From: Jason Gunthorpe jgg@nvidia.com
commit 9883c7f84053cec2826ca3c56254601b5ce9cdbe upstream.
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/0-v1-3d5ed1f20d50+104-gup_overflow_jgg@nvidia.com Signed-off-by: Jason Gunthorpe jgg@nvidia.com Reported-by: syzbot+353c7be4964c6253f24a@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/000000000000094fdd05faa4d3a4@google.com Reviewed-by: John Hubbard jhubbard@nvidia.com Reviewed-by: Lorenzo Stoakes lstoakes@gmail.com Reviewed-by: David Hildenbrand david@redhat.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/gup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/gup.c +++ b/mm/gup.c @@ -2977,7 +2977,7 @@ static int internal_get_user_pages_fast( 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)))