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b=DYnZ8Xo98Bp2Z6dXet8yKsrCR2Erlm2v2pr7WNLZeGlYXUjXF1TqK/dv4vH7nBE9q 4kudQE8gdhcLigBS2AjF4K2/Q2yCRbphFe4wW1UuBjpeSy5p4DyetWylA/DLGmBoCg lWkdtl0FARxcNKg75U0fO1Ssz+CB8vpSvQUYJ8wRWYPLPNe0VILMCPB/rflOgXTmon xePXxLN72myp/SxUo4UjOwfmVZyHwGuuwO5vQAIFRAKv2h2mPNwOKq1Ql8Qok1y9P2 ewl5MrwUrN7uAZpaVecbOzRi2fly51VlXgher4q4/2KyqwUT8146c/uGn/TITFFw7I MWvuMwVfsqanw== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , "# 6 . 14 . x" , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, JaeJoon Jung Subject: [PATCH] mm/damon/core: remove call_control in inactive contexts Date: Sun, 28 Dec 2025 10:31:01 -0800 Message-ID: <20251228183105.289441-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: nxbhdso1oba6gckwsaz8ca586azfndkm X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 53F6B1C0006 X-HE-Tag: 1766946677-175599 X-HE-Meta: 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 tzv2ZEr6 HmuOOSOC/+Fc4TTN4Y9wMGN1kUE3KYTsti306ny3w2VE6IHUUvRx+w2+4a2SGyE0DEfMP9MI4zQ8GagzccZZ9WPbpxvkU/2iKhTY8F9Xr1FJw8BwpvYzhJ0pIn6XG+jW9MyJLTkdE14sreJQyVkVtRlOpi8cJHC49u0rLlCPcmgbM7tY7eLm1H4MhvrTYt3S6NdxUZiXWSZYXeQofzUWLxqE3ea4hj5qNIysGTScCZt2WewWSvMpGCkRd6e9Frc4k89Mie2RwcLpBU6EvXnmPlly7cRo5xK6WODBvBc7/qJUwIjI= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: If damon_call() is executed against a DAMON context that is not running, the function returns error while keeping the damon_call_control object linked to the context's call_controls list. Let's suppose the object is deallocated after the damon_call(), and yet another damon_call() is executed against the same context. The function tries to add the new damon_call_control object to the call_controls list, which still has the pointer to the previous damon_call_control object, which is deallocated. As a result, use-after-free happens. This can actually be triggered using the DAMON sysfs interface. It is not easily exploitable since it requires the sysfs write permission and making a definitely weird file writes, though. Please refer to the report for more details about the issue reproduction steps. Fix the issue by making damon_call() to cleanup the damon_call_control object before returning the error. Reported-by: JaeJoon Jung Closes: https://lore.kernel.org/20251224094401.20384-1-rgbi3307@gmail.com Fixes: 42b7491af14c ("mm/damon/core: introduce damon_call()") Cc: # 6.14.x Signed-off-by: SeongJae Park --- mm/damon/core.c | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index 2d3e8006db50..65482a0ce20b 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -1442,6 +1442,35 @@ bool damon_is_running(struct damon_ctx *ctx) return running; } +/* + * damon_call_handle_inactive_ctx() - handle DAMON call request that added to + * an inactive context. + * @ctx: The inactive DAMON context. + * @control: Control variable of the call request. + * + * This function is called in a case that @control is added to @ctx but @ctx is + * not running (inactive). See if @ctx handled @control or not, and cleanup + * @control if it was not handled. + * + * Returns 0 if @control was handled by @ctx, negative error code otherwise. + */ +static int damon_call_handle_inactive_ctx( + struct damon_ctx *ctx, struct damon_call_control *control) +{ + struct damon_call_control *c; + + mutex_lock(&ctx->call_controls_lock); + list_for_each_entry(c, &ctx->call_controls, list) { + if (c == control) { + list_del(&control->list); + mutex_unlock(&ctx->call_controls_lock); + return -EINVAL; + } + } + mutex_unlock(&ctx->call_controls_lock); + return 0; +} + /** * damon_call() - Invoke a given function on DAMON worker thread (kdamond). * @ctx: DAMON context to call the function for. @@ -1472,7 +1501,7 @@ int damon_call(struct damon_ctx *ctx, struct damon_call_control *control) list_add_tail(&control->list, &ctx->call_controls); mutex_unlock(&ctx->call_controls_lock); if (!damon_is_running(ctx)) - return -EINVAL; + return damon_call_handle_inactive_ctx(ctx, control); if (control->repeat) return 0; wait_for_completion(&control->completion); base-commit: a100272b3541cb00a5e29fdc16e428234ebfddd1 -- 2.47.3