From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta0.migadu.com (out-182.mta0.migadu.com [91.218.175.182]) (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 F36DC8F6E for ; Thu, 7 Aug 2025 19:05:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754593535; cv=none; b=TLrlQuk4hCvLZlDXHrINbsHffuAVAwKJbsygHIHiNtTRdd2Bpx6f89YmQkDLu3q2W+VOpmB9+fX7egN2A3+Q2rMF0WuIoETir46+fV1dKlxzuyl+VqBV2h2sDF+fvvqE04fmGHuPjda+bGEQerWJkyoGXcNx+ub1gvSERMQw6nU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754593535; c=relaxed/simple; bh=dE+AVwYniT3vJHP+UoI8xx4iQ9ExHzmQRWkDYBFHlG4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NkndXbCg3ZKuG/5m9bplkZ+h10w4z0LZsI4SZQm4Uodt/6bUlKEzYGeCH3mp+WAOflmI5COJ2cy0YrYA84cH75GscBxrbFfxLX3e8en1xZgHTQX6163X8I2stqerld64Brafhmw9jj2oqv2+AD92lLYbPtUd7gccFJzZw0B4ZP4= 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=CrxDhWEc; arc=none smtp.client-ip=91.218.175.182 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="CrxDhWEc" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1754593529; 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=G9mKcMRuq6jINq5ANG/Ei6hvRGRifdTxiEw9xKT697k=; b=CrxDhWEcZS33BnpYpxKbyUZQNRwX0NeaXuFlJgj+4DnB3z99uyFAkxDpFvwwjB5JZCQ3ZM YKrVUS+sQqvB7T6+2w1Y3rATiHxbuKWX4h6DQi/QbiffHlff5cQkaKzrRgrrfPthmMMznh 5NJZ+p4V7W8p75Gg74aH9HtBPl92Q6U= Date: Thu, 7 Aug 2025 12:05:23 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH 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: <20250807175032.7381-1-contact@arnaud-lcm.com> <20250807175258.7613-1-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: <20250807175258.7613-1-contact@arnaud-lcm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 8/7/25 10:52 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. > > Reported-by: syzbot+c9b724fbb41cf2538b7b@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=c9b724fbb41cf2538b7b > Signed-off-by: Arnaud Lecomte > --- > kernel/bpf/stackmap.c | 26 +++++++++++++++----------- > 1 file changed, 15 insertions(+), 11 deletions(-) > > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > index 14e034045310..d7ef840971f0 100644 > --- a/kernel/bpf/stackmap.c > +++ b/kernel/bpf/stackmap.c > @@ -250,7 +250,7 @@ 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; > @@ -266,6 +266,8 @@ 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); > @@ -325,19 +327,19 @@ 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); > + if (max_depth < 0) > + return -EFAULT; the above condition is not needed. > > trace = get_perf_callchain(regs, 0, kernel, user, max_depth, > false, false); > @@ -346,7 +348,7 @@ 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 = { > @@ -378,6 +380,7 @@ 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, pe_max_depth; pe_max_depth -> max_depth. > > /* perf_sample_data doesn't have callchain, use bpf_get_stackid */ > if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)) > @@ -396,24 +399,25 @@ 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); > + pe_max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags); > + ret = __bpf_get_stackid(map, trace, flags, pe_max_depth); > > /* restore nr */ > trace->nr = nr; > } else { /* user */ > u64 skip = flags & BPF_F_SKIP_FIELD_MASK; > - please keep an empty line here. > skip += nr_kernel; > if (skip > BPF_F_SKIP_FIELD_MASK) > return -EFAULT; > > flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip; > - ret = __bpf_get_stackid(map, trace, flags); > + pe_max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags); > + ret = __bpf_get_stackid(map, trace, flags, pe_max_depth); > } > return ret; > }