misc: fastrpc: Fix double free of 'buf' in error path

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: misc: fastrpc: Fix double free of 'buf' in error path smatch warning: drivers/misc/fastrpc.c:1926 fastrpc_req_mmap() error: double free of 'buf' In fastrpc_req_mmap() error path, the fastrpc buffer is freed in fastrpc_req_munmap_impl() if unmap is successful. But in the end, there is an unconditional call to fastrpc_buf_free(). So the above case triggers the double free of fastrpc buf.

References

• https://git.kernel.org/stable/c/f77dc8a75859e559f3238a6d906206259227985e
• https://git.kernel.org/stable/c/bfc1704d909dc9911a558b1a5833d3d61a43a1f2
• https://git.kernel.org/stable/c/e8c276d4dc0e19ee48385f74426aebc855b49aaf