New subject: Bug: slab-out-of-bounds in snd_seq_oss_synth_sysex

28 Dec 2024


      ...
...
2024年12月25日 13:37，Kun Hu huk23@m.fudan.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@m.fudan.edu.cn
—————
Thanks,
Kun Hu
...
2024年12月24日 19:16，Kun Hu huk23@m.fudan.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=s...
Kernel config: https://drive.google.com/file/d/1RhT5dFTs6Vx1U71PbpenN7TPtnPoa3NI/view?usp=s...
C reproducer: https://drive.google.com/file/d/177HJht6a7-6F3YLudKb_d4kiPGd1VA_i/view?usp=s...
Syzlang reproducer: https://drive.google.com/file/d/1AuP5UGGc47rEXXPuvjmCKgJ3d0U1P84j/view?usp=s...
If you fix this issue, please add the following tag to the commit:
Reported-by: Kun Hu huk23@m.fudan.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

Re: Bug: slab-out-of-bounds in snd_seq_oss_synth_sysex