Unverified Commit dbee298c authored by Joanne Koong's avatar Joanne Koong Committed by Christian Brauner
Browse files

fuse: fix fuse_fill_write_pages() upper bound calculation 



This fixes a bug in commit 63c69ad3 ("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: default avatarJoanne Koong <joannelkoong@gmail.com>
Link: https://lore.kernel.org/20250614000114.910380-1-joannelkoong@gmail.com


Fixes: 63c69ad3 ("fuse: refactor fuse_fill_write_pages()")
Tested-by: default avatarBrian Foster <bfoster@redhat.com>
Reported-by: default avatarBrian Foster <bfoster@redhat.com>
Closes: https://lore.kernel.org/linux-fsdevel/aEq4haEQScwHIWK6@bfoster/


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent cbe4134e

fs/fuse/file.c

+2 −3
Original line number Diff line number Diff line
@@ -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;