[PATCH v13 7/9] ima: verify if the segment size has changed

[steven chen <chenste@linux.microsoft.com>]

From: Steven Chen <chenste@linux.microsoft.com>

kexec 'load' may be called multiple times. Free and realloc the buffer
only if the segment_size is changed from the previous kexec 'load' call.

Signed-off-by: Steven Chen <chenste@linux.microsoft.com>
Acked-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
 security/integrity/ima/ima_kexec.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
index 5c3b3e0b2186..ed867734ee70 100644
--- a/security/integrity/ima/ima_kexec.c
+++ b/security/integrity/ima/ima_kexec.c
@@ -33,6 +33,14 @@ static void ima_free_kexec_file_buf(struct seq_file *sf)
 
 static int ima_alloc_kexec_file_buf(size_t segment_size)
 {
+	/*
+	 * kexec 'load' may be called multiple times.
+	 * Free and realloc the buffer only if the segment_size is
+	 * changed from the previous kexec 'load' call.
+	 */
+	if (ima_kexec_file.buf && ima_kexec_file.size == segment_size)
+		goto out;
+
 	ima_free_kexec_file_buf(&ima_kexec_file);
 
 	/* segment size can't change between kexec load and execute */
@@ -41,6 +49,8 @@ static int ima_alloc_kexec_file_buf(size_t segment_size)
 		return -ENOMEM;
 
 	ima_kexec_file.size = segment_size;
+
+out:
 	ima_kexec_file.read_pos = 0;
 	ima_kexec_file.count = sizeof(struct ima_kexec_hdr);	/* reserved space */
 
-- 
2.43.0