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[68.134.6.11]) by smtp.gmail.com with ESMTPSA id n6sm19008051qkh.74.2020.08.18.07.31.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Aug 2020 07:31:13 -0700 (PDT) Subject: Re: [PATCH v3 1/3] selinux: add tracepoint on audited events To: =?UTF-8?Q?Thi=c3=a9baud_Weksteen?= , Paul Moore Cc: Nick Kralevich , Joel Fernandes , Peter Enderborg , Eric Paris , Steven Rostedt , Ingo Molnar , Mauro Carvalho Chehab , "David S. Miller" , Rob Herring , linux-kernel@vger.kernel.org, selinux@vger.kernel.org References: <20200817170729.2605279-1-tweek@google.com> <20200817170729.2605279-2-tweek@google.com> From: Stephen Smalley Message-ID: <08b8b541-d558-d290-9593-a8cf18a40c1e@gmail.com> Date: Tue, 18 Aug 2020 10:31:11 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200817170729.2605279-2-tweek@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/17/20 1:07 PM, Thiébaud Weksteen wrote: > The audit data currently captures which process and which target > is responsible for a denial. There is no data on where exactly in the > process that call occurred. Debugging can be made easier by being able to > reconstruct the unified kernel and userland stack traces [1]. Add a > tracepoint on the SELinux denials which can then be used by userland > (i.e. perf). > > Although this patch could manually be added by each OS developer to > trouble shoot a denial, adding it to the kernel streamlines the > developers workflow. > > It is possible to use perf for monitoring the event: > # perf record -e avc:selinux_audited -g -a > ^C > # perf report -g > [...] > 6.40% 6.40% audited=800000 tclass=4 > | > __libc_start_main > | > |--4.60%--__GI___ioctl > | entry_SYSCALL_64 > | do_syscall_64 > | __x64_sys_ioctl > | ksys_ioctl > | binder_ioctl > | binder_set_nice > | can_nice > | capable > | security_capable > | cred_has_capability.isra.0 > | slow_avc_audit > | common_lsm_audit > | avc_audit_post_callback > | avc_audit_post_callback > | > > It is also possible to use the ftrace interface: > # echo 1 > /sys/kernel/debug/tracing/events/avc/selinux_audited/enable > # cat /sys/kernel/debug/tracing/trace > tracer: nop > entries-in-buffer/entries-written: 1/1 #P:8 > [...] > dmesg-3624 [001] 13072.325358: selinux_denied: audited=800000 tclass=4 > > The tclass value can be mapped to a class by searching > security/selinux/flask.h. The audited value is a bit field of the > permissions described in security/selinux/av_permissions.h for the > corresponding class. > > [1] https://source.android.com/devices/tech/debug/native_stack_dump > > Signed-off-by: Thiébaud Weksteen > Suggested-by: Joel Fernandes > Reviewed-by: Peter Enderborg Acked-by: Stephen Smalley