Overview
In the Linux kernel, the following vulnerability has been resolved:
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.