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

Lakshmi Ramasubramanian
2021-01-21T17:32:19Z

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 <nramas@linux.microsoft.com>
Suggested-by: Tyler Hicks <tyhicks@linux.microsoft.com>
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 212145008a01..8eadd0674629 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/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);
}
--
2.30.0