CVE-2026-90389: Undefined Security Weakness

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

md: scope memalloc_noio to allocation critical sections

Storing a memalloc_noio_save() token in mddev->noio_flags lets one task save the token and another task restore it. With concurrent suspend sysfs writes, task A can enter PF_MEMALLOC_NOIO, return to userspace still in that scope, and later task B can restore A's saved token.

Avoid tying the token lifetime to mddev. Keep mddev_suspend() and mddev_resume() only responsible for array suspension, and enter PF_MEMALLOC_NOIO only in the MD paths that allocate memory after the array has been suspended. Restore the token before resuming the array.

A reproducer repeatedly writes suspend_lo and suspend_hi from concurrent workers and checks each worker's /proc/self/stat flags before and after the sysfs write.