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b=EIh1pLpT2Kntma9pyfpR4fjjgcl52ZD0EWa3Cz25JtupEDkZxy8Aja17UnCvyT+Pz ny3Cri1QeNZb6hlymfZYRIqiZIJdBVDzg/HvDq8PDNAt2+sgTI74s+1QP/ceDS3JA1 ALdMpay/0c9/+Xkxxz0HygOZmYjmqJ9I27MNUCoS8SvF9eEl0u9b7p8bbZAun8IRp4 Q1U2bU+dXx8XyTvhbMckUINDlXcw9y50gaypzzgUS5UYxUVuIYYH3GczZRs/znh1g2 o7b/0dEs7SQWm6bcGkFIpmiWX3cAktuRBSuH5JDtDIAcanQxoIDIR4kwXaLKQVZrJo Vr1fnszUF1n/A== From: SeongJae Park To: Cc: SeongJae Park , "# 6 . 17 . x" , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v4 5/6] samples/damon/wsse: stop and free damon ctx when damon_call() fails Date: Wed, 10 Jun 2026 06:55:43 -0700 Message-ID: <20260610135546.64943-6-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260610135546.64943-1-sj@kernel.org> References: <20260610135546.64943-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 6420020004 X-Stat-Signature: xxayh3i58h9xrpckm4ez5zac6d15a76z X-Rspam-User: X-HE-Tag: 1781099759-171030 X-HE-Meta: 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 PMmns/pT cIyLlgnjtr95IINZlkOIAKmgwB1cwVOevtvbi3ndsG46xI+RkK/3KmMcGhACcQT1E6IHG8u+QbPjyqqpGH9QEv1hiWRtAVeBPrvD+4oiubiHFVjFstVGZt51uy+WctsrWswvMSVHjK4XdGG6NKs7ihxSRNmN501UDcM7KriVp5dn9hMVFma2V7XpbU/Q2nYcACGbGEQUeHearYk0pOTUsJqoF9C8LvhYsccHn+Fiq4SEaxaR0GxOPc8G3C5CQ8lh3x8fgO7bhyxV5ErPfWEal5y27OQ== 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 Signed-off-by: SeongJae 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