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 C36D62FD7AB; Wed, 13 Aug 2025 20:55:17 +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=1755118520; cv=none; b=cqFau2mq/nlY0+qzbhYV7qEpEQGUHGFgUmrK+iX7wq1fm6JCEOHSh63THciXS20U6mWjMjYO7gix9b8oBXeuPfEI5qmMvMWtlaYu1KTb2mIsj1DxoGSJxcsUoTvye1i4Q/VTWty20tZ/xhuxIpQ4jjBIk0paTrKzcgOVnjnNdeM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755118520; c=relaxed/simple; bh=mmKEliEz08ZU6AKwRXZkn5xNu5Oaqg1/xcPdosg31bw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=WhzFvfpZWTYvwZxcELkbyLAycsdIpI+PqjpaquJ9vC0vGOjHlp2njxMNwkyhmxFacFCahfUgjlNMXR96QUN7NsD0KdHr/IBZLv0ClVXX26m1oN7HeDZyDQvJdIQAHOAzIvmBGT0+NXt6mOiRy09hX+NOMYwbCKUkAohDmdoYAJ0= 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 arnaudlcm-X570-UD.. (unknown [IPv6:2a02:8084:255b:aa00:c54d:a88a:ec30:aa38]) by plesk.hostmyservers.fr (Postfix) with ESMTPSA id D2CF5423D2; Wed, 13 Aug 2025 20:55:14 +0000 (UTC) Authentication-Results: Plesk; spf=pass (sender IP is 2a02:8084:255b:aa00:c54d:a88a:ec30:aa38) smtp.mailfrom=contact@arnaud-lcm.com smtp.helo=arnaudlcm-X570-UD.. Received-SPF: pass (Plesk: connection is authenticated) From: Arnaud Lecomte To: yonghong.song@linux.dev Cc: andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org, contact@arnaud-lcm.com, 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 Subject: [PATCH bpf-next v4 2/2] bpf: fix stackmap overflow check in __bpf_get_stackid() Date: Wed, 13 Aug 2025 21:55:06 +0100 Message-ID: <20250813205506.168069-1-contact@arnaud-lcm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250813204606.167019-1-contact@arnaud-lcm.com> References: <20250813204606.167019-1-contact@arnaud-lcm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-PPP-Message-ID: <175511851573.21342.5061621153040207200@Plesk> X-PPP-Vhost: arnaud-lcm.com 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; } -- 2.43.0