On 1/22/21 2:30 PM, Thiago Jung Bauermann wrote:

Hi Lakshmi,

Lakshmi Ramasubramanian [off-list ref] writes:

quoted

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.  In error code paths this memory
is not freed resulting in memory leak.

Free the memory allocated for the IMA measurement list in
the error code paths in ima_add_kexec_buffer() function.

Signed-off-by: Lakshmi Ramasubramanian <redacted>
Suggested-by: Tyler Hicks <redacted>
Fixes: 7b8589cc29e7 ("ima: on soft reboot, save the measurement list")
---
  security/integrity/ima/ima_kexec.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 121de3e04af2..212145008a01 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c

@@ -119,12 +119,14 @@ void ima_add_kexec_buffer(struct kimage *image)
  	ret = kexec_add_buffer(&kbuf);
  	if (ret) {
  		pr_err("Error passing over kexec measurement buffer.\n");
+		vfree(kexec_buffer);
  		return;
  	}

This is a good catch.

Thanks.

quoted

  
  	ret = arch_ima_add_kexec_buffer(image, kbuf.mem, kexec_segment_size);
  	if (ret) {
  		pr_err("Error passing over kexec measurement buffer.\n");
+		vfree(kexec_buffer);
  		return;
  	}

But this would cause problems, because the buffer is still there in the
kimage and would cause kimage_load_segment() to access invalid memory.

There's no function to undo a kexec_add_buffer() to avoid this problem,
so I'd suggest just accepting the leak in this case. Fortunately, the
current implementations of arch_ima_add_kexec_buffer() are very simple
and cannot fail, so this is a theoretical problem.

Agreed. I'll post a new patch with the above change removed.

thanks,
  -lakshmi