From: Bernd Schubert <bschubert@ddn.com> In fuse_get_user_pages(), set *nbytesp to 0 when struct page **pages allocation fails. This prevents the caller (fuse_direct_io) from making incorrect assumptions that could lead to NULL pointer dereferences when processing the request reply. Previously, *nbytesp was left unmodified on allocation failure, which could cause issues if the caller assumed pages had been added to ap->descs[] when they hadn't. Reported-by: syzbot+87b8e6ed25dbc41759f7@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=87b8e6ed25dbc41759f7 Fixes: 3b97c3652d91 ("fuse: convert direct io to use folios") Signed-off-by: Bernd Schubert <bschubert@ddn.com> Reviewed-by: Joanne Koong <joannelkoong@gmail.com> Tested-by: Dmitry Antipov <dmantipov@yandex.ru> Tested-by: David Howells <dhowells@redhat.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> --- fs/fuse/file.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index a1bf0ad5ffeb..f25874a4b5de 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1460,8 +1460,10 @@ static int fuse_get_user_pages(struct fuse_args_pages *ap, struct iov_iter *ii, */ struct page **pages = kzalloc(max_pages * sizeof(struct page *), GFP_KERNEL); - if (!pages) - return -ENOMEM; + if (!pages) { + ret = -ENOMEM; + goto out; + } while (nbytes < *nbytesp && nr_pages < max_pages) { unsigned nfolios, i; @@ -1507,6 +1509,7 @@ static int fuse_get_user_pages(struct fuse_args_pages *ap, struct iov_iter *ii, else ap->args.out_pages = true; +out: *nbytesp = nbytes; return ret < 0 ? ret : 0; -- 2.46.1