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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 07:10:40 -0700 Message-ID: <20261029141040.148392-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261029075609.35661-1-xiaoleiwangxiaolei@gmail.com> References: X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 05D9F20005 X-Stat-Signature: oyw3xfbusgfx9j1fab156ii6h6xp1oh1 X-Rspam-User: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793283049-872202 X-HE-Meta: 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 5+mWlc1d B9R1UQE7bGzTYwtd6akhu8qchF7FWtdDvh118U+OfP1bDMmQZ9qziNB6cXTauJCRAwLg4S60YDPQxLFdbcmaI9m6UkvMZbHg7jnccrIBW3nLYv30HeLOPZ/Y/LMuUyrzpnNItaKZ3R4i3XOEyFbg1Edx0WrR7LJm1+13Y+t6LegsTxxUTpHDQQSsOqC1w4qzfPvl3P89izoT6IxvvhTySM4ICNmOvmMjYENX/j/D5GNpUgonczG2b6PGY2mAgFmv5mPL8q8d9TtCIfMrV5cxKR/rB8f6yL/EixnPNaZ5wggvqpSq1ujF5a1ZVD5V1H4Zfb1ieUVUZ//7Zelf8D5vdp4EZ+nlV9QFw/dBUqqd5hSjcB9TXFvs+hhXId7nEsM4AHwXDCOyMg6rAfwc9IRaPfUzkmRn0TPQ4lC5rehLeM9ojKTD0ZMbDLmrECDmEF3Yu1AbtAjkFIxpX09OZVtL7SAZeUw== 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 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@. Cc: # 6.7.x > Cc: Liam R. Howlett > Cc: Michal Hocko > Cc: Mike Rapoport > Cc: Suren Baghdasaryan > Cc: Vlastimil Babka > Signed-off-by: Wang Xiaolei Other than Cc: stable@, Reviewed-by: SJ Park Assuming you agree to Cc stable@, I applied this patch to damon/next [1] tree after adding the Cc. I will repost it next Monday, as an mm.git merge request. So, no action from your side is needed for now. [1] https://origin.kernel.org/doc/html/latest/mm/damon/maintainer-profile.html#scm-trees Thanks, SJ [...]