[PATCH] selinux: check the return value of audit_log_start()

From: xkernel . wang
Date: Fri Jan 14 2022 - 20:13:52 EST


From: Xiaoke Wang <xkernel.wang@xxxxxxxxxxx>

audit_log_start() returns audit_buffer pointer on success or NULL on
error. It is better to check the return value of it so to prevent
potential memory access error.

Signed-off-by: Xiaoke Wang <xkernel.wang@xxxxxxxxxxx>
---
security/selinux/ss/services.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index e5f1b27..759d878 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -3277,11 +3277,13 @@ int security_sid_mls_copy(struct selinux_state *state,
ab = audit_log_start(audit_context(),
GFP_ATOMIC,
AUDIT_SELINUX_ERR);
- audit_log_format(ab,
- "op=security_sid_mls_copy invalid_context=");
- /* don't record NUL with untrusted strings */
- audit_log_n_untrustedstring(ab, s, len - 1);
- audit_log_end(ab);
+ if (ab) {
+ audit_log_format(ab,
+ "op=security_sid_mls_copy invalid_context=");
+ /* don't record NUL with untrusted strings */
+ audit_log_n_untrustedstring(ab, s, len - 1);
+ audit_log_end(ab);
+ }
kfree(s);
}
goto out_unlock;
--