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bh=Pb0n/eJX1vGIeSAU0z6olfpVOoRIiAMjbL+eNzYDAJ0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WXfrmLYOqHE7GlnSbLzF9j76SGDdJG8FioJpp/hd/WsjiulAP+5c98gzWJ+8390nX IWDlDdIu8HAPtUtEh2CpbkJbyavK2f4/oly7AeMsks7CbQgbPPUWXkPBY8xhR8hLEx 15VrAQ7Y8xZcqeNgHa+ei3/mfAVjIk4LdFrq2kPZU81mH7NDSGub5BUj/oSdvet0m/ 6yU2GE99gvinZ42v1Dth57vOUAgTPip2hnKF/u+uNHlZ4wa8kW9rucJ/ovxVDw+QfU 3iWjnLnmBSkk4cmxT+kz3KvD5ifbtKXTYRxIY4j+UWU/Y+b+hpEGkELVd7gYuMFmkV P85dP2OpJOBmQ== From: SeongJae Park To: Cc: SeongJae Park , "# 6 . 14 . x" , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v4 1/6] samples/damon/wsse: handle damon_start() failure Date: Wed, 10 Jun 2026 06:55:39 -0700 Message-ID: <20260610135546.64943-2-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-Queue-Id: 041E620011 X-Stat-Signature: x4picga61nd4rg46t6uy6nw93d43p56g X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1781099756-712 X-HE-Meta: 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 OEpu2+/S HqHylHepPegDbxbSovSLrCqD+ZGdVRP/3v/izLPCK1om2jekEJu0q9gXdMOF5lATu9tiB3SBykvgCAPnEOb27hH0fJr/+0QneeNOvNoELQtOgXM5EGaUCrCSlAxBlv/LP1Bdnso54sW0UkTv/Bpvzef5SwY1AElYuWKgAAmltMwyJmD95RE7BxIUAd90ALcvTcv5roqktEjh/Jx/lw6Eqc/kRTEXDuOrTuPvo0OlswG488N3DFLp38Wy/tPptqV6miULl4y5j9rNHbrtOI/+JDtjajg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: damon_sample_wsse_start() callers assume it will clean up resources when it fails. And the function does the cleanup for context buildup failures. However, it is not doing the cleanup for damon_start() failure. As a result, when damon_start() fails, it leaks the memory for DAMON context. Free the context in case of the failure to fix the issues. Note that the issue can reliably be reproduced because the module calls damon_start() in the exclusive mode. For example, $ sudo damo start $ echo $$ | sudo tee /sys/module/damon_sample_wsse/parameters/target_pid $ echo Y | sudo tee /sys/module/damon_sample_wsse/parameters/enabled $ sudo cat /proc/allocinfo | grep damon_new_ctx Because the first command is running another DAMON instance, the third command fails the damon_start() call because the new DAMON instance cannot exclusively run. And without this fix, by repeating the third and the fourth commands above, we can show the memory consumption is only increasing due to the leaks. It requires the sudo permission though. The issue was discovered [1] by Sashiko. [1] https://lore.kernel.org/20260609145814.70163-1-sj@kernel.org Fixes: b757c6cfc696 ("samples/damon/wsse: start and stop DAMON as the user requests") Cc: # 6.14.x Signed-off-by: SeongJae Park --- samples/damon/wsse.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/samples/damon/wsse.c b/samples/damon/wsse.c index 799ad44439434..bbd9392ab5b36 100644 --- a/samples/damon/wsse.c +++ b/samples/damon/wsse.c @@ -87,8 +87,10 @@ static int damon_sample_wsse_start(void) target->pid = target_pidp; err = damon_start(&ctx, 1, true); - if (err) + if (err) { + damon_destroy_ctx(ctx); return err; + } repeat_call_control.data = ctx; return damon_call(ctx, &repeat_call_control); } -- 2.47.3