On 20.03.23 03:47, Wupeng Ma wrote:
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.
Add new check and return -EINVAL to fix this overflowing scenarios since
they are absolutely wrong.
Thinking again, wouldn't we reject mlock(0, ULONG_MAX) now as well?
Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx>
---
mm/mlock.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/mm/mlock.c b/mm/mlock.c
index 617469fce96d..eb68476da497 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -568,6 +568,7 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla
unsigned long locked;
unsigned long lock_limit;
int error = -ENOMEM;
+ size_t old_len = len;
start = untagged_addr(start);
@@ -577,6 +578,9 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla
len = PAGE_ALIGN(len + (offset_in_page(start)));
start &= PAGE_MASK;
+ if (old_len != 0 && len == 0)
if (old_len && !len)
+ return -EINVAL;
+
lock_limit = rlimit(RLIMIT_MEMLOCK);
lock_limit >>= PAGE_SHIFT;
locked = len >> PAGE_SHIFT;
@@ -631,12 +635,16 @@ SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
{
int ret;
+ size_t old_len = len;
start = untagged_addr(start);
len = PAGE_ALIGN(len + (offset_in_page(start)));
start &= PAGE_MASK;
+ if (old_len != 0 && len == 0)
if (old_len && !len)
+ return -EINVAL;
+
if (mmap_write_lock_killable(current->mm))
return -EINTR;
ret = apply_vma_lock_flags(start, len, 0);
--
Thanks,
David / dhildenb
