Bug 1223080 (CVE-2024-26821)

Summary:	VUL-0: REJECTED: CVE-2024-26821: kernel: fs: relax mount_setattr() permission checks
Product:	[Novell Products] SUSE Security Incidents	Reporter:	SMASH SMASH <smash_bz>
Component:	Incidents	Assignee:	Security Team bot <security-team>
Status:	RESOLVED INVALID	QA Contact:	Security Team bot <security-team>
Severity:	Normal
Priority:	P3 - Medium	CC:	ailiopoulos, jack, mhocko, osalvador, rgoldwyn, thomas.leroy
Version:	unspecified
Target Milestone:	---
Hardware:	Other
OS:	Other
URL:	https://smash.suse.de/issue/402309/
Whiteboard:
Found By:	Security Response Team	Services Priority:
Business Priority:		Blocker:	---
Marketing QA Status:	---	IT Deployment:	---

Description SMASH SMASH 2024-04-18 12:56:15 UTC

In the Linux kernel, the following vulnerability has been resolved:

fs: relax mount_setattr() permission checks

When we added mount_setattr() I added additional checks compared to the
legacy do_reconfigure_mnt() and do_change_type() helpers used by regular
mount(2). If that mount had a parent then verify that the caller and the
mount namespace the mount is attached to match and if not make sure that
it's an anonymous mount.

The real rootfs falls into neither category. It is neither an anoymous
mount because it is obviously attached to the initial mount namespace
but it also obviously doesn't have a parent mount. So that means legacy
mount(2) allows changing mount properties on the real rootfs but
mount_setattr(2) blocks this. I never thought much about this but of
course someone on this planet of earth changes properties on the real
rootfs as can be seen in [1].

Since util-linux finally switched to the new mount api in 2.39 not so
long ago it also relies on mount_setattr() and that surfaced this issue
when Fedora 39 finally switched to it. Fix this.

References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2024-26821
https://www.cve.org/CVERecord?id=CVE-2024-26821
https://git.kernel.org/stable/c/2a7a31e1fb9717845d9d5e2a8c6e48848147801e
https://git.kernel.org/stable/c/31f71f2d7a081fc6c6bdf06865beedf6db5b0ca4
https://git.kernel.org/stable/c/46f5ab762d048dad224436978315cbc2fa79c630
https://git.kernel.org/stable/c/95de4ad173ca0e61034f3145d66917970961c210
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2024/CVE-2024-26821.mbox
https://bugzilla.redhat.com/show_bug.cgi?id=2275616

Comment 1 Thomas Leroy 2024-04-18 12:57:03 UTC

I'm not sure of the security implication of this one. It seems that it can only crash a booting kernel

Comment 4 Jan Kara 2024-04-19 09:00:00 UTC

Yes, this problem is of the type: New API (i.e. mount_setattr(2)) doesn't support what the old API did support (i.e. mount(2)). Thus the new API is not a complete replacement of the old API and someone actually cared so let's fix that.

I agree that there's no security implication at all.

Comment 7 Anthony Iliopoulos 2024-05-16 12:29:50 UTC

It is now rejected [1], assigning back to sec.

[1] https://lore.kernel.org/all/2024051606-imaging-entrench-b327@gregkh/

Comment 8 Thomas Leroy 2024-05-28 08:43:13 UTC

Thanks everyone for the help. Closing