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 1B5E672602; Wed, 17 Sep 2025 12:56:23 +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=1758113783; cv=none; b=GEV2oIIIxuF+QYhzAj2xoP0eIPTt0W6HJ2XJTPERDCuygrpFcMxOXfO6ozxV8DQZgP1+1GV10y+y6NfDrFJ9jiRb/WFOsKWmBYqX2xQ6olgyVor9ZGxoInjvztidSkKgaBdg6U+zX3TQIN3ZAvDZtRbnAUrjTUXiBv11u9WmrpI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758113783; c=relaxed/simple; bh=V9zed4CKwqh2z6e+ChFgISFt7kVh5dWX2kU2+jIGrlw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fxfcVCfKvfbe9aiWdm997iNf2Eyk7x7SMDhfUo+9tlVhdZ4eNfl3cN/PzTWl74wtSo2UX3IAo60y18lNwAK/WryN//z4bLa6wh3EOq6ACjgVMWZsBGYdVeOw3/0Fz8srUQj6i+sZ3PCcU9jMKqoyvmd3bumZDlLy1RDUfpzix/E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=HsuTEQ7K; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="HsuTEQ7K" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8AB64C4CEF0; Wed, 17 Sep 2025 12:56:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1758113783; bh=V9zed4CKwqh2z6e+ChFgISFt7kVh5dWX2kU2+jIGrlw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=HsuTEQ7K9aU15NtIMruVTfrilrVh0A1e922L7FpMJgJzL9hVwQS8WRqmHpS+jYfXb 1XvFhSU2VIHqdNBOaRy+P2Vtt2oP6d/4Xnc840725BQfEY79X9oPhuS4JGD45ppcse V6e/Du/6v1xK55PoUCrotidu5vvcnu1RFBADaBJo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Stanislav Fort , SeongJae Park , Andrew Morton Subject: [PATCH 6.6 050/101] mm/damon/sysfs: fix use-after-free in state_show() Date: Wed, 17 Sep 2025 14:34:33 +0200 Message-ID: <20250917123338.053141678@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250917123336.863698492@linuxfoundation.org> References: <20250917123336.863698492@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stanislav Fort commit 3260a3f0828e06f5f13fac69fb1999a6d60d9cff upstream. 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 Signed-off-by: SeongJae Park Signed-off-by: Greg Kroah-Hartman --- mm/damon/sysfs.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) --- a/mm/damon/sysfs.c +++ b/mm/damon/sysfs.c @@ -1055,14 +1055,18 @@ static ssize_t state_show(struct kobject { 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]);