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b=KIKOrHyBpox31ZVRgjjA3zukl1E6KLrTpfKB3z5CmMQQlGES4cPmTkgBTV+W+abaE Yn3oPDhTvoexdatR0KdXmseFdWlErL5/gHW16OWxy3y+a3NYWcBub0xVFUhcL0R0Dz YeLssf3oBdUFjmvmqMmCgLB+dr2Vn3mHyoJ/H8j+7uQoE9raMZNoQSxeK6xjizFAaG mBK8gQHJaV6/LLpbDvZLqtRdC9qPHFWdDSv7FVdC+BE6l1s6fk2nN5qNTUF7461Gmi CiVhScCKTtnDN28u4GPlXmrORxZ+MzyRjsrJZf9nw6Ew9nKOH3Fd9URF+2F4+IqITO 065ExZ5yeHuvQ== From: SJ Park To: Andrew Morton Cc: SJ Park , "# 6 . 17 . x" , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Zenghui Yu Subject: [PATCH 5/6] samples/damon/wsse: stop and free damon ctx when damon_call() fails Date: Sun, 28 Jun 2026 14:54:44 -0700 Message-ID: <20260628215447.96166-6-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260628215447.96166-1-sj@kernel.org> References: <20260628215447.96166-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: d4wjah6mrwu94wd5dihjckar8qcrtcyq X-Rspamd-Queue-Id: 3A41B4000A X-Rspamd-Server: rspam06 X-HE-Tag: 1782683696-764863 X-HE-Meta: U2FsdGVkX1+YP/sWZPpTni/fpwfRtU26qcXwPHi5GgDAN/M9rBez7n1cRfz41XwpNRATcyGC37XNKJMLQvvex0q7BkBf2E3MUyW9uqT1zncfn59zAAwXwdBES7W+Mbio2UwRNvmcOPR8KNiGY6q29lnkA8YynbwD2dzjt+wFsF7XD4v6JLX1imGO/L1cDNm2hGvb3XFaPtHbVycNwMHrB/UqmDZAsa6y37/xiZu/vf55uymTyVptsw1GibvzycvtI/PROJIYpJoVkr5Cn/JWQ34jw9t3vGDPdy6xEUPM/6Wt0pT4Azkd0GoW0ZB6vwbs5tlOlTGxJZ/Jsr5I9S2QdYd2tr8FwoTWu/FnhyJUyXsP+2pS3roqP/CWq4/Lnnm9I6l1h+3QM/Vyl0L/qOrabgSgFShijAIXmb8nmeaJWD8ZWMqlSFx/El3y6Vx3F7qOWR0KnyDiauMirijlkmgsLw5nEaWceaIoz3O8cStJ/+q5xsn/rXUB5hUc6nUKi8X9N1uh8E+frqqi3AAY+4hSum0QS2CpjblOwgPIixo1eAzCg+Yjdb4iAX6/Gne4qkNSkKNESKzvOIPXDaomaatOTm4C+4mBJ1XkXv8/16x8cFx5ETkdiJYJtYf9c2jSLuZx2BJVylIp5bixsMZzCbK1oDzyFoLoEAUb9O4mYXIyn3MFwl0U5eRAPk9ISgXS2GUJE2AWSjTAO9DQPncR5zbRLjr2Kb4PqMCJVOjrjP3O6NzmWYFxgRFSm92kgmxcG+QAb50YUIqQXnxLTtDjYbcP3b2wf59QhOOcP7LMISazOEH/ESLC8jTzD/YfO9TTJGWQgQUUOc1O3kFhFoB0thzeBVne6WG/BUC6oWbHJTG31JWvd179S6DcbTVJjRuzIF9uXBF7UL987fE5b+GL2zc5z6XSVmysxZAwFXKfd0h8KE6UEQ2O6HwILHyNv0S46kkH8NhE2M0dHpRx4TTwD+Z uvtx8KJh Zlcincl/tg1RHzvMnlkheZr/7AZ0WUfs7gc6BnlIDQLa4x4foDsKAyo+83Umpc3KKm5VSrS4g2JXrw20iJqtOZBaLEgorCIKEO2NqUtHVMNmCSJg2GJOP9VA9iaHSJ/1jQtZNkUSnYRRHPFy+kVRj3iuxuGYt6JW9g5wQ2pTWjJg2r2Lgjcy0yZjPXdrxaTG/5DK3Lm+tJS6096Il8b6CtWgLEwUI9+CWxwxwJbcxm8iN5L0RFqxEaQZK2fpzNIO7/tMzJTXZ0J1eXZYQr/79zZt3KC103FXLKsNB Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: damon_sample_wsse_start() calls damon_call() right after damon_start() is succeeded. The kdamond that has started by the damon_start() could be terminated by itself before or in the middle of the damon_call() execution. There could be multiple reasons for such a stop including monitoring target process termination and kdamond_fn() internal memory allocation failures. In the case, damon_call() will fail and return an error without cleaning up the DAMON context object. The damon_sample_wsse_start() caller assumes it would clean up the object, though. When the user requests to start DAMON again, damon_sample_wsse_start() is called again, allocates a new DAMON context object and overwrites the pointer for the previous object. As a result, the previous context object is leaked. Safely stop the kdamond and deallocate the context object when the failure is returned. Note that the kdamond should be stopped first, because damon_call() failure means not complete termination of the kdamond but only the fact that the termination process has started. The user impact shouldn't be that significant because the race is not easy to happen, and only up to one DAMON context object can be leaked per race. The issue was discovered [1] by Sashiko. [1] https://lore.kernel.org/20260610034828.4632-1-sj@kernel.org Fixes: cc9c1b8c205b ("samples/damon/wsse: use damon_call() repeat mode instead of damon_callback") Cc: # 6.17.x Reviewed-by: Zenghui Yu Signed-off-by: SJ Park --- samples/damon/wsse.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/samples/damon/wsse.c b/samples/damon/wsse.c index bbd9392ab5b36..ff5e8a890f448 100644 --- a/samples/damon/wsse.c +++ b/samples/damon/wsse.c @@ -92,7 +92,12 @@ static int damon_sample_wsse_start(void) return err; } repeat_call_control.data = ctx; - return damon_call(ctx, &repeat_call_control); + err = damon_call(ctx, &repeat_call_control); + if (err) { + damon_stop(&ctx, 1); + damon_destroy_ctx(ctx); + } + return err; } static void damon_sample_wsse_stop(void) -- 2.47.3