[PATCH 1/4] mm/mlock: return EINVAL for illegal user memory range in mlock

[Wupeng Ma]

From: Ma Wupeng <mawupeng1@xxxxxxxxxx>

While testing mlock, we have a problem if the len of mlock is ULONG_MAX.
The return value of mlock is zero. But nothing will be locked since the
len in do_mlock overflows to zero due to the following code in mlock:

  len = PAGE_ALIGN(len + (offset_in_page(start)));

The same problem happens in munlock.

Since TASK_SIZE is the maximum user space address. The start or len of
mlock shouldn't be bigger than this. Function access_ok can be used to
check this issue, so return -EINVAL if bigger.

Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx>
---
 mm/mlock.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/mlock.c b/mm/mlock.c
index 7032f6dd0ce1..b9422a62a4cf 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -575,6 +575,9 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla
 	if (!can_do_mlock())
 		return -EPERM;
 
+	if (unlikely(!access_ok((void __user *)start, len)))
+		return -EINVAL;
+
 	len = PAGE_ALIGN(len + (offset_in_page(start)));
 	start &= PAGE_MASK;
 
@@ -635,6 +638,9 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
 
 	start = untagged_addr(start);
 
+	if (unlikely(!access_ok((void __user *)start, len)))
+		return -EINVAL;
+
 	len = PAGE_ALIGN(len + (offset_in_page(start)));
 	start &= PAGE_MASK;
 
-- 
2.25.1