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 451D6199F5 for ; Thu, 20 Jul 2023 08:57:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C20A4C433C8; Thu, 20 Jul 2023 08:57:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689843440; bh=CQqZ7QJgc6PvbYM17c0xVDIeGgS08fvdUg+FQ8jo3/Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hc1DMi9NdE1NYlDUOiUVLlCBwnETJRh4Qb+NN8nAgsfz6hdaZBKCNez7Bvo1HHgVL 5ttHv1K/+GBqt3m0jmZuOqMEbbvufHk5U1jY2B2Zyu22F58H4s2HkHZIHjjwjUES8p DduPMvfKKBX5GGYqnaNxPh97W7s6nDefvRTEBUGOh40IjXRBqvk74HS1qG4o47QHLb ML/Gh3FfvxhDQDUVonQ6/Jhtp2huNz0w9x9zgjZJrlj927aRdYJaRFuJg7MZUyS7M6 Cu1pIMdxHmK4Vw8vN0RfiW6Ob+mBNYvoiIi+UgLSUtlUeveH1yYkv+zr4p/RpPlN81 MFBRNkbIixIEQ== 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 1/2] bpf: Disable preemption in bpf_perf_event_output Date: Thu, 20 Jul 2023 10:57:03 +0200 Message-ID: <20230720085704.190592-2-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 The nesting protection in bpf_perf_event_output relies on disabled preemption, which is guaranteed for kprobes and tracepoints. However bpf_perf_event_output can be also called from uprobes context through bpf_prog_run_array_sleepable function which disables 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: kernel tried to execute NX-protected page - exploit attempt? (uid: 0) BUG: unable to handle page fault for address: ffffffff82be3eea ... Call Trace: ? __die+0x1f/0x70 ? page_fault_oops+0x176/0x4d0 ? exc_page_fault+0x132/0x230 ? asm_exc_page_fault+0x22/0x30 ? perf_output_sample+0x12b/0x910 ? perf_event_output+0xd0/0x1d0 ? bpf_perf_event_output+0x162/0x1d0 ? bpf_prog_c6271286d9a4c938_krava1+0x76/0x87 ? __uprobe_perf_func+0x12b/0x540 ? uprobe_dispatcher+0x2c4/0x430 ? uprobe_notify_resume+0x2da/0xce0 ? atomic_notifier_call_chain+0x7b/0x110 ? exit_to_user_mode_prepare+0x13e/0x290 ? irqentry_exit_to_user_mode+0x5/0x30 ? asm_exc_int3+0x35/0x40 Fixing this by disabling preemption in bpf_perf_event_output. Cc: stable@vger.kernel.org Fixes: 8c7dcb84e3b7 ("bpf: implement sleepable uprobes by chaining gps") Signed-off-by: Jiri Olsa --- kernel/trace/bpf_trace.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 5f2dcabad202..14c9a1a548c9 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -661,8 +661,7 @@ static DEFINE_PER_CPU(int, bpf_trace_nest_level); BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map, u64, flags, void *, data, u64, size) { - struct bpf_trace_sample_data *sds = this_cpu_ptr(&bpf_trace_sds); - int nest_level = this_cpu_inc_return(bpf_trace_nest_level); + struct bpf_trace_sample_data *sds; struct perf_raw_record raw = { .frag = { .size = size, @@ -670,7 +669,12 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map, }, }; struct perf_sample_data *sd; - int err; + int nest_level, err; + + preempt_disable(); + + sds = this_cpu_ptr(&bpf_trace_sds); + nest_level = this_cpu_inc_return(bpf_trace_nest_level); if (WARN_ON_ONCE(nest_level > ARRAY_SIZE(sds->sds))) { err = -EBUSY; @@ -691,6 +695,7 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map, out: this_cpu_dec(bpf_trace_nest_level); + preempt_enable(); return err; } -- 2.41.0