From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-172.mta0.migadu.com (out-172.mta0.migadu.com [91.218.175.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EA9E32BE640 for ; Wed, 13 Aug 2025 06:00:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755064804; cv=none; b=sTRPRr4aaILqAClpT78toSqgEl43WVyq6ftyy2YyPFak7x8IftLu9uYBWHQUWk2PMNMFLw43sjr5casTxkJeStLPQ1prAUPe1RTW8qWXPsp5x4LncSzMfy06Mo8KXvQVd5Yp7BN7Wj7NybDJGy/8j98RzLstd9PebG/qEY5MlNw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755064804; c=relaxed/simple; bh=JF9fdZsv+ShJc346su7lt6oncbiLbBV/jASjYgXa4yA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=t/0JN2D+i3YBe787yAcUru2fOjUUAxKutpFjEHsrtKEG5+7rgBBl2JYJV8UiRK5UJrxI69FbUoMpIdzLhPQcUjioxkyV+fjVzx3c2fE8/SpS3ESwkcGsbjy9XLQ+7vaILlA1hzeOq8hjRH7z6T0wRuY2te/ktMRk12huZ5vgg3Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=CNySx9tD; arc=none smtp.client-ip=91.218.175.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="CNySx9tD" Message-ID: <997d3b8a-4b3a-4720-8fa0-2f91447021bd@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1755064799; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Cv0mZfaoxWs8BQP4Uzbmx4o3hMgWue9gP2n4lIHpA6I=; b=CNySx9tD85R6hQwr6H0Ng+Fpr1aZ2L2e4bvv8GG34T1XeUrFHLW1dPqe1qEj6zjuMaokP8 DrmXZuQWcTWT2X9uL+R3VC4BBVhxjU1/adh9jZdkD3m1KmBi7PScOXiKpiU4Xsaa7CnQWt 54XK/S5/JG2eo3sWb4DI2xjGD0H2GFM= Date: Tue, 12 Aug 2025 22:59:52 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v3 2/2] bpf: fix stackmap overflow check in __bpf_get_stackid() Content-Language: en-GB To: Arnaud Lecomte 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 References: <20250812193034.18848-1-contact@arnaud-lcm.com> <20250812193256.19029-1-contact@arnaud-lcm.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yonghong Song In-Reply-To: <20250812193256.19029-1-contact@arnaud-lcm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 8/12/25 12:32 PM, 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 > > Reported-by: syzbot+c9b724fbb41cf2538b7b@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=c9b724fbb41cf2538b7b > Signed-off-by: Arnaud Lecomte LGTM with a few nits below. Acked-by: Yonghong Song > --- > kernel/bpf/stackmap.c | 24 ++++++++++++++---------- > 1 file changed, 14 insertions(+), 10 deletions(-) > > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > index a267567e36dd..e1ee18cbbbb2 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)) > @@ -392,16 +393,18 @@ 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; > } else { /* user */ > + Remove the above empty line. > u64 skip = flags & BPF_F_SKIP_FIELD_MASK; > > skip += nr_kernel; > @@ -409,7 +412,8 @@ 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; > }