From 78f2560fc9fa5ccaaf23ac78edb732c08bad7a92 Mon Sep 17 00:00:00 2001 From: Bernd Schubert Date: Tue, 3 Dec 2024 00:01:10 +0100 Subject: [PATCH] fuse: Set *nbytesp=0 in fuse_get_user_pages on allocation failure 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 Reviewed-by: Joanne Koong Tested-by: Dmitry Antipov Tested-by: David Howells Signed-off-by: Miklos Szeredi --- 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 15b08d6a5739..7d92a5479998 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1541,8 +1541,10 @@ 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; @@ -1588,6 +1590,7 @@ 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; -- 2.50.1