linux-kernel - Re: [PATCH bpf-next v4 2/2] bpf: fix stackmap overflow check in __bpf_get

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Message-ID: <ca5b2f4a-f92d-4749-9abe-c2af9254addc@linux.dev>
Date: Mon, 18 Aug 2025 09:57:58 -0700
From: Yonghong Song <yonghong.song@...ux.dev>
To: "Lecomte, Arnaud" <contact@...aud-lcm.com>, song@...nel.org,
 jolsa@...nel.org
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
 daniel@...earbox.net, eddyz87@...il.com, haoluo@...gle.com,
 john.fastabend@...il.com, kpsingh@...nel.org, linux-kernel@...r.kernel.org,
 martin.lau@...ux.dev, sdf@...ichev.me,
 syzbot+c9b724fbb41cf2538b7b@...kaller.appspotmail.com,
 syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH bpf-next v4 2/2] bpf: fix stackmap overflow check in
 __bpf_get_stackid()



On 8/18/25 6:49 AM, Lecomte, Arnaud wrote:
> Hey,
> Just forwarding the patch to the associated maintainers with 
> `stackmap.c`.

Arnaud, please add Ack (provided in comments for v3) to make things easier
for maintainers.

Also, looks like all your patch sets (v1 to v4) in the same thread.
It would be good to have all these versions in separate thread.
Please look at some examples in bpf mailing list.

> Have a great day,
> Cheers
>
> On 13/08/2025 21:55, Arnaud Lecomte wrote:
>> Syzkaller reported a KASAN slab-out-of-bounds write in 
>> __bpf_get_stackid()
>> when copying stack trace data. The issue occurs when the perf trace
>>   contains more stack entries than the stack map bucket can hold,
>>   leading to an out-of-bounds write in the bucket's data array.
>>
>> Changes in v2:
>>   - Fixed max_depth names across get stack id
>>
>> Changes in v4:
>>   - Removed unnecessary empty line in __bpf_get_stackid
>>
>> Reported-by: syzbot+c9b724fbb41cf2538b7b@...kaller.appspotmail.com
>> Closes: https://syzkaller.appspot.com/bug?extid=c9b724fbb41cf2538b7b
>> Signed-off-by: Arnaud Lecomte <contact@...aud-lcm.com>
>> ---
>>   kernel/bpf/stackmap.c | 23 +++++++++++++----------
>>   1 file changed, 13 insertions(+), 10 deletions(-)
>>
[...]