Re: [PATCH v2 2/2] ima: Free IMA measurement buffer after kexec syscall

[Greg KH]

On Thu, Feb 04, 2021 at 09:49:51AM -0800, Lakshmi Ramasubramanian wrote:
> 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 
> Suggested-by: Tyler Hicks 
> Reviewed-by: Thiago Jung Bauermann 
> Reviewed-by: Tyler Hicks 
> Fixes: 7b8589cc29e7 ("ima: on soft reboot, save the measurement list")
> ---
>  include/linux/kexec.h  | 5 +
>  kernel/kexec_file.c| 5 +
>  security/integrity/ima/ima_kexec.c | 2 ++
>  3 files changed, 12 insertions(+)



This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

[PATCH v2 2/2] ima: Free IMA measurement buffer after kexec syscall

[Lakshmi Ramasubramanian]

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 
Suggested-by: Tyler Hicks 
Reviewed-by: Thiago Jung Bauermann 
Reviewed-by: Tyler Hicks 
Fixes: 7b8589cc29e7 ("ima: on soft reboot, save the measurement list")
---
 include/linux/kexec.h  | 5 +
 kernel/kexec_file.c| 5 +
 security/integrity/ima/ima_kexec.c | 2 ++
 3 files changed, 12 insertions(+)

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 9e93bef52968..5f61389f5f36 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -300,6 +300,11 @@ struct kimage {
/* Information for loading purgatory */
struct purgatory_info purgatory_info;
 #endif
+
+#ifdef CONFIG_IMA_KEXEC
+   /* Virtual address of IMA measurement buffer for kexec syscall */
+   void *ima_buffer;
+#endif
 };
 
 /* kexec interface functions */
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index b02086d70492..5c3447cf7ad5 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -166,6 +166,11 @@ void kimage_file_post_load_cleanup(struct kimage *image)
vfree(pi->sechdrs);
pi->sechdrs = NULL;
 
+#ifdef CONFIG_IMA_KEXEC
+   vfree(image->ima_buffer);
+   image->ima_buffer = NULL;
+#endif /* CONFIG_IMA_KEXEC */
+
/* See if architecture has anything to cleanup post load */
arch_kimage_file_post_load_cleanup(image);
 
diff --git a/security/integrity/ima/ima_kexec.c 
b/security/integrity/ima/ima_kexec.c
index 206ddcaa5c67..e29bea3dd4cc 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -129,6 +129,8 @@ 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);
 }
-- 
2.30.0