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

riscv: Prevent NULL pointer dereference in machine_kexec_prepare()

A NULL pointer dereference issue is noticed in riscv's
machine_kexec_prepare(), where image->segment[i].buf might be NULL and
copied unchecked.

The NULL buf comes from ima_add_kexec_buffer(), where kbuf is added by
kexec_add_buffer(), but kbuf.buffer is NULL, then it is copied without
a check in machine_kexec_prepare():

  kexec_file_load
    -> kimage_file_alloc_init()
       -> kimage_file_prepare_segments()
          -> ima_add_kexec_buffer()
             -> kexec_add_buffer()
    -> machine_kexec_prepare()
       -> memcpy()

Address this by adding a check before the data copy attempt.

https://git.kernel.org/stable/c/606cc45e871e34b80a2f63874f069387a5b44176

https://git.kernel.org/stable/c/6ad6954492697681ebcfc1beb0eb384406cd4b65

https://git.kernel.org/stable/c/81bbcff0c053c4f5c711c31a9b72fc492bd96c3f

https://git.kernel.org/stable/c/b5f92cc4e24a298bf390b0b189a4b888c0900161

https://git.kernel.org/stable/c/c462e15497dc40abe369b3be7a2c91ac5d1be6f9

https://git.kernel.org/stable/c/d5b2752a17efc165793ae38f2c24b5ed9c04ffde

https://git.kernel.org/stable/c/eadd0c2c76aee6a738f17f251434c77db3c606c8

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