Commit 6eef5092 authored by Jann Horn's avatar Jann Horn Committed by Yifan Qiao
Browse files

fuse: Initialize beyond-EOF page contents before setting uptodate 

stable inclusion
from stable-v6.6.48
commit ac42e0f0eb66af966015ee33fd355bc6f5d80cd6
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAOAMF
CVE: CVE-2024-44947

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=ac42e0f0eb66af966015ee33fd355bc6f5d80cd6

--------------------------------

commit 3c0da3d163eb32f1f91891efaade027fa9b245b9 upstream.

fuse_notify_store(), unlike fuse_do_readpage(), does not enable page
zeroing (because it can be used to change partial page contents).

So fuse_notify_store() must be more careful to fully initialize page
contents (including parts of the page that are beyond end-of-file)
before marking the page uptodate.

The current code can leave beyond-EOF page contents uninitialized, which
makes these uninitialized page contents visible to userspace via mmap().

This is an information leak, but only affects systems which do not
enable init-on-alloc (via CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y or the
corresponding kernel command line parameter).

Link: https://bugs.chromium.org/p/project-zero/issues/detail?id=2574


Cc: stable@kernel.org
Fixes: a1d75f25 ("fuse: add store request")
Signed-off-by: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarYifan Qiao <qiaoyifan4@huawei.com>
parent 43ce5700

fs/fuse/dev.c

+4 −2
Original line number Diff line number Diff line
@@ -1618,9 +1618,11 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size, 


		this_num = min_t(unsigned, num, PAGE_SIZE - offset);

		err = fuse_copy_page(cs, &page, offset, this_num, 0);

		if (!err && offset == 0 &&

		    (this_num == PAGE_SIZE || file_size == end))

		if (!PageUptodate(page) && !err && offset == 0 &&

		    (this_num == PAGE_SIZE || file_size == end)) {

			zero_user_segment(page, this_num, PAGE_SIZE);

			SetPageUptodate(page);

		}

		unlock_page(page);

		put_page(page);