From: Wang Jinchao <wangjinchao600@gmail.com>
Date: Thu, 12 Jun 2025 11:28:40 +0000 (+0800)
Subject: md/raid1: Fix stack memory use after return in raid1_reshape
X-Git-Tag: block-6.16-20250710~2^2~3
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=d67ed2ccd2d1dcfda9292c0ea8697a9d0f2f0d98;p=linux-block.git

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.

Fixes: afeee514ce7f ("md: convert to bioset_init()/mempool_init()")
Signed-off-by: Wang Jinchao <wangjinchao600@gmail.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/linux-raid/20250612112901.3023950-1-wangjinchao600@gmail.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---

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;