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 74D672192F4; Mon, 18 Aug 2025 13:49:43 +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=1755524986; cv=none; b=Q8XvheK6vTKkVBh3hLt0VCC/OQDh1MT5fGLQNgqMz0MJCidQUX8tbI9ieXJrjpNfB+me3elkpTzo8lxL48oqu/uHFfcsjR+ZOeGCu8xt/5HLocoqsnK90aAjv3z1SOyJZGdv1XWxUJNNiNKKWdkCnsllZt4xaYE5SB3lO9VW19w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755524986; c=relaxed/simple; bh=LV+zhdbyyEIYjj0nARVB8R+2AH6pHyLPKHDXfrn4wjM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=rZfPwdsRQD4UB2YPx06kQivO+h+5Tntn6u9vn7Xg7E/+Qmq4Pea6uuoNhXnmImJpXaKG56paacCybiaPEObw+OjeZv+HKfaogWSj9zieMtUv7Ck7M1fBtzRE9Pzxts12dYF8r7kv6OCK/eO3KwX0u1UtMe8pmBWrmJmW6b7iZFo= 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 [10.17.112.211] (unknown [15.248.3.83]) by plesk.hostmyservers.fr (Postfix) with ESMTPSA id 644AB40B1F; Mon, 18 Aug 2025 13:49:35 +0000 (UTC) Authentication-Results: Plesk; spf=pass (sender IP is 15.248.3.83) smtp.mailfrom=contact@arnaud-lcm.com smtp.helo=[10.17.112.211] Received-SPF: pass (Plesk: connection is authenticated) Message-ID: <07d849b2-67c2-40b2-9cd3-75b8f3a4e0a6@arnaud-lcm.com> Date: Mon, 18 Aug 2025 14:49:34 +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-next v4 2/2] bpf: fix stackmap overflow check in __bpf_get_stackid() To: song@kernel.org, jolsa@kernel.org Cc: andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, haoluo@google.com, john.fastabend@gmail.com, jolsa@kernel.org, kpsingh@kernel.org, linux-kernel@vger.kernel.org, martin.lau@linux.dev, sdf@fomichev.me, song@kernel.org, syzbot+c9b724fbb41cf2538b7b@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com, yonghong.song@linux.dev References: <20250813204606.167019-1-contact@arnaud-lcm.com> <20250813205506.168069-1-contact@arnaud-lcm.com> Content-Language: en-US From: "Lecomte, Arnaud" In-Reply-To: <20250813205506.168069-1-contact@arnaud-lcm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-PPP-Message-ID: <175552497619.9428.7858426650122712005@Plesk> X-PPP-Vhost: arnaud-lcm.com Hey, Just forwarding the patch to the associated maintainers with `stackmap.c`. 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@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=c9b724fbb41cf2538b7b > Signed-off-by: Arnaud Lecomte > --- > kernel/bpf/stackmap.c | 23 +++++++++++++---------- > 1 file changed, 13 insertions(+), 10 deletions(-) > > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > index b9cc6c72a2a5..318f150460bb 100644 > --- a/kernel/bpf/stackmap.c > +++ b/kernel/bpf/stackmap.c > @@ -246,7 +246,7 @@ get_callchain_entry_for_task(struct task_struct *task, u32 max_depth) > } > > static long __bpf_get_stackid(struct bpf_map *map, > - struct perf_callchain_entry *trace, u64 flags) > + struct perf_callchain_entry *trace, u64 flags, u32 max_depth) > { > struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); > struct stack_map_bucket *bucket, *new_bucket, *old_bucket; > @@ -262,6 +262,8 @@ static long __bpf_get_stackid(struct bpf_map *map, > > trace_nr = trace->nr - skip; > trace_len = trace_nr * sizeof(u64); > + trace_nr = min(trace_nr, max_depth - skip); > + > ips = trace->ip + skip; > hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0); > id = hash & (smap->n_buckets - 1); > @@ -321,19 +323,17 @@ static long __bpf_get_stackid(struct bpf_map *map, > BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, > u64, flags) > { > - u32 max_depth = map->value_size / stack_map_data_size(map); > - u32 skip = flags & BPF_F_SKIP_FIELD_MASK; > + u32 elem_size = stack_map_data_size(map); > bool user = flags & BPF_F_USER_STACK; > struct perf_callchain_entry *trace; > bool kernel = !user; > + u32 max_depth; > > if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | > BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) > return -EINVAL; > > - max_depth += skip; > - if (max_depth > sysctl_perf_event_max_stack) > - max_depth = sysctl_perf_event_max_stack; > + max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags); > > trace = get_perf_callchain(regs, 0, kernel, user, max_depth, > false, false); > @@ -342,7 +342,7 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, > /* couldn't fetch the stack trace */ > return -EFAULT; > > - return __bpf_get_stackid(map, trace, flags); > + return __bpf_get_stackid(map, trace, flags, max_depth); > } > > const struct bpf_func_proto bpf_get_stackid_proto = { > @@ -374,6 +374,7 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, > bool kernel, user; > __u64 nr_kernel; > int ret; > + u32 elem_size, max_depth; > > /* perf_sample_data doesn't have callchain, use bpf_get_stackid */ > if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)) > @@ -392,12 +393,13 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, > return -EFAULT; > > nr_kernel = count_kernel_ip(trace); > - > + elem_size = stack_map_data_size(map); > if (kernel) { > __u64 nr = trace->nr; > > trace->nr = nr_kernel; > - ret = __bpf_get_stackid(map, trace, flags); > + max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags); > + ret = __bpf_get_stackid(map, trace, flags, max_depth); > > /* restore nr */ > trace->nr = nr; > @@ -409,7 +411,8 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, > return -EFAULT; > > flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip; > - ret = __bpf_get_stackid(map, trace, flags); > + max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags); > + ret = __bpf_get_stackid(map, trace, flags, max_depth); > } > return ret; > }