linux-kernel - Re: Bug: slab-out-of-bounds in snd_seq_oss_synth

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Message-Id: <13599E88-AAF1-4621-94BE-C621677D9298@m.fudan.edu.cn>
Date: Sat, 28 Dec 2024 16:07:16 +0800
From: Kun Hu <huk23@...udan.edu.cn>
To: perex@...ex.cz,
 tiwai@...e.com,
 vkoul@...nel.org,
 lars@...afoo.de,
 broonie@...nel.org,
 Liam Girdwood <lgirdwood@...il.com>,
 masahiroy@...nel.org,
 andriy.shevchenko@...ux.intel.com,
 arnd@...db.de,
 yuehaibing@...wei.com,
 viro@...iv.linux.org.uk,
 dmantipov@...dex.ru
Cc: linux-sound@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 "jjtan24@...udan.edu.cn" <jjtan24@...udan.edu.cn>,
 stable@...r.kernel.org
Subject: Re: Bug: slab-out-of-bounds in snd_seq_oss_synth_sysex

> 
> 
>> 2024年12月25日 13:37，Kun Hu <huk23@...udan.edu.cn> 写道：
>> 
>> Hello,
>> 
>>> BUG: KASAN: slab-out-of-bounds in snd_seq_oss_synth_sysex+0x5d1/0x6c0 sound/core/seq/oss/seq_oss_synth.c:516
>> 
>> We further analyzed the issue at line 516 in ./sound/core/seq/oss/seq_oss_synth.c. 
>> The slab-out-of-bounds crash occurs in line 509, when sysex->len = 128. Specifically, the write operation to dest[0] accesses memory beyond the bounds of sysex->buf (128 byte).
>> To resolve this issue, we suggest adding 6 lines of code to validate the legality of the address write to sysex->buf before entering the loop:
>> 
>> if (sysex->len >= MAX_SYSEX_BUFLEN) { 
>>  sysex->len = 0; 
>>  sysex->skip = 1; 
>>  return -EINVAL;  /* Exit early if sysex->len is out of bounds */ 
>> }
>> 
>> If you fix this issue, please add the following tag to the commit:
>> Reported-by: Kun Hu <huk23@...udan.edu.cn>
>> 
>> —————
>> Thanks,
>> Kun Hu
>> 
>>> 2024年12月24日 19:16，Kun Hu <huk23@...udan.edu.cn> 写道：
>>> 
>>> Hello,
>>> 
>>> When using fuzzer tool to fuzz the latest Linux kernel, the following crash
>>> was triggered.
>>> 
>>> HEAD commit: 78d4f34e2115b517bcbfe7ec0d018bbbb6f9b0b8
>>> git tree: upstream
>>> Console output:https://drive.google.com/file/d/17oCyKDW_kNhSW5Bbvm23vnpD1eo0MHFi/view?usp=sharing
>>> Kernel config: https://drive.google.com/file/d/1RhT5dFTs6Vx1U71PbpenN7TPtnPoa3NI/view?usp=sharing
>>> C reproducer: https://drive.google.com/file/d/177HJht6a7-6F3YLudKb_d4kiPGd1VA_i/view?usp=sharing
>>> Syzlang reproducer: https://drive.google.com/file/d/1AuP5UGGc47rEXXPuvjmCKgJ3d0U1P84j/view?usp=sharing
>>> 
>>> 
>>> If you fix this issue, please add the following tag to the commit:
>>> Reported-by: Kun Hu <huk23@...udan.edu.cn>
>>> 
>>> ==================================================================
>>> BUG: KASAN: slab-out-of-bounds in snd_seq_oss_synth_sysex+0x5d1/0x6c0 sound/core/seq/oss/seq_oss_synth.c:516
>>> Write of size 1 at addr ff1100000588e288 by task syz-executor411/824
>>> 
>>> CPU: 2 UID: 0 PID: 824 Comm: syz-executor411 Not tainted 6.13.0-rc3 #5
>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
>>> Call Trace:
>>> <TASK>
>>> __dump_stack lib/dump_stack.c:94 [inline]
>>> dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
>>> print_address_description mm/kasan/report.c:378 [inline]
>>> print_report+0xcf/0x5f0 mm/kasan/report.c:489
>>> kasan_report+0x93/0xc0 mm/kasan/report.c:602
>>> snd_seq_oss_synth_sysex+0x5d1/0x6c0 sound/core/seq/oss/seq_oss_synth.c:516
>>> snd_seq_oss_process_event+0x46a/0x2620 sound/core/seq/oss/seq_oss_event.c:61
>>> insert_queue sound/core/seq/oss/seq_oss_rw.c:167 [inline]
>>> snd_seq_oss_write+0x261/0x7f0 sound/core/seq/oss/seq_oss_rw.c:135
>>> odev_write+0x53/0xa0 sound/core/seq/oss/seq_oss.c:168
>>> vfs_write fs/read_write.c:677 [inline]
>>> vfs_write+0x2e3/0x10f0 fs/read_write.c:659
>>> ksys_write+0x122/0x240 fs/read_write.c:731
>>> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>>> do_syscall_64+0xc3/0x1d0 arch/x86/entry/common.c:83
>>> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>> 
> 

Hello, 

Is this issue being considered and is it possible that the value of sysex->len in line 509 of the snd_seq_oss_synth_sysex function could exceed 127 and thus be out of bounds?

———
Best Regards,
Kun Hu