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Howlett" , Michal Hocko , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , stable@vger.kernel.org Subject: Re: [PATCH v2] mm/damon/tests/sysfs-kunit: fix leaked pid reference in add_targets test Date: Thu, 29 Oct 2026 17:04:48 -0700 Message-ID: <20261030000449.154316-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: A8553100006 X-Stat-Signature: zfm9p1gsz3h91sxkx3dirrpf97dyqiyd X-Rspamd-Server: rspam01 X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793318697-145468 X-HE-Meta: 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 2cJhGS+C CWx+vhHc6JeZw9LujSPbGV5tKkh6sCzHYc3FEm+7Ux4y5e9ikbwGrXa1FLACL8g6iyI1ntfnoS080yiyJ9qRKhOBgPbY0XNjzy7OhrmgRv8Dtx6h+YXKwG7r61ZDs7ACeTL9T4tSto2b75L2qNEPXAvkf8oPnWdH4w1oRZ5CY3dMNvf/X57iUASJsyVA7COfEHgBdt091loE0bPsKmi34AFATaDaDUKaqvprXbbxdDLefvrYrGAThrXdmo1HFs1bqBbE4WlfdDBcxz3Ohx1EZWcadZUtq3YMocJnwYfk+SsYcztTAY4UpYzcJAA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, 29 Oct 2026 18:18:05 +0300 Dan Carpenter wrote: > On Thu, Oct 29, 2026 at 07:10:40AM -0700, SJ Park wrote: > > Hello Xiaolei, > > > > On Thu, 29 Oct 2026 15:56:09 +0800 Xiaolei Wang wrote: > > > > > From: Wang Xiaolei > > > > > > damon_sysfs_test_add_targets() creates its monitoring context with > > > damon_new_ctx(), which leaves ctx->ops zero-initialized. Since > > > DAMON_OPS_VADDR is zero, damon_target_has_pid() returns true for the > > > context, and damon_sysfs_add_targets() therefore calls > > > damon_set_target_pid() for each target it adds. That function grabs a > > > reference to the target's struct pid via find_get_pid(). > > > > > > The test then tears the context down with damon_destroy_ctx(), which > > > releases such a reference from ctx->ops.cleanup_target(). For the vaddr > > > operations set that callback is damon_va_cleanup_target(), and it is the > > > only place where the reference is put. The test never selects an > > > operations set, though, so cleanup_target is NULL and both references -- > > > one for each of the two damon_sysfs_add_targets() calls -- are leaked on > > > every run of the test. Running the test with CONFIG_DEBUG_KMEMLEAK > > > enabled reports the leaked struct pid objects as unreferenced. > > > > > > Fix this by selecting the vaddr operations set for the context before > > > adding the targets, mirroring what the sysfs interface does. > > > damon_select_ops() fails if the vaddr operations set is not registered, > > > in which case the test cannot exercise the pid handling and skips > > > itself. > > > > Makes sense. Thank you for finding and fixing this. > > > > > > > > Fixes: b8ee5575f763 ("mm/damon/sysfs-test: add a unit test for damon_sysfs_set_targets()") > > > > The impact is leak. I think we should add Cc: stable@. > > I wouldn't bother Cc stable for unit tests. It's not something > which affects production or real life at all. Thank you for your input, Dan! I have no strong opinion. But we got CVEs [1] for this class of unit test code in the past. I'd like to keep it consistent to the past for now. [1] https://lore.kernel.org/2024102930-CVE-2024-50068-2e3c@gregkh/ Thanks, SJ [...]