Null-pointer Dereference Vulnerability in Linux Kernel Affecting md/raid5

CVE-2025-71135

What is CVE-2025-71135?

A potential null-pointer dereference vulnerability exists in the Linux kernel's md/raid5 subsystem. The issue arises from an improper handling of the mddev->private variable in the raid5_store_group_thread_cnt() function. If the variable is NULL, subsequent calls to raid5_quiesce() can lead to dereferencing a NULL pointer, causing undefined behavior or system crashes. The vulnerability has been mitigated by implementing a check that ensures mddev is unlocked and properly returns before calling raid5_quiesce() when the private configuration pointer is not valid, thus following the standard practice in similar functions like raid5_change_consistency_policy().

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