1 files changed, 165 insertions, 40 deletions

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index aaaca8a..6e03322 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -78,6 +78,9 @@ extern struct list_head audit_filter_list[];
 /* Indicates that audit should log the full pathname. */
 #define AUDIT_NAME_FULL -1
 
+/* no execve audit message should be longer than this (userspace limits) */
+#define MAX_EXECVE_AUDIT_LEN 7500
+
 /* number of audit rules */
 int audit_n_rules;
 
@@ -965,55 +968,187 @@ static int audit_log_pid_context(struct audit_context *context, pid_t pid,
 	return rc;
 }
 
-static void audit_log_execve_info(struct audit_buffer *ab,
-		struct audit_aux_data_execve *axi)
+/*
+ * to_send and len_sent accounting are very loose estimates.  We aren't
+ * really worried about a hard cap to MAX_EXECVE_AUDIT_LEN so much as being
+ * within about 500 bytes (next page boundry)
+ *
+ * why snprintf?  an int is up to 12 digits long.  if we just assumed when
+ * logging that a[%d]= was going to be 16 characters long we would be wasting
+ * space in every audit message.  In one 7500 byte message we can log up to
+ * about 1000 min size arguments.  That comes down to about 50% waste of space
+ * if we didn't do the snprintf to find out how long arg_num_len was.
+ */
+static int audit_log_single_execve_arg(struct audit_context *context,
+					struct audit_buffer **ab,
+					int arg_num,
+					size_t *len_sent,
+					const char __user *p,
+					char *buf)
 {
-	int i;
-	long len, ret;
-	const char __user *p;
-	char *buf;
+	char arg_num_len_buf[12];
+	const char __user *tmp_p = p;
+	/* how many digits are in arg_num? 3 is the length of a=\n */
+	size_t arg_num_len = snprintf(arg_num_len_buf, 12, "%d", arg_num) + 3;
+	size_t len, len_left, to_send;
+	size_t max_execve_audit_len = MAX_EXECVE_AUDIT_LEN;
+	unsigned int i, has_cntl = 0, too_long = 0;
+	int ret;
+
+	/* strnlen_user includes the null we don't want to send */
+	len_left = len = strnlen_user(p, MAX_ARG_STRLEN) - 1;
 
-	if (axi->mm != current->mm)
-		return; /* execve failed, no additional info */
-
-	p = (const char __user *)axi->mm->arg_start;
+	/*
+	 * We just created this mm, if we can't find the strings
+	 * we just copied into it something is _very_ wrong. Similar
+	 * for strings that are too long, we should not have created
+	 * any.
+	 */
+	if (unlikely((len  = -1) || len > MAX_ARG_STRLEN - 1)) {
+		WARN_ON(1);
+		send_sig(SIGKILL, current, 0);
+	}
 
-	for (i = 0; i < axi->argc; i++, p += len) {
-		len = strnlen_user(p, MAX_ARG_STRLEN);
+	/* walk the whole argument looking for non-ascii chars */
+	do {
+		if (len_left > MAX_EXECVE_AUDIT_LEN)
+			to_send = MAX_EXECVE_AUDIT_LEN;
+		else
+			to_send = len_left;
+		ret = copy_from_user(buf, tmp_p, to_send);
 		/*
-		 * We just created this mm, if we can't find the strings
-		 * we just copied into it something is _very_ wrong. Similar
-		 * for strings that are too long, we should not have created
-		 * any.
+		 * There is no reason for this copy to be short. We just
+		 * copied them here, and the mm hasn't been exposed to user-
+		 * space yet.
 		 */
-		if (!len || len > MAX_ARG_STRLEN) {
+		if (ret) {
 			WARN_ON(1);
 			send_sig(SIGKILL, current, 0);
 		}
-
-		buf = kmalloc(len, GFP_KERNEL);
-		if (!buf) {
-			audit_panic("out of memory for argv string\n");
+		buf[to_send] = '\0';
+		has_cntl = audit_string_contains_control(buf, to_send);
+		if (has_cntl) {
+			/*
+			 * hex messages get logged as 2 bytes, so we can only
+			 * send half as much in each message
+			 */
+			max_execve_audit_len = MAX_EXECVE_AUDIT_LEN / 2;
 			break;
 		}
+		len_left -= to_send;
+		tmp_p += to_send;
+	} while (len_left > 0);
+
+	len_left = len;
+
+	if (len > max_execve_audit_len)
+		too_long = 1;
+
+	/* rewalk the argument actually logging the message */
+	for (i = 0; len_left > 0; i++) {
+		int room_left;
+
+		if (len_left > max_execve_audit_len)
+			to_send = max_execve_audit_len;
+		else
+			to_send = len_left;
+
+		/* do we have space left to send this argument in this ab? */
+		room_left = MAX_EXECVE_AUDIT_LEN - arg_num_len - *len_sent;
+		if (has_cntl)
+			room_left -= (to_send * 2);
+		else
+			room_left -= to_send;
+		if (room_left < 0) {
+			*len_sent = 0;
+			audit_log_end(*ab);
+			*ab = audit_log_start(context, GFP_KERNEL, AUDIT_EXECVE);
+			if (!*ab)
+				return 0;
+		}
 
-		ret = copy_from_user(buf, p, len);
 		/*
-		 * There is no reason for this copy to be short. We just
-		 * copied them here, and the mm hasn't been exposed to user-
-		 * space yet.
+		 * first record needs to say how long the original string was
+		 * so we can be sure nothing was lost.
+		 */
+		if ((i == 0) && (too_long))
+			audit_log_format(*ab, "a%d_len=%ld ", arg_num,
+					 has_cntl ? 2*len : len);
+
+		/*
+		 * normally arguments are small enough to fit and we already
+		 * filled buf above when we checked for control characters
+		 * so don't bother with another copy_from_user
 		 */
+		if (len >= max_execve_audit_len)
+			ret = copy_from_user(buf, p, to_send);
+		else
+			ret = 0;
 		if (ret) {
 			WARN_ON(1);
 			send_sig(SIGKILL, current, 0);
 		}
+		buf[to_send] = '\0';
+
+		/* actually log it */
+		audit_log_format(*ab, "a%d", arg_num);
+		if (too_long)
+			audit_log_format(*ab, "[%d]", i);
+		audit_log_format(*ab, "=");
+		if (has_cntl)
+			audit_log_hex(*ab, buf, to_send);
+		else
+			audit_log_format(*ab, "\"%s\"", buf);
+		audit_log_format(*ab, "\n");
+
+		p += to_send;
+		len_left -= to_send;
+		*len_sent += arg_num_len;
+		if (has_cntl)
+			*len_sent += to_send * 2;
+		else
+			*len_sent += to_send;
+	}
+	/* include the null we didn't log */
+	return len + 1;
+}
+
+static void audit_log_execve_info(struct audit_context *context,
+				  struct audit_buffer **ab,
+				  struct audit_aux_data_execve *axi)
+{
+	int i;
+	size_t len, len_sent = 0;
+	const char __user *p;
+	char *buf;
 
-		audit_log_format(ab, "a%d=", i);
-		audit_log_untrustedstring(ab, buf);
-		audit_log_format(ab, "\n");
+	if (axi->mm != current->mm)
+		return; /* execve failed, no additional info */
+
+	p = (const char __user *)axi->mm->arg_start;
 
-		kfree(buf);
+	audit_log_format(*ab, "argc=%d ", axi->argc);
+
+	/*
+	 * we need some kernel buffer to hold the userspace args.  Just
+	 * allocate one big one rather than allocating one of the right size
+	 * for every single argument inside audit_log_single_execve_arg()
+	 * should be <8k allocation so should be pretty safe.
+	 */
+	buf = kmalloc(MAX_EXECVE_AUDIT_LEN + 1, GFP_KERNEL);
+	if (!buf) {
+		audit_panic("out of memory for argv string\n");
+		return;
 	}
+
+	for (i = 0; i < axi->argc; i++) {
+		len = audit_log_single_execve_arg(context, ab, i,
+						  &len_sent, p, buf);
+		if (len <= 0)
+			break;
+		p += len;
+	}
+	kfree(buf);
 }
 
 static void audit_log_exit(struct audit_context *context, struct task_struct *tsk)
@@ -1157,7 +1292,7 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
 
 		case AUDIT_EXECVE: {
 			struct audit_aux_data_execve *axi = (void *)aux;
-			audit_log_execve_info(ab, axi);
+			audit_log_execve_info(context, &ab, axi);
 			break; }
 
 		case AUDIT_SOCKETCALL: {
@@ -2094,8 +2229,6 @@ int __audit_ipc_set_perm(unsigned long qbytes, uid_t uid, gid_t gid, mode_t mode
 	return 0;
 }
 
-int audit_argv_kb = 32;
-
 int audit_bprm(struct linux_binprm *bprm)
 {
 	struct audit_aux_data_execve *ax;
@@ -2104,14 +2237,6 @@ int audit_bprm(struct linux_binprm *bprm)
 	if (likely(!audit_enabled || !context || context->dummy))
 		return 0;
 
-	/*
-	 * Even though the stack code doesn't limit the arg+env size any more,
-	 * the audit code requires that _all_ arguments be logged in a single
-	 * netlink skb. Hence cap it :-(
-	 */
-	if (bprm->argv_len > (audit_argv_kb << 10))
-		return -E2BIG;
-
 	ax = kmalloc(sizeof(*ax), GFP_KERNEL);
 	if (!ax)
 		return -ENOMEM;