diff mbox series

[v8,01/17] iov_iter: Fix iov_iter_get_pages{,_alloc} page fault return value

Message ID 20211019134204.3382645-2-agruenba@redhat.com
State New
Headers show
Series gfs2: Fix mmap + page fault deadlocks | expand

Commit Message

Andreas Gruenbacher Oct. 19, 2021, 1:41 p.m. UTC 
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: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 lib/iov_iter.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 755c10c5138c..60b5e6edfbaa 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -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;