Commit 814a6674 authored by Andreas Gruenbacher's avatar Andreas Gruenbacher
Browse files

iov_iter: Fix iov_iter_get_pages{,_alloc} page fault return value 



Both iov_iter_get_pages and iov_iter_get_pages_alloc return the number
of bytes of the iovec they could get the pages for.  When they cannot
get any pages, they're supposed to return 0, but when the start of the
iovec isn't page aligned, the calculation goes wrong and they return a
negative value.  Fix both functions.

In addition, change iov_iter_get_pages_alloc to return NULL in that case
to prevent resource leaks.

Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
parent 64570fbc

lib/iov_iter.c

+3 −2
Original line number Diff line number Diff line
@@ -1488,7 +1488,7 @@ ssize_t iov_iter_get_pages(struct iov_iter *i, 
		res = get_user_pages_fast(addr, n,

				iov_iter_rw(i) != WRITE ?  FOLL_WRITE : 0,

				pages);

		if (unlikely(res < 0))

		if (unlikely(res <= 0))

			return res;

		return (res == n ? len : res * PAGE_SIZE) - *start;

	}
@@ -1612,8 +1612,9 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, 
			return -ENOMEM;

		res = get_user_pages_fast(addr, n,

				iov_iter_rw(i) != WRITE ?  FOLL_WRITE : 0, p);

		if (unlikely(res < 0)) {

		if (unlikely(res <= 0)) {

			kvfree(p);

			*pages = NULL;

			return res;

		}

		*pages = p;