md/raid10: fix null-ptr-deref of mreplace in raid10_sync_request

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: md/raid10: fix null-ptr-deref of mreplace in raid10_sync_request There are two check of 'mreplace' in raid10_sync_request(). In the first check, 'need_replace' will be set and 'mreplace' will be used later if no-Faulty 'mreplace' exists, In the second check, 'mreplace' will be set to NULL if it is Faulty, but 'need_replace' will not be changed accordingly. null-ptr-deref occurs if Faulty is set between two check. Fix it by merging two checks into one. And replace 'need_replace' with 'mreplace' because their values are always the same.

References

• https://git.kernel.org/stable/c/45fa023b3334a7ae6f6c4eb977295804222dfa28
• https://git.kernel.org/stable/c/2990e2ece18dd4cca71b3109c80517ad94adb065
• https://git.kernel.org/stable/c/f4368a462b1f9a8ecc2fdb09a28c3d4cad302a4f
• https://git.kernel.org/stable/c/222cc459d59857ee28a5366dc225ab42b22f9272
• https://git.kernel.org/stable/c/b5015b97adda6a24dd3e713c63e521ecbeff25c6
• https://git.kernel.org/stable/c/144c7fd008e0072b0b565f1157eec618de54ca8a
• https://git.kernel.org/stable/c/34817a2441747b48e444cb0e05d84e14bc9443da