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[2003:d9:971d:3600:c0da:98ce:2525:c9a0]) by smtp.googlemail.com with ESMTPSA id w8-20020a170906384800b0074a82932e3bsm3898693ejc.77.2022.09.04.10.38.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 04 Sep 2022 10:38:31 -0700 (PDT) Message-ID: Date: Sun, 4 Sep 2022 19:38:30 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.0 Subject: Re: Request to cherry-pick 20401d1058f3f841f35a594ac2fc1293710e55b9 to v5.10 and v5.4 To: Greg Kroah-Hartman , Varsha Teratipally Cc: Andrew Morton , Davidlohr Bueso , Rafael Aquini , Alexander Mikhalitsyn , linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20220902135912.816188-1-teratipally@google.com> Content-Language: en-US From: Manfred Spraul In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 9/2/22 16:27, Greg Kroah-Hartman wrote: > On Fri, Sep 02, 2022 at 01:59:11PM +0000, Varsha Teratipally wrote: >> Hi all, >> >> Commit 20401d1058f3f841f35a594ac2fc1293710e55b9("ipc: replace costly >> bailout check in sysvipc_find_ipc()" fixes a high cve and optimizes the >> costly loop by adding a checkpoint, which I think might be a good >> candidate for the stable branches > What do you mean by "high cve"? > > And that feels like it's an artificial benchmark fixup, what real > workload benefits from this change? Standard ipcs end up parsing /proc/sysvipc/*, thus there are real users where the performance of /proc/sysvsem/* matters. But: The performance of the function was bad since 2007, i.e. why is is now urgent? I do not see a bug that must be fixed. Initial patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/ipc/util.c?id=7ca7e564e049d8b350ec9d958ff25eaa24226352 (core issue: The code needs to find the next entry in an idr. And instead of using idr_get_next(), it uses idr_find() in a for(;;id++) loop.) <<< [manfred@localhost Input]$ rpm -qf /usr/bin/ipcs util-linux-core-2.38-1.fc36.x86_64 [manfred@localhost Input]$ strace -e openat /usr/bin/ipcs openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3 openat(AT_FDCWD, "/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3 openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3 openat(AT_FDCWD, "/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3 openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_TIME", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_TIME", O_RDONLY|O_CLOEXEC) = 3 openat(AT_FDCWD, "/usr/lib64/gconv/gconv-modules.cache", O_RDONLY) = 3 openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/util-linux.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/util-linux.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/util-linux.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/util-linux.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/util-linux.mo", O_RDONLY) = -1 ENOENT (No such file or directory) openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/util-linux.mo", O_RDONLY) = -1 ENOENT (No such file or directory) ------ Message Queues -------- key        msqid      owner      perms      used-bytes messages openat(AT_FDCWD, "/proc/sysvipc/msg", O_RDONLY) = 3 ------ Shared Memory Segments -------- key        shmid      owner      perms      bytes      nattch status openat(AT_FDCWD, "/proc/sysvipc/shm", O_RDONLY) = 3 openat(AT_FDCWD, "/etc/nsswitch.conf", O_RDONLY|O_CLOEXEC) = 3 openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 3 0x00000000 18         manfred    600        524288     2 dest openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 3 0x5125004a 19         manfred    600        3208 1 ------ Semaphore Arrays -------- key        semid      owner      perms      nsems openat(AT_FDCWD, "/proc/sysvipc/sem", O_RDONLY) = 3 openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 3 0x51250047 0          manfred    600        1 openat(AT_FDCWD, "/etc/passwd", O_RDONLY|O_CLOEXEC) = 3 0x51250049 2          manfred    600        1 >>>