[PATCH] audit: don't deref the syscall args when checking the openat2 open_how::flags

[Paul Moore]

As reported by Jeff, dereferencing the openat2 syscall argument in
audit_match_perm() to obtain the open_how::flags can result in an
oops/page-fault.  This patch fixes this by using the open_how struct
that we store in the audit_context with audit_openat2_how().

Cc: stable at vger.kernel.org
Fixes: 1c30e3af8a79 ("audit: add support for the openat2 syscall")
Reported-by: Jeff Mahoney <jeffm at suse.com>
Signed-off-by: Paul Moore <paul at paul-moore.com>
---
 kernel/auditsc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index fce5d43a933f..a83928cbdcb7 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -185,7 +185,7 @@ static int audit_match_perm(struct audit_context *ctx, int mask)
 	case AUDITSC_EXECVE:
 		return mask & AUDIT_PERM_EXEC;
 	case AUDITSC_OPENAT2:
-		return mask & ACC_MODE((u32)((struct open_how *)ctx->argv[2])->flags);
+		return mask & ACC_MODE((u32)ctx->openat2.flags);
 	default:
 		return 0;
 	}