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iov: Fix netfs_extract_user_to_sg() 

Fix the loop check in netfs_extract_user_to_sg() for extraction from
user-backed iterators to do the body if npages > 0, not if npages < 0
(which it can never be).

This isn't currently used by cifs, which only ever extracts data from BVEC,
KVEC and XARRAY iterators at this level, user-backed iterators having being
decanted into BVEC iterators at a higher level to accommodate the work
being done in a kernel thread.

Found by smatch:
	fs/netfs/iterator.c:139 netfs_extract_user_to_sg() warn: unsigned 'npages' is never less than zero.

Fixes: 0185846975 ("netfs: Add a function to extract an iterator into a scatterlist")
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202302261115.P3TQi1ZO-lkp@intel.com/
Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/r/Y/yYnAhoAYDBKixX@kili
Reviewed-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: linux-cachefs@redhat.com
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
David Howells 2023-02-27 13:04:54 +00:00 committed by Steve French
parent 0268792f77
commit 4c0421fa6d
1 changed files with 1 additions and 1 deletions
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2
fs/netfs/iterator.c
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@ -134,7 +134,7 @@ static ssize_t netfs_extract_user_to_sg(struct iov_iter *iter,
npages = DIV_ROUND_UP(off + len, PAGE_SIZE);
sg_max -= npages;
for (; npages < 0; npages--) {
for (; npages > 0; npages--) {
struct page *page = *pages;
size_t seg = min_t(size_t, PAGE_SIZE - off, len);