ima: check control characters in policy path

Commit Message

Tianxing Zhang July 7, 2021, 11:45 a.m. UTC

When a policy file path contains control characters like '\r' or '\b',
invalid error messages can be printed to overwrite system messages:

$ echo -e "/\rtest 12345678" > /sys/kernel/security/ima/policy

This patch rejects policy paths with control characters.

Signed-off-by: Tianxing Zhang <[e-mail]>
---
 security/integrity/ima/ima_fs.c | 9 +++++++++
 1 file changed, 9 insertions(+)

Patch

diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 3d8e9d5db5aa..e6daa138de89 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -316,6 +316,7 @@  static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 {
 	char *data;
 	ssize_t result;
+	int i;
 
 	if (datalen >= PAGE_SIZE)
 		datalen = PAGE_SIZE - 1;
@@ -331,6 +332,14 @@  static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 		goto out;
 	}
 
+	for (i = 0; data[i] != '\n' && data[i] != '\0'; i++) {
+		if (iscntrl(data[i])) {
+			pr_err_once("file path with no control characters required\n");
+			result = -EINVAL;
+			goto out_free;
+		}
+	}
+
 	result = mutex_lock_interruptible(&ima_write_mutex);
 	if (result < 0)
 		goto out_free;