linux-user: allow NULL arguments to mount
Calls to the mount syscall can legitimately provide NULL as the value
for the source of filesystemtype arguments, which QEMU would previously
reject & return -EFAULT to the target program. An example of this is
remounting an already mounted filesystem with different properties.
Instead of rejecting such syscalls with -EFAULT, pass NULL along to the
kernel as the target program expects.
Additionally this patch fixes a potential memory leak when DEBUG_REMAP
is enabled and lock_user_string fails on the target or filesystemtype
arguments but a prior argument was non-NULL and already locked.
Since the patch already touched most lines of the TARGET_NR_mount case,
it fixes the indentation & coding style for good measure.
Signed-off-by: Paul Burton <paul@archlinuxmips.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 3971cb5..4e48af6 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -5614,29 +5614,60 @@
break;
#endif
case TARGET_NR_mount:
- {
- /* need to look at the data field */
- void *p2, *p3;
- p = lock_user_string(arg1);
- p2 = lock_user_string(arg2);
- p3 = lock_user_string(arg3);
- if (!p || !p2 || !p3)
- ret = -TARGET_EFAULT;
- else {
- /* FIXME - arg5 should be locked, but it isn't clear how to
- * do that since it's not guaranteed to be a NULL-terminated
- * string.
- */
- if ( ! arg5 )
- ret = get_errno(mount(p, p2, p3, (unsigned long)arg4, NULL));
- else
- ret = get_errno(mount(p, p2, p3, (unsigned long)arg4, g2h(arg5)));
- }
+ {
+ /* need to look at the data field */
+ void *p2, *p3;
+
+ if (arg1) {
+ p = lock_user_string(arg1);
+ if (!p) {
+ goto efault;
+ }
+ } else {
+ p = NULL;
+ }
+
+ p2 = lock_user_string(arg2);
+ if (!p2) {
+ if (arg1) {
+ unlock_user(p, arg1, 0);
+ }
+ goto efault;
+ }
+
+ if (arg3) {
+ p3 = lock_user_string(arg3);
+ if (!p3) {
+ if (arg1) {
unlock_user(p, arg1, 0);
- unlock_user(p2, arg2, 0);
- unlock_user(p3, arg3, 0);
- break;
- }
+ }
+ unlock_user(p2, arg2, 0);
+ goto efault;
+ }
+ } else {
+ p3 = NULL;
+ }
+
+ /* FIXME - arg5 should be locked, but it isn't clear how to
+ * do that since it's not guaranteed to be a NULL-terminated
+ * string.
+ */
+ if (!arg5) {
+ ret = mount(p, p2, p3, (unsigned long)arg4, NULL);
+ } else {
+ ret = mount(p, p2, p3, (unsigned long)arg4, g2h(arg5));
+ }
+ ret = get_errno(ret);
+
+ if (arg1) {
+ unlock_user(p, arg1, 0);
+ }
+ unlock_user(p2, arg2, 0);
+ if (arg3) {
+ unlock_user(p3, arg3, 0);
+ }
+ }
+ break;
#ifdef TARGET_NR_umount
case TARGET_NR_umount:
if (!(p = lock_user_string(arg1)))
