[PATCH] fuse: convert page array allocation to kcalloc()

[PATCH] fuse: convert page array allocation to kcalloc()

[William Theesfeld]

fuse_get_user_pages() allocates the temporary pages[] array used by
iov_iter_extract_pages() with the open-coded kzalloc(n * sizeof(*p),
...) form.  max_pages is derived from the inbound iov_iter and is not
bounded at compile time, so the multiplication can overflow on
sufficiently large iter counts; the resulting too-small allocation
would then be written past by iov_iter_extract_pages().

Switch to kcalloc(), which carries the same zero-on-allocation
semantics and adds the standard size_mul overflow check.  No
functional change for non-overflow inputs.

Signed-off-by: William Theesfeld <william@theesfeld.net>
---
 fs/fuse/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index f94f3dc08..9e258e53a 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1586,7 +1586,7 @@ static int fuse_get_user_pages(struct fuse_args_pages *ap, struct iov_iter *ii,
 	 * manually extract pages using iov_iter_extract_pages() and then
 	 * copy that to a folios array.
 	 */
-	struct page **pages = kzalloc(max_pages * sizeof(struct page *),
+	struct page **pages = kcalloc(max_pages, sizeof(struct page *),
 				      GFP_KERNEL);
 	if (!pages) {
 		ret = -ENOMEM;
-- 
2.54.0

Re: [PATCH] fuse: convert page array allocation to kcalloc()

[Miklos Szeredi]

On Mon, 1 Jun 2026 at 21:29, William Theesfeld <william@theesfeld.net> wrote:
>
> fuse_get_user_pages() allocates the temporary pages[] array used by
> iov_iter_extract_pages() with the open-coded kzalloc(n * sizeof(*p),
> ...) form.  max_pages is derived from the inbound iov_iter and is not
> bounded at compile time, so the multiplication can overflow on
> sufficiently large iter counts; the resulting too-small allocation
> would then be written past by iov_iter_extract_pages().
>
> Switch to kcalloc(), which carries the same zero-on-allocation
> semantics and adds the standard size_mul overflow check.  No
> functional change for non-overflow inputs.
>
> Signed-off-by: William Theesfeld <william@theesfeld.net>

Applied, thanks.

Miklos