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Fri, 20 Mar 2026 17:36:02 +0100 (CET) From: Josh Law To: SeongJae Park , Andrew Morton Cc: damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Josh Law , stable@vger.kernel.org Subject: [PATCH v2 3/3] mm/damon/sysfs: check contexts->nr in repeat_call_fn Date: Fri, 20 Mar 2026 16:35:59 +0000 Message-Id: <20260320163559.178101-3-objecting@objecting.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260320163559.178101-1-objecting@objecting.org> References: <20260320163559.178101-1-objecting@objecting.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-ZohoMailClient: External X-Stat-Signature: bbuxdpgjbi3833mz7epec3xw8ude9xqg X-Rspam-User: X-Rspamd-Queue-Id: EF3EB1C0019 X-Rspamd-Server: rspam12 X-HE-Tag: 1774024574-208283 X-HE-Meta: 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 u/d65k/Z SOAFuFnXXq1kZDR5RQ/IuJReTVs/OoKHfOd8w4HVnHhbU+xcYOPsLYKCZenVDeV2ILJidcIWE+1k5H6LPqpU48iLUqvOYlnSQ4MS/3RmImAf533R6d+7sjVRsq/jK5j3k3PLAjjJThY4OLsaC1Wk5bEn7PJga/HtJKyWndw+iGGNFFnvuQQrhJRV+XQ33KlVGc0wKpEx7WmI2THzX5HHghTrlm+mBz6R1VxIWv5lhemCW10aM0bhaI+x4RuOKUz/G5trR7doIwxe3P5UpDZCL3VSgwq0FnT2z1fQi30YOtMcuikNMorcIg64PE4UQyEQPIC7NMTJSaJI7+u2pvl7dc4ByxBeFhA0Wm5JGFKppD2tBiYYOO+6qFbeMXPh5q7+U4ZnADsF7HmiwC4A6lADh/FcCr0Vvhte1F0wGVeu5xy2SNbE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: damon_sysfs_repeat_call_fn() calls damon_sysfs_upd_tuned_intervals(), damon_sysfs_upd_schemes_stats(), and damon_sysfs_upd_schemes_effective_quotas() without checking contexts->nr. If nr_contexts is set to 0 via sysfs while DAMON is running, these functions dereference contexts_arr[0] and cause a NULL pointer dereference. Add the missing check. Fixes: d809a7c64ba8 ("mm/damon/sysfs: implement refresh_ms file internal work") Cc: # 6.17.x Signed-off-by: Josh Law Reviewed-by: SeongJae Park --- mm/damon/sysfs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c index ddc30586c0e6..6a44a2f3d8fc 100644 --- a/mm/damon/sysfs.c +++ b/mm/damon/sysfs.c @@ -1620,9 +1620,12 @@ static int damon_sysfs_repeat_call_fn(void *data) if (!mutex_trylock(&damon_sysfs_lock)) return 0; + if (sysfs_kdamond->contexts->nr != 1) + goto out; damon_sysfs_upd_tuned_intervals(sysfs_kdamond); damon_sysfs_upd_schemes_stats(sysfs_kdamond); damon_sysfs_upd_schemes_effective_quotas(sysfs_kdamond); +out: mutex_unlock(&damon_sysfs_lock); return 0; } -- 2.34.1