This fixes a bug in commit 63c69ad3d18a ("fuse: refactor
fuse_fill_write_pages()") where max_pages << PAGE_SHIFT is mistakenly
used as the calculation for the max_pages upper limit but there's the
possibility that copy_folio_from_iter_atomic() may copy over bytes
from the iov_iter that are less than the full length of the folio,
which would lead to exceeding max_pages.
This commit fixes it by adding a 'ap->num_folios < max_folios' check.
Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
Fixes: 63c69ad3d18a ("fuse: refactor fuse_fill_write_pages()")
Reported-by: Brian Foster <bfoster@xxxxxxxxxx>
Closes: https://lore.kernel.org/linux-fsdevel/aEq4haEQScwHIWK6@bfoster/
---
fs/fuse/file.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 3d0b33be3824..a05a589dc701 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1147,7 +1147,7 @@ static ssize_t fuse_send_write_pages(struct fuse_io_args *ia,
static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
struct address_space *mapping,
struct iov_iter *ii, loff_t pos,
- unsigned int max_pages)
+ unsigned int max_folios)
{
struct fuse_args_pages *ap = &ia->ap;
struct fuse_conn *fc = get_fuse_conn(mapping->host);
@@ -1157,12 +1157,11 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
int err = 0;
num = min(iov_iter_count(ii), fc->max_write);
- num = min(num, max_pages << PAGE_SHIFT);
ap->args.in_pages = true;
ap->descs[0].offset = offset;
- while (num) {
+ while (num && ap->num_folios < max_folios) {
size_t tmp;
struct folio *folio;
pgoff_t index = pos >> PAGE_SHIFT;
--
2.47.1
