ima: Free IMA measurement buffer after kexec syscall

[ Upstream commit f31e3386a4e92ba6eda7328cb508462956c94c64 ]

IMA allocates kernel virtual memory to carry forward the measurement
list, from the current kernel to the next kernel on kexec system call,
in ima_add_kexec_buffer() function.  This buffer is not freed before
completing the kexec system call resulting in memory leak.

Add ima_buffer field in "struct kimage" to store the virtual address
of the buffer allocated for the IMA measurement list.
Free the memory allocated for the IMA measurement list in
kimage_file_post_load_cleanup() function.

Signed-off-by: Lakshmi Ramasubramanian <[email protected]>
Suggested-by: Tyler Hicks <[email protected]>
Reviewed-by: Thiago Jung Bauermann <[email protected]>
Reviewed-by: Tyler Hicks <[email protected]>
Fixes: 7b8589cc29 ("ima: on soft reboot, save the measurement list")
Signed-off-by: Mimi Zohar <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

security/integrity/ima/ima_kexec.c

@@ -130,6 +130,8 @@ void ima_add_kexec_buffer(struct kimage *image)
 		return;
 	}
 
+	image->ima_buffer = kexec_buffer;
+
 	pr_debug("kexec measurement buffer for the loaded kernel at 0x%lx.\n",
 		 kbuf.mem);
 }