, 13 Jan 2023 04:32:18 -0800
From:   syzbot <syzbot+e3ec01fd2d18c9264c3b@...kaller.appspotmail.com>
To:     hdanton@...a.com, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] KASAN: use-after-free Read in snd_rawmidi_poll

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING: refcount bug in mm_update_next_owner

------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 0 PID: 5598 at lib/refcount.c:25 refcount_warn_saturate+0x17c/0x1f0 lib/refcount.c:25
Modules linked in:
CPU: 0 PID: 5598 Comm: syz-executor.0 Not tainted 6.2.0-rc3-next-20230112-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
RIP: 0010:refcount_warn_saturate+0x17c/0x1f0 lib/refcount.c:25
Code: 0a 31 ff 89 de e8 d4 13 78 fd 84 db 0f 85 2e ff ff ff e8 57 17 78 fd 48 c7 c7 60 87 a6 8a c6 05 60 d0 54 0a 01 e8 98 a7 b2 05 <0f> 0b e9 0f ff ff ff e8 38 17 78 fd 0f b6 1d 4a d0 54 0a 31 ff 89
RSP: 0018:ffffc90005befb68 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88807d2f57c0 RSI: ffffffff8166972c RDI: fffff52000b7df5f
RBP: ffff88807d2f3aa8 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff8880764ee300
R13: ffff88807d2f3fa8 R14: 0000000000000000 R15: ffff88807d2f3aa8
FS:  0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000021000000 CR3: 000000007673f000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __refcount_add include/linux/refcount.h:199 [inline]
 __refcount_inc include/linux/refcount.h:250 [inline]
 refcount_inc include/linux/refcount.h:267 [inline]
 get_task_struct include/linux/sched/task.h:110 [inline]
 mm_update_next_owner+0x585/0x7b0 kernel/exit.c:504
 exit_mm kernel/exit.c:562 [inline]
 do_exit+0x9a4/0x2a90 kernel/exit.c:854
 do_group_exit+0xd4/0x2a0 kernel/exit.c:1012
 get_signal+0x225f/0x24f0 kernel/signal.c:2859
 arch_do_signal_or_restart+0x79/0x5c0 arch/x86/kernel/signal.c:306
 exit_to_user_mode_loop kernel/entry/common.c:168 [inline]
 exit_to_user_mode_prepare+0x11f/0x240 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
 syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:297
 do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f9d6f48c0c9
Code: Unable to access opcode bytes at 0x7f9d6f48c09f.
RSP: 002b:00007f9d70279218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f9d6f5abf88 RCX: 00007f9d6f48c0c9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f9d6f5abf88
RBP: 00007f9d6f5abf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f9d6f5abf8c
R13: 00007ffd0405f78f R14: 00007f9d70279300 R15: 0000000000022000
 </TASK>


Tested on:

commit:         0a093b28 Add linux-next specific files for 20230112
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=116f295a480000
kernel config:  https://syzkaller.appspot.com/x/.config?x=835f3591019836d5
dashboard link: https://syzkaller.appspot.com/bug?extid=e3ec01fd2d18c9264c3b
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=104b995a480000