From mboxrd@z Thu Jan 1 00:00:00 1970 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 3743110FD; Sun, 14 Sep 2025 02:57:10 +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=1757818632; cv=none; b=eqxzH07Yt6+eFsI5ecBHWdjzpJTXN7/2LR2ppSrRcAE96okSzkEeA0jGg+bLW7pGIJOyaQNs3Bg7lbZMDPzUly9ZPToPUhccHyz2v1ggepxMUS7192HHL+3bKNrI/UsNzGx9NLa1civ0Yajy/cE3HrxiG2G2xDxoZJ8ln8aZ87A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757818632; c=relaxed/simple; bh=qvMPxfYnDc2wBVd4IkxHgTXdjuTXTSOO3yLGuEfCGic=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=pAUVE4EInZ8a0qby1rRvBhzDzPh9HxOeaVHSjWfNH/Eb3zgdaaIm21bUMUuteQCq6NHETdH92lmVe4in/aOK5mupIlDO0Ybts0Da4Bn0sAe6g6DZgLV0pu92DvfWD0ORfLtsvrg32fRuhFodpt6i8g2hrn79dM7WfBmHmBbRuWo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fszKJFi6; 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="fszKJFi6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 79C6EC4CEF4; Sun, 14 Sep 2025 02:57:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1757818630; bh=qvMPxfYnDc2wBVd4IkxHgTXdjuTXTSOO3yLGuEfCGic=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fszKJFi68LdVDCs39/Xw+ewOdWNNsKTk+Y1XPlk0ifBbMUZIin7XVGAo+JQoNaRkG uL6w3lwXA1S+CR8hLshwrpwz/a10sVSMAirc/Bw3oYZeh57i7uTudxqi19MhK/fNAZ xu7y92Ng3xBWnzA0UWmeVNuk2bAnKLf5tbd4BfOMFRAyLMX75AjHFG6xCf4MVf9Ulu YYNvZL53JJ4XbCi9cvCasbaDqShUC9r0hVZEaVqQ+zsgXnxsMWQ0o+1svcn1Fa/wux Q7ik7pcXjA82onN6tFXQvvvRnjVE8CJwghh7CesFZswTIKtPQKwEkix283nbp+CKrW zLVS2d8GkUbTQ== From: SeongJae Park To: stable@vger.kernel.org Cc: damon@lists.linux.dev, Stanislav Fort , Stanislav Fort , SeongJae Park , Andrew Morton Subject: [PATCH 6.1.y] mm/damon/sysfs: fix use-after-free in state_show() Date: Sat, 13 Sep 2025 19:57:06 -0700 Message-Id: <20250914025706.1846-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <2025091319-muscular-shorts-753a@gregkh> References: <2025091319-muscular-shorts-753a@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Stanislav Fort state_show() reads kdamond->damon_ctx without holding damon_sysfs_lock. This allows a use-after-free race: CPU 0 CPU 1 ----- ----- state_show() damon_sysfs_turn_damon_on() ctx = kdamond->damon_ctx; mutex_lock(&damon_sysfs_lock); damon_destroy_ctx(kdamond->damon_ctx); kdamond->damon_ctx = NULL; mutex_unlock(&damon_sysfs_lock); damon_is_running(ctx); /* ctx is freed */ mutex_lock(&ctx->kdamond_lock); /* UAF */ (The race can also occur with damon_sysfs_kdamonds_rm_dirs() and damon_sysfs_kdamond_release(), which free or replace the context under damon_sysfs_lock.) Fix by taking damon_sysfs_lock before dereferencing the context, mirroring the locking used in pid_show(). The bug has existed since state_show() first accessed kdamond->damon_ctx. Link: https://lkml.kernel.org/r/20250905101046.2288-1-disclosure@aisle.com Fixes: a61ea561c871 ("mm/damon/sysfs: link DAMON for virtual address spaces monitoring") Signed-off-by: Stanislav Fort Reported-by: Stanislav Fort Reviewed-by: SeongJae Park Cc: Signed-off-by: Andrew Morton (cherry picked from commit 3260a3f0828e06f5f13fac69fb1999a6d60d9cff) Signed-off-by: SeongJae Park --- mm/damon/sysfs.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c index 9ea21b6d266b..18f459a3c9ff 100644 --- a/mm/damon/sysfs.c +++ b/mm/damon/sysfs.c @@ -2093,14 +2093,18 @@ static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr, { struct damon_sysfs_kdamond *kdamond = container_of(kobj, struct damon_sysfs_kdamond, kobj); - struct damon_ctx *ctx = kdamond->damon_ctx; - bool running; + struct damon_ctx *ctx; + bool running = false; - if (!ctx) - running = false; - else + if (!mutex_trylock(&damon_sysfs_lock)) + return -EBUSY; + + ctx = kdamond->damon_ctx; + if (ctx) running = damon_sysfs_ctx_running(ctx); + mutex_unlock(&damon_sysfs_lock); + return sysfs_emit(buf, "%s\n", running ? damon_sysfs_cmd_strs[DAMON_SYSFS_CMD_ON] : damon_sysfs_cmd_strs[DAMON_SYSFS_CMD_OFF]); -- 2.39.5