From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 B79C8199F5 for ; Thu, 20 Jul 2023 08:57:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 85816C433C8; Thu, 20 Jul 2023 08:57:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689843451; bh=eWsO3usRBxHzLz/MzFKOIEMz2QGTjBq5921O/fZkWio=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mN8IXOYq6D2qJy2Cf1hagci1WaCtu05O541e5O39kDYn1Qhe0ELeV8YJJSaUf7V92 cgGBEHIoLwi4BXKYiQsgVvzBasJazE7dohFDKEK7P1xU/AUQBw9PCuC6qMK09iITdh MJSB4zGewq9vRi7OIcxOhZjbBYuWYTbZuMevNN1/1HXJPwwG9Yr96o/X68ePuQUOcu CKHaZ44FvM7LJLAOxd/I6b6qNop9ZX0wIPNNZlhdgpYCL7HTXvbyrfbqMWQ89MtMvt v2msdB7rAPQ9EaS5AP4k44FmDeVGIvCgH1P8gHM59EDlFKeKEO3h+QmsmRLkGDD1mN UVXKV6Z+M78wA== From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: stable@vger.kernel.org, bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo Subject: [PATCHv2 bpf 2/2] bpf: Disable preemption in bpf_event_output Date: Thu, 20 Jul 2023 10:57:04 +0200 Message-ID: <20230720085704.190592-3-jolsa@kernel.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230720085704.190592-1-jolsa@kernel.org> References: <20230720085704.190592-1-jolsa@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit We received report [1] of kernel crash, which is caused by using nesting protection without disabled preemption. The bpf_event_output can be called by programs executed by bpf_prog_run_array_cg function that disabled migration but keeps preemption enabled. This can cause task to be preempted by another one inside the nesting protection and lead eventually to two tasks using same perf_sample_data buffer and cause crashes like: BUG: kernel NULL pointer dereference, address: 0000000000000001 #PF: supervisor instruction fetch in kernel mode #PF: error_code(0x0010) - not-present page ... ? perf_output_sample+0x12a/0x9a0 ? finish_task_switch.isra.0+0x81/0x280 ? perf_event_output+0x66/0xa0 ? bpf_event_output+0x13a/0x190 ? bpf_event_output_data+0x22/0x40 ? bpf_prog_dfc84bbde731b257_cil_sock4_connect+0x40a/0xacb ? xa_load+0x87/0xe0 ? __cgroup_bpf_run_filter_sock_addr+0xc1/0x1a0 ? release_sock+0x3e/0x90 ? sk_setsockopt+0x1a1/0x12f0 ? udp_pre_connect+0x36/0x50 ? inet_dgram_connect+0x93/0xa0 ? __sys_connect+0xb4/0xe0 ? udp_setsockopt+0x27/0x40 ? __pfx_udp_push_pending_frames+0x10/0x10 ? __sys_setsockopt+0xdf/0x1a0 ? __x64_sys_connect+0xf/0x20 ? do_syscall_64+0x3a/0x90 ? entry_SYSCALL_64_after_hwframe+0x72/0xdc Fixing this by disabling preemption in bpf_event_output. [1] https://github.com/cilium/cilium/issues/26756 Cc: stable@vger.kernel.org Reported-by: Oleg "livelace" Popov Fixes: 2a916f2f546c bpf: Use migrate_disable/enable in array macros and cgroup/lirc code. Signed-off-by: Jiri Olsa --- kernel/trace/bpf_trace.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 14c9a1a548c9..6826ebf750b0 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -720,7 +720,6 @@ static DEFINE_PER_CPU(struct bpf_trace_sample_data, bpf_misc_sds); u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size, void *ctx, u64 ctx_size, bpf_ctx_copy_t ctx_copy) { - int nest_level = this_cpu_inc_return(bpf_event_output_nest_level); struct perf_raw_frag frag = { .copy = ctx_copy, .size = ctx_size, @@ -737,8 +736,13 @@ u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size, }; struct perf_sample_data *sd; struct pt_regs *regs; + int nest_level; u64 ret; + preempt_disable(); + + nest_level = this_cpu_inc_return(bpf_event_output_nest_level); + if (WARN_ON_ONCE(nest_level > ARRAY_SIZE(bpf_misc_sds.sds))) { ret = -EBUSY; goto out; @@ -753,6 +757,7 @@ u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size, ret = __bpf_perf_event_output(regs, map, flags, sd); out: this_cpu_dec(bpf_event_output_nest_level); + preempt_enable(); return ret; } -- 2.41.0