From nobody Sat Feb 7 18:16:03 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 815CF21B9C5; Sun, 28 Dec 2025 18:31:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766946676; cv=none; b=lPgq0dmpKuAeX8ubvj55z88tSsDN2Mwu/rwhdot4Fow27y4H2koS/Zc8SHmrOHiZQn1R7Ciy7DESfw3eGIttgPjVxsooVX/9cr9I3UpA7nI//AXymcW20foyV0DpAijD2MJNQeWesV1uRf8hneO84GHg/YDBoDMYfAUgJ+18EZs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1766946676; c=relaxed/simple; bh=Nl0zExVnGcv+a6pnsdYADQIl//NbnM0mSNK2Npcc274=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=gB396pe7TLfWppJrvbSD6nD5i9uzp7NWyoy8r64gfJVb8MWW53uwSSUuR2ZhjFMtA3Pu34Y+GCdoVAeblmKrNL7tdsZRcCsQPcA6LkmyXj0gfO32j72+DJ1akNbktEo2iVmXPC/sup0HI44f4JnygKzwDe+jqxwvwvYgKn0gT9c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DYnZ8Xo9; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DYnZ8Xo9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2152C4CEFB; Sun, 28 Dec 2025 18:31:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1766946676; bh=Nl0zExVnGcv+a6pnsdYADQIl//NbnM0mSNK2Npcc274=; h=From:To:Cc:Subject:Date:From; 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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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; } =20 +/* + * 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 @c= tx is + * not running (inactive). See if @ctx handled @control or not, and clean= up + * @control if it was not handled. + * + * Returns 0 if @control was handled by @ctx, negative error code otherwis= e. + */ +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 =3D=3D 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_ca= ll_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 --=20 2.47.3