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linux-arm-kernel , James Morris , Leo Yan Subject: RE: [PATCH v3 3/4] perf: Use CAP_SYSLOG with kptr_restrict checks Thread-Topic: [PATCH v3 3/4] perf: Use CAP_SYSLOG with kptr_restrict checks Thread-Index: AQHVTS6ohXVeHma7aEyJ5mLyFs0geab7PiSAgAAMNACAAAEdgP//yqiwgAHfTwCAABf5AIAF9+gAgAASvOA= Date: Mon, 19 Aug 2019 22:22:07 +0000 Message-ID: <3f70f6be3a464ca5b4cf563433933245@usma1ex-dag1mb6.msg.corp.akamai.com> References: <291d2cda6ee75b4cd4c9ce717c177db18bf03a31.1565188228.git.ilubashe@akamai.com> <20190814184814.GM9280@kernel.org> <20190814185213.GN9280@kernel.org> <23f7b8c7616a467c93ee2c77e8ffd3cf@usma1ex-dag1mb6.msg.corp.akamai.com> <20190815214236.GA3929@kernel.org> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [172.19.35.136] Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure 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(8.16.0.42/8.16.0.42) with SMTP id x7JMHQw4002057; Mon, 19 Aug 2019 23:22:10 +0100 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=akamai.com; h=from : to : cc : subject : date : message-id : references : in-reply-to : content-type : content-transfer-encoding : mime-version; s=jan2016.eng; bh=969iK0KoMTDmd30EtoPMBUW6pfjiH9io2P6tG8MD6S8=; b=ER8ULjp6504ZePYOpbXzhzjyBELAPaOqhAMiPk5uMTP2PAUr7S3z9ptZc0EmXtyAZ0fr /w+LBsAb0NxA1z1CqNbiQr1TdeDIUSX1/fI5nV+wh00MHTMPuiV2xw1qgFBlUBtBOoly 53r4mCkQQYNDIQwYhvGOTWt0F9GqPl67y0hVEBdOoQb26wxx+M/yE3LWPeTqELVQQfkx 4dl60GDq2BKc6v2anJ+vUDau1C6+dH9aZo8FNiVOzHb/r6fwrDu/Lv/V4E+NpzwuL3Pi D6s2H6fC3qek0Dsd9KtuOkqfI4A34Y1zpg0s40+kvMcoQSRHlTqPAsBw9j9lwRshwilF 3g== Received: from prod-mail-ppoint2 (prod-mail-ppoint2.akamai.com [184.51.33.19] (may be forged)) by m0050096.ppops.net-00190b01. with ESMTP id 2uea0b38ny-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 19 Aug 2019 23:22:09 +0100 Received: from pps.filterd (prod-mail-ppoint2.akamai.com [127.0.0.1]) by prod-mail-ppoint2.akamai.com (8.16.0.27/8.16.0.27) with SMTP id x7JMGjOV007294; Mon, 19 Aug 2019 18:22:08 -0400 Received: from email.msg.corp.akamai.com ([172.27.123.30]) by prod-mail-ppoint2.akamai.com with ESMTP id 2uecwvb3t3-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NOT); Mon, 19 Aug 2019 18:22:08 -0400 Received: from usma1ex-dag1mb6.msg.corp.akamai.com (172.27.123.65) by usma1ex-dag1mb2.msg.corp.akamai.com (172.27.123.102) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Mon, 19 Aug 2019 18:22:07 -0400 Received: from usma1ex-dag1mb6.msg.corp.akamai.com ([172.27.123.65]) by usma1ex-dag1mb6.msg.corp.akamai.com ([172.27.123.65]) with mapi id 15.00.1473.005; Mon, 19 Aug 2019 18:22:07 -0400 From: "Lubashev, Igor" To: Mathieu Poirier , Arnaldo Carvalho de Melo Subject: RE: [PATCH v3 3/4] perf: Use CAP_SYSLOG with kptr_restrict checks Thread-Topic: [PATCH v3 3/4] perf: Use CAP_SYSLOG with kptr_restrict checks Thread-Index: AQHVTS6ohXVeHma7aEyJ5mLyFs0geab7PiSAgAAMNACAAAEdgP//yqiwgAHfTwCAABf5AIAF9+gAgAASvOA= Date: Mon, 19 Aug 2019 22:22:07 +0000 Message-ID: <3f70f6be3a464ca5b4cf563433933245@usma1ex-dag1mb6.msg.corp.akamai.com> References: <291d2cda6ee75b4cd4c9ce717c177db18bf03a31.1565188228.git.ilubashe@akamai.com> <20190814184814.GM9280@kernel.org> <20190814185213.GN9280@kernel.org> <23f7b8c7616a467c93ee2c77e8ffd3cf@usma1ex-dag1mb6.msg.corp.akamai.com> <20190815214236.GA3929@kernel.org> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [172.19.35.136] MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-08-19_04:, , signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908190221 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:5.22.84,1.0.8 definitions=2019-08-19_04:2019-08-19,2019-08-19 signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxscore=0 mlxlogscore=999 clxscore=1015 phishscore=0 bulkscore=0 spamscore=0 adultscore=0 lowpriorityscore=0 suspectscore=0 malwarescore=0 impostorscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1906280000 definitions=main-1908190221 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190819_152227_607823_BA6459D7 X-CRM114-Status: GOOD ( 31.38 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Suzuki K Poulose , Peter Zijlstra , Alexey Budankov , Linux Kernel Mailing List , James Morris , Alexander Shishkin , Ingo Molnar , Leo Yan , Namhyung Kim , Jiri Olsa , linux-arm-kernel Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, August 19, 2019 at 12:51 PM Mathieu Poirier wrote: > On Thu, 15 Aug 2019 at 15:42, Arnaldo Carvalho de Melo > wrote: > > > > Em Thu, Aug 15, 2019 at 02:16:48PM -0600, Mathieu Poirier escreveu: > > > On Wed, 14 Aug 2019 at 14:02, Lubashev, Igor > wrote: > > > > > > > > > On Wed, August 14, 2019 at 2:52 PM Arnaldo Carvalho de Melo > wrote: > > > > > Em Wed, Aug 14, 2019 at 03:48:14PM -0300, Arnaldo Carvalho de > > > > > Melo > > > > > escreveu: > > > > > > Em Wed, Aug 14, 2019 at 12:04:33PM -0600, Mathieu Poirier > escreveu: > > > > > > > # echo 0 > /proc/sys/kernel/kptr_restrict # > > > > > > > ./tools/perf/perf record -e instructions:k uname > > > > > > > perf: Segmentation fault > > > > > > > Obtained 10 stack frames. > > > > > > > ./tools/perf/perf(sighandler_dump_stack+0x44) > > > > > > > [0x55af9e5da5d4] > > > > > > > /lib/x86_64-linux-gnu/libc.so.6(+0x3ef20) [0x7fd31efb6f20] > > > > > > > ./tools/perf/perf(perf_event__synthesize_kernel_mmap+0xa7) > > > > > > > [0x55af9e590337] > > > > > > > ./tools/perf/perf(+0x1cf5be) [0x55af9e50c5be] > > > > > > > ./tools/perf/perf(cmd_record+0x1022) [0x55af9e50dff2] > > > > > > > ./tools/perf/perf(+0x23f98d) [0x55af9e57c98d] > > > > > > > ./tools/perf/perf(+0x23fc9e) [0x55af9e57cc9e] > > > > > > > ./tools/perf/perf(main+0x369) [0x55af9e4f6bc9] > > > > > > > /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe7) > > > > > > > [0x7fd31ef99b97] > > > > > > > ./tools/perf/perf(_start+0x2a) [0x55af9e4f704a] Segmentation > > > > > > > fault > > > > > > > > > > > > > > I can reproduce this on both x86 and ARM64. > > > > > > > > > > > > I don't see this with these two csets removed: > > > > > > > > > > > > 7ff5b5911144 perf symbols: Use CAP_SYSLOG with kptr_restrict > > > > > > checks d7604b66102e perf tools: Use CAP_SYS_ADMIN with > > > > > > perf_event_paranoid checks > > > > > > > > > > > > Which were the ones I guessed were related to the problem you > > > > > > reported, so they are out of my ongoing perf/core pull request > > > > > > to Ingo/Thomas, now trying with these applied and your > instructions... > > > > > > > > > > Can't repro: > > > > > > > > > > [root@quaco ~]# cat /proc/sys/kernel/kptr_restrict > > > > > 0 > > > > > [root@quaco ~]# perf record -e instructions:k uname Linux [ perf > record: > > > > > Woken up 1 times to write data ] [ perf record: Captured and > > > > > wrote 0.024 MB perf.data (1 samples) ] [root@quaco ~]# echo 1 > > > > > > /proc/sys/kernel/kptr_restrict [root@quaco ~]# perf record -e > > > > > instructions:k uname Linux [ perf record: Woken up 1 times to write > data ] [ perf record: > > > > > Captured and wrote 0.024 MB perf.data (1 samples) ] [root@quaco > > > > > ~]# echo > > > > > 0 > /proc/sys/kernel/kptr_restrict [root@quaco ~]# perf record > > > > > -e instructions:k uname Linux [ perf record: Woken up 1 times to > > > > > write data ] [ perf record: Captured and wrote 0.024 MB > > > > > perf.data (1 samples) ] [root@quaco ~]# > > > > > > > > > > [acme@quaco perf]$ git log --oneline --author Lubashev tools/ > > > > > 7ff5b5911144 (HEAD -> perf/cap, acme.korg/tmp.perf/cap, > > > > > acme.korg/perf/cap) perf symbols: Use CAP_SYSLOG with > > > > > kptr_restrict checks d7604b66102e perf tools: Use CAP_SYS_ADMIN > > > > > with perf_event_paranoid checks c766f3df635d perf ftrace: Use > > > > > CAP_SYS_ADMIN instead of euid==0 c22e150e3afa perf tools: Add > > > > > helpers to use capabilities if present > > > > > 74d5f3d06f70 tools build: Add capability-related feature > > > > > detection perf version 5.3.rc4.g7ff5b5911144 [acme@quaco perf]$ > > > > > > > > I got an ARM64 cloud VM, but I cannot reproduce. > > > > # cat /proc/sys/kernel/kptr_restrict > > > > 0 > > > > > > > > Perf trace works fine (does not die): > > > > # ./perf trace -a > > > > > > > > Here is my setup: > > > > Repo: git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git > > > > Branch: tmp.perf/cap > > > > Commit: 7ff5b5911 "perf symbols: Use CAP_SYSLOG with kptr_restrict > checks" > > > > gcc --version: gcc (Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1) 7.4.0 > > > > uname -a: Linux arm-4-par-1 4.9.93-mainline-rev1 #1 SMP Tue Apr 10 > > > > 09:54:46 UTC 2018 aarch64 aarch64 aarch64 GNU/Linux lsb_release > > > > -a: Ubuntu 18.04.3 LTS > > > > > > > > Auto-detecting system features: > > > > ... dwarf: [ on ] > > > > ... dwarf_getlocations: [ on ] > > > > ... glibc: [ on ] > > > > ... gtk2: [ on ] > > > > ... libaudit: [ on ] > > > > ... libbfd: [ on ] > > > > ... libcap: [ on ] > > > > ... libelf: [ on ] > > > > ... libnuma: [ on ] > > > > ... numa_num_possible_cpus: [ on ] > > > > ... libperl: [ on ] > > > > ... libpython: [ on ] > > > > ... libcrypto: [ on ] > > > > ... libunwind: [ on ] > > > > ... libdw-dwarf-unwind: [ on ] > > > > ... zlib: [ on ] > > > > ... lzma: [ on ] > > > > ... get_cpuid: [ OFF ] > > > > ... bpf: [ on ] > > > > ... libaio: [ on ] > > > > ... libzstd: [ on ] > > > > ... disassembler-four-args: [ on ] > > > > > > > > I also could not reproduce on x86: > > > > lsb_release -a: Ubuntu 18.04.1 LTS gcc --version: gcc (Ubuntu > > > > 7.4.0-1ubuntu1~18.04aka10.0.0) 7.4.0 uname -r: 4.4.0-154-generic > > > > > > I isolated the problem to libcap-dev - if it is not installed a > > > segmentation fault will occur. Since this set is about using > > > capabilities it is obvious that not having it on a system should > > > fail a trace session, but it should not crash it. > > > > It shouldn't crash on x86_64: > > > > root@quaco ~]# sysctl kernel.kptr_restrict kernel.kptr_restrict = 0 > > [root@quaco ~]# perf record -e instructions:k uname Linux [ perf > > record: Woken up 1 times to write data ] [ perf record: Captured and > > wrote 0.023 MB perf.data (5 samples) ] [root@quaco ~]# ldd ~/bin/perf > > | grep libcap [root@quaco ~]# perf -v perf version > > 5.3.rc4.g329ca330bf8b [root@quaco ~]# [acme@quaco perf]$ git log > > --oneline -4 329ca330bf8b (HEAD -> perf/cap) perf symbols: Use > > CAP_SYSLOG with kptr_restrict checks f7b9999387af perf tools: Use > > CAP_SYS_ADMIN with perf_event_paranoid checks > > 4d0489cf1c47 (acme.korg/tmp.perf/script-switch-on-off, perf/core) perf > > report: Add --switch-on/--switch-off events > > 2f53ae347f59 perf top: Add --switch-on/--switch-off events [acme@quaco > > perf]$ > > > > > If libcap-dev is not installed function > > > symbol__restricted_filename() will return true, which in turn will > > > prevent symbol_name to be set in > > > machine__get_running_kernel_start(). That prevents function > > > map__set_kallsyms_ref_reloc_sym() from being called in > > > machine__create_kernel_maps(), resulting in kmap->ref_reloc_sym > > > being NULL in _perf_event__synthesize_kernel_mmap() and a > > > segmentation fault. > > > > Can you please try with my perf/cap branch? Perhaps you're using > > Igor's original set of patches? I made changes to the fallback, he was > > making it return false while I made it fallback to geteuid() == 0, as > > was before his patches. > > Things are working properly on your perf/cap branch. I tested with on both > x86 and ARM. Mathieu, you are probably testing with euid==0. If you were to test with euid!=0 but with CAP_SYSLOG and no libcap (and kptr_restrict=0, perf_event_paranoid=2), you would likely hit the bug that you identified in __perf_event__synthesize_kermel_mmap(). See https://lkml.kernel.org/lkml/930a59730c0d495f8c5acf4f99048e8d@usma1ex-dag1mb6.msg.corp.akamai.com for the fix (Option 1 only or Options 1+2). Arnaldo, once we decide what the right fix is, I am happy to post the update (options 1, 1+2) as a patch series. - Igor > > > I am not sure how this can be fixed. I counted a total of 19 > > > instances where kmap->ref_reloc_sym->XYZ is called, only 2 of wich > > > care to check if kmap->ref_reloc_sym is valid before proceeding. As > > > such I must hope that in the 17 other cases, kmap->ref_reloc_sym is > > > guaranteed to be valid. If I am correct then all we need is to > > > check for a valid pointer in _perf_event__synthesize_kernel_mmap(). > > > Otherwise it will be a little harder. > > > > > > Mathieu _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel