linux-kernel - [PATCH v3] md/raid1: Fix stack memory use after return in raid1

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Message-ID: <20250612112901.3023950-1-wangjinchao600@gmail.com>
Date: Thu, 12 Jun 2025 19:28:40 +0800
From: Wang Jinchao <wangjinchao600@...il.com>
To: Song Liu <song@...nel.org>,
	Yu Kuai <yukuai3@...wei.com>
Cc: Wang Jinchao <wangjinchao600@...il.com>,
	linux-raid@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3] md/raid1: Fix stack memory use after return in raid1_reshape

In the raid1_reshape function, newpool is
allocated on the stack and assigned to conf->r1bio_pool.
This results in conf->r1bio_pool.wait.head pointing
to a stack address.
Accessing this address later can lead to a kernel panic.

Example access path:

raid1_reshape()
{
	// newpool is on the stack
	mempool_t newpool, oldpool;
	// initialize newpool.wait.head to stack address
	mempool_init(&newpool, ...);
	conf->r1bio_pool = newpool;
}

raid1_read_request() or raid1_write_request()
{
	alloc_r1bio()
	{
		mempool_alloc()
		{
			// if pool->alloc fails
			remove_element()
			{
				--pool->curr_nr;
			}
		}
	}
}

mempool_free()
{
	if (pool->curr_nr < pool->min_nr) {
		// pool->wait.head is a stack address
		// wake_up() will try to access this invalid address
		// which leads to a kernel panic
		return;
		wake_up(&pool->wait);
	}
}

Fix:
reinit conf->r1bio_pool.wait after assigning newpool.

Signed-off-by: Wang Jinchao <wangjinchao600@...il.com>
---
 drivers/md/raid1.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 19c5a0ce5a40..fd4ce2a4136f 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -3428,6 +3428,7 @@ static int raid1_reshape(struct mddev *mddev)
 	/* ok, everything is stopped */
 	oldpool = conf->r1bio_pool;
 	conf->r1bio_pool = newpool;
+	init_waitqueue_head(&conf->r1bio_pool.wait);
 
 	for (d = d2 = 0; d < conf->raid_disks; d++) {
 		struct md_rdev *rdev = conf->mirrors[d].rdev;
-- 
2.43.0