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AJvYcCU+gjc7bv8sFxv70ZA/IvByJcGOGXD6tPTlMKK5gAv8bqrjgr46u9kjX3wq49NhNhyyNI92J8f6hw==@kvack.org X-Gm-Message-State: AOJu0Ywcz251x2nok63AYjOCiYNIhSBXQN/z4LbLAGnZBs5dVPjKlbph 4B+C7N9TpyWi+FM7XmzdN0A5e28U1flI5b4iC+nS1RfcOGgLjTXB3E9VOYq+UUnLY71ODq5EEmI c5EhUK7b1foZyw+OpOMITr78DXMQcVWzxL5nD X-Google-Smtp-Source: AGHT+IEPHfQ345gIVazfS+BM1S3fQuD8LMdzMQG/6NL1BywFYIUVmX6NNojvADb+a4swnafGfVK59ZDkwp15Z3Sszpg= X-Received: by 2002:a05:6214:2583:b0:6d3:7a47:2034 with SMTP id 6a1803df08f44-6d4377b32b5mr2495396d6.3.1732044983607; Tue, 19 Nov 2024 11:36:23 -0800 (PST) MIME-Version: 1.0 References: <20241116175922.3265872-1-pasha.tatashin@soleen.com> <2024111938-anointer-kooky-d4f9@gregkh> In-Reply-To: From: Yosry Ahmed Date: Tue, 19 Nov 2024 11:35:47 -0800 Message-ID: Subject: Re: [RFCv1 0/6] Page Detective To: Pasha Tatashin Cc: Roman Gushchin , Greg KH , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, akpm@linux-foundation.org, corbet@lwn.net, derek.kiernan@amd.com, dragan.cvetic@amd.com, arnd@arndb.de, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, tj@kernel.org, hannes@cmpxchg.org, mhocko@kernel.org, shakeel.butt@linux.dev, muchun.song@linux.dev, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, shuah@kernel.org, vegard.nossum@oracle.com, vattunuru@marvell.com, schalla@marvell.com, david@redhat.com, willy@infradead.org, osalvador@suse.de, usama.anjum@collabora.com, andrii@kernel.org, ryan.roberts@arm.com, peterx@redhat.com, oleg@redhat.com, tandersen@netflix.com, rientjes@google.com, gthelen@google.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 2C17AA0012 X-Stat-Signature: 5ctszk3sfkuarhibuwbhrny4uso7p667 X-Rspam-User: X-HE-Tag: 1732044947-177484 X-HE-Meta: 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 J/J5lf+O cO5gLfsXiOt4KbiiCRnUNdzz2Yp3oPbCfEq7y07ENzDN4iVB1wdsr19393JpA18p+95WHLUXvkg0BzqEY+r2+tY5Nko6GFl9zBgMXCyQjpUarjoUkYjLwdhgS0jDQt8sfdiuXpNFS+DN70J5DxX6eZ25KubcbEM5JWTSWDnTR9PF35Z81PMhMEBwMuF2o04RDqnHzwSWVoleimzhsbbc/njKcovkQ2THIJUmqsa5tJsApDjkaeTtUR4FRwCCL19w7ane7UeXM47O9U5AgEYGuhCttGpu28a73NZBnis0ZLS1ZMOLC3lF0VTDYS1AnZdIZ1Rxe X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Nov 19, 2024 at 11:30=E2=80=AFAM Pasha Tatashin wrote: > > On Tue, Nov 19, 2024 at 1:23=E2=80=AFPM Roman Gushchin wrote: > > > > On Tue, Nov 19, 2024 at 10:08:36AM -0500, Pasha Tatashin wrote: > > > On Mon, Nov 18, 2024 at 8:09=E2=80=AFPM Greg KH wrote: > > > > > > > > On Mon, Nov 18, 2024 at 05:08:42PM -0500, Pasha Tatashin wrote: > > > > > Additionally, using crash/drgn is not feasible for us at this tim= e, it > > > > > requires keeping external tools on our hosts, also it requires > > > > > approval and a security review for each script before deployment = in > > > > > our fleet. > > > > > > > > So it's ok to add a totally insecure kernel feature to your fleet > > > > instead? You might want to reconsider that policy decision :) > > > > > > Hi Greg, > > > > > > While some risk is inherent, we believe the potential for abuse here > > > is limited, especially given the existing CAP_SYS_ADMIN requirement. > > > But, even with root access compromised, this tool presents a smaller > > > attack surface than alternatives like crash/drgn. It exposes less > > > sensitive information, unlike crash/drgn, which could potentially > > > allow reading all of kernel memory. > > > > The problem here is with using dmesg for output. No security-sensitive > > information should go there. Even exposing raw kernel pointers is not > > considered safe. > > I am OK in writing the output to a debugfs file in the next version, > the only concern I have is that implies that dump_page() would need to > be basically duplicated, as it now outputs everything via printk's. Perhaps you can refactor the code in dump_page() to use a seq_buf, then have dump_page() printk that seq_buf using seq_buf_do_printk(), and have page detective output that seq_buf to the debugfs file? We do something very similar with memory_stat_format(). We use the same function to generate the memcg stats in a seq_buf, then we use that seq_buf to output the stats to memory.stat as well as the OOM log.