mm/gup: do not return 0 from pin_user_pages_fast() for bad args
These routines are not intended to return zero, the callers cannot do
anything sane with a 0 return. They should return an error which means
future calls to GUP will not succeed, or they should return some non-zero
number of pinned pages which means GUP should be called again.
If start + nr_pages overflows it should return -EOVERFLOW to signal the
arguments are invalid.
Syzkaller keeps tripping on this when fuzzing GUP arguments.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Jason Gunthorpe <[email protected]>
Reported-by: [email protected]
Closes: https://lore.kernel.org/all/[email protected]
Reviewed-by: John Hubbard <[email protected]>
Reviewed-by: Lorenzo Stoakes <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
diff --git a/mm/gup.c b/mm/gup.c
index ce14d4d..a8336b3 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -3080,7 +3080,7 @@ static int internal_get_user_pages_fast(unsigned long start,
start = untagged_addr(start) & PAGE_MASK;
len = nr_pages << PAGE_SHIFT;
if (check_add_overflow(start, len, &end))
- return 0;
+ return -EOVERFLOW;
if (end > TASK_SIZE_MAX)
return -EFAULT;
if (unlikely(!access_ok((void __user *)start, len)))
