From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 4B9A43ACA49; Sat, 17 Oct 2026 16:38:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792255092; cv=none; b=Ec+PvTnQ1Mo3yzUJHPOSjGvhXnhFCcptcN1moTBEoYfcmkMkmvlCuxi3Xzg9XFPWn1HTEmU/xJEi3OKT1jAGjE3dRK5lZ/IhGrkGZvHkqDDHU/DdWcfAEi5BmkZLe4JdStW494oAq/tSFLJ92kdGvYs1lm+vfkjpj/qEnJyYUsc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792255092; c=relaxed/simple; bh=Bjf0eafEN7mFxb+itBr5gGvGDQqWUPrPa/roIr7KiDI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ud/jCq6RPyp5ftubW50GERvwvBQULGjy++clZRFZgjcAjGhf+W6yGzF4fCVYZc/+oED0Hy0451rvQJ63+XYUcDG7iOp53Fb9olIl4E1hGt2RwJkfIpwua7njUgJvxxh1rB8uM1ycfMLHMCLTVA+TYbM+y7VCUJYOo0ZB0oNzGvI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=wfM6m359; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="wfM6m359" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5D5681F000C4; Sat, 17 Oct 2026 16:38:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792255090; bh=H3lcYsMMhn2cwp8Xf903ahulbvuzZvk07OghAMuMNiY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=wfM6m3596IBHkf6PkCGqq3mdBTeRafIKiqj/9kcVmQe+812ODXrndmTUt7wJyGGEm rOm5kDguBqlkPxHSeSlFTSfpdzEfwGort1gH5wQEP3tjwN+lk+u4nQRd32X/9IUAUu 9MYc70J3z9BJYTYuLedLgGQw/K5O5LpeuqmhATWg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Zheng Qixing , Tang Yizhou , Yu Kuai , Tao Cui , Nilay Shroff , Jens Axboe , Sasha Levin Subject: [PATCH 6.12 663/869] blk-cgroup: fix race between policy activation and blkg destruction Date: Sat, 17 Oct 2026 17:58:24 +0200 Message-ID: <20261017160053.994259036@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160036.979869304@linuxfoundation.org> References: <20261017160036.979869304@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zheng Qixing [ Upstream commit 5313d4d41739b0cb63000747c97bb1217ac45f3e ] When switching an IO scheduler on a block device, blkcg_activate_policy() allocates blkg_policy_data (pd) for all blkgs attached to the queue. However, blkcg_activate_policy() may race with concurrent blkcg deletion, leading to use-after-free and memory leak issues. The use-after-free occurs in the following race: T1 (blkcg_activate_policy): - Successfully allocates pd for blkg1 (loop0->queue, blkcgA) - Fails to allocate pd for blkg2 (loop0->queue, blkcgB) - Enters the enomem rollback path to release blkg1 resources T2 (blkcg deletion): - blkcgA is deleted concurrently - blkg1 is freed via blkg_free_workfn() - blkg1->pd is freed T1 (continued): - Rollback path accesses blkg1->pd->online after pd is freed - Triggers use-after-free In addition, blkg_free_workfn() frees pd before removing the blkg from q->blkg_list. This allows blkcg_activate_policy() to allocate a new pd for a blkg that is being destroyed, leaving the newly allocated pd unreachable when the blkg is finally freed. Fix these races by extending blkcg_mutex coverage to serialize blkcg_activate_policy() rollback and blkg destruction, ensuring pd lifecycle is synchronized with blkg list visibility. Fixes: f1c006f1c685 ("blk-cgroup: synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy()") Signed-off-by: Zheng Qixing Reviewed-by: Tang Yizhou Signed-off-by: Yu Kuai Reviewed-by: Tao Cui Reviewed-by: Nilay Shroff Link: https://patch.msgid.link/20260802112525.3933753-3-yukuai@kernel.org Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-cgroup.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index cc882dc2db7f6..06de4024a9a25 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1561,6 +1561,8 @@ int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol) if (queue_is_mq(q)) blk_mq_freeze_queue(q); + + mutex_lock(&q->blkcg_mutex); retry: spin_lock_irq(&q->queue_lock); @@ -1625,6 +1627,7 @@ int blkcg_activate_policy(struct gendisk *disk, const struct blkcg_policy *pol) spin_unlock_irq(&q->queue_lock); out: + mutex_unlock(&q->blkcg_mutex); if (queue_is_mq(q)) blk_mq_unfreeze_queue(q); if (pinned_blkg) -- 2.53.0