From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from plesk.hostmyservers.fr (plesk.hostmyservers.fr [45.145.164.37]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CBD3534CF5; Tue, 29 Jul 2025 16:54:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.145.164.37 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753808095; cv=none; b=BkE1A3aqXthE62b65zsBOF+vJE2oGcb8RwQV7Ki7tP128FJJlqRRDg32CsXMS9T9juF6XdY39wKNhTt330avPv48Ev/Nr8hFNeOw2MJ7J/hKt2HG3Aa9xruVAr4G/AOssWvZIDNm9y+Vg/ZKLaKiCxb5ESpjj8UOUHe3wCyNua8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753808095; c=relaxed/simple; bh=U1cCvd6q1MNbUiSScV1UzAwX6zIHoAjp0LdgULFE0Fs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=i9xLGIbsbYqUTpSqVlWqSGxknSxhy3QIlJ1KMLHJ1aHO+J7VE5g6Pp4pRotyQVhL0ds1Sh/t/PNKFCj6TSmTgeCTi+DZULclGGRi4G+4rSIcgqaffpSJ9Q5PMbPon4iczWBXMyQeH44QplVWEaadb5YdW7g+l4Sj3/MZTowjnjU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=arnaud-lcm.com; spf=pass smtp.mailfrom=arnaud-lcm.com; arc=none smtp.client-ip=45.145.164.37 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=arnaud-lcm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arnaud-lcm.com Received: from [IPV6:2a02:8084:255b:aa00:d071:2bab:ab9:4510] (unknown [IPv6:2a02:8084:255b:aa00:d071:2bab:ab9:4510]) by plesk.hostmyservers.fr (Postfix) with ESMTPSA id EDD4D40B15; Tue, 29 Jul 2025 16:54:49 +0000 (UTC) Authentication-Results: Plesk; spf=pass (sender IP is 2a02:8084:255b:aa00:d071:2bab:ab9:4510) smtp.mailfrom=contact@arnaud-lcm.com smtp.helo=[IPV6:2a02:8084:255b:aa00:d071:2bab:ab9:4510] Received-SPF: pass (Plesk: connection is authenticated) Message-ID: Date: Tue, 29 Jul 2025 17:54:45 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] bpf: fix stackmap overflow check in __bpf_get_stackid() To: Yonghong Song , song@kernel.org Cc: jolsa@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+c9b724fbb41cf2538b7b@syzkaller.appspotmail.com References: <20250729091901.26436-1-contact@arnaud-lcm.com> <004ec202-cbe7-4108-b6ac-1d947a5a54b8@linux.dev> Content-Language: en-US From: Arnaud Lecomte In-Reply-To: <004ec202-cbe7-4108-b6ac-1d947a5a54b8@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-PPP-Message-ID: <175380809082.17798.6177797408058807626@Plesk> X-PPP-Vhost: arnaud-lcm.com Good catch thanks Yonghong, sending rev2. On 29/07/2025 17:21, Yonghong Song wrote: > > > On 7/29/25 2:19 AM, 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. >> For build_id mode, we use sizeof(struct bpf_stack_build_id) >>   to determine capacity, and for normal mode we use sizeof(u64). >> >> Reported-by: syzbot+c9b724fbb41cf2538b7b@syzkaller.appspotmail.com >> Closes: https://syzkaller.appspot.com/bug?extid=c9b724fbb41cf2538b7b >> Tested-by: syzbot+c9b724fbb41cf2538b7b@syzkaller.appspotmail.com >> Signed-off-by: Arnaud Lecomte >> --- >>   kernel/bpf/stackmap.c | 12 +++++++++++- >>   1 file changed, 11 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c >> index 3615c06b7dfa..0f9f6e4b6fe9 100644 >> --- a/kernel/bpf/stackmap.c >> +++ b/kernel/bpf/stackmap.c >> @@ -230,7 +230,7 @@ static long __bpf_get_stackid(struct bpf_map *map, >>       struct bpf_stack_map *smap = container_of(map, struct >> bpf_stack_map, map); >>       struct stack_map_bucket *bucket, *new_bucket, *old_bucket; >>       u32 skip = flags & BPF_F_SKIP_FIELD_MASK; >> -    u32 hash, id, trace_nr, trace_len, i; >> +    u32 hash, id, trace_nr, trace_len, i, max_depth; >>       bool user = flags & BPF_F_USER_STACK; >>       u64 *ips; >>       bool hash_matches; >> @@ -241,6 +241,16 @@ static long __bpf_get_stackid(struct bpf_map *map, >>         trace_nr = trace->nr - skip; >>       trace_len = trace_nr * sizeof(u64); >> + >> +    /* Clamp the trace to max allowed depth */ >> +    if (stack_map_use_build_id(map)) >> +        max_depth = smap->map.value_size / sizeof(struct >> bpf_stack_build_id); >> +    else >> +        max_depth = smap->map.value_size / sizeof(u64); > > Replace the above with >     max_depth = smap->map.value_size / stack_map_data_size(map) > ? > >> + >> +    if (trace_nr > max_depth) >> +        trace_nr = max_depth; >> + >>       ips = trace->ip + skip; >>       hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0); >>       id = hash & (smap->n_buckets - 1); > >