CVE-2021-47285: net/nfc/rawsock.c: fix a permission check bug

CVE-2021-47285: net/nfc/rawsock.c: fix a permission check bug

[Greg Kroah-Hartman]

Description
===========

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

net/nfc/rawsock.c: fix a permission check bug

The function rawsock_create() calls a privileged function sk_alloc(), which requires a ns-aware check to check net->user_ns, i.e., ns_capable(). However, the original code checks the init_user_ns using capable(). So we replace the capable() with ns_capable().

The Linux kernel CVE team has assigned CVE-2021-47285 to this issue.


Affected and fixed versions
===========================

	Fixed in 4.4.273 with commit c08e0be44759
	Fixed in 4.9.273 with commit d6a21a3fb033
	Fixed in 4.14.237 with commit 38cb2e23188a
	Fixed in 4.19.195 with commit ec72482564ff
	Fixed in 5.4.126 with commit f3ed12af6bbb
	Fixed in 5.10.44 with commit 1e5cab50208c
	Fixed in 5.12.11 with commit 90d0a3c76965
	Fixed in 5.13 with commit 8ab78863e9ef

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47285
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/nfc/rawsock.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/c08e0be44759d0b5affc5888be4aa5e536873335
	https://git.kernel.org/stable/c/d6a21a3fb03300fbaa9fc3ed99f8b0962ce28362
	https://git.kernel.org/stable/c/38cb2e23188af29c43966acee9dbb18b62e26cfe
	https://git.kernel.org/stable/c/ec72482564ff99c6832d33610d9f8ab7ecc81b6d
	https://git.kernel.org/stable/c/f3ed12af6bbbaf79eddb0ae14656b8ecacea74f0
	https://git.kernel.org/stable/c/1e5cab50208c8fb7351b798cb1d569debfeb994a
	https://git.kernel.org/stable/c/90d0a3c76965d7a10fc87c07be3e9714e2130d5c
	https://git.kernel.org/stable/c/8ab78863e9eff11910e1ac8bcf478060c29b379e

Re: CVE-2021-47285: net/nfc/rawsock.c: fix a permission check bug

[Michal Koutný]

[-- Attachment #1: Type: text/plain, Size: 1045 bytes --]

Hello.

On Tue, May 21, 2024 at 04:20:39PM GMT, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> In the Linux kernel, the following vulnerability has been resolved:
> 
> net/nfc/rawsock.c: fix a permission check bug
> 
> The function rawsock_create() calls a privileged function sk_alloc(), which requires a ns-aware check to check net->user_ns, i.e., ns_capable(). However, the original code checks the init_user_ns using capable(). So we replace the capable() with ns_capable().
> 
> The Linux kernel CVE team has assigned CVE-2021-47285 to this issue.
> ...
> 	https://git.kernel.org/stable/c/8ab78863e9eff11910e1ac8bcf478060c29b379e

Despite the patch changes guard related to EPERM bailout, it actually
swaps a "stronger" predicate capable() for a "weaker" ns_capable().

Without the patch, an unprivilged user is not allowed to create nfc
SOCK_RAW inside owned netns, with the patch, it's allowed.

That's a functional change but not security related. Or have I missed a
negation somewhere?

Thanks,
Michal

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

Re: CVE-2021-47285: net/nfc/rawsock.c: fix a permission check bug

[Greg Kroah-Hartman]

On Tue, Jul 02, 2024 at 06:15:09PM +0200, Michal Koutný wrote:
> Hello.
> 
> On Tue, May 21, 2024 at 04:20:39PM GMT, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> > In the Linux kernel, the following vulnerability has been resolved:
> > 
> > net/nfc/rawsock.c: fix a permission check bug
> > 
> > The function rawsock_create() calls a privileged function sk_alloc(), which requires a ns-aware check to check net->user_ns, i.e., ns_capable(). However, the original code checks the init_user_ns using capable(). So we replace the capable() with ns_capable().
> > 
> > The Linux kernel CVE team has assigned CVE-2021-47285 to this issue.
> > ...
> > 	https://git.kernel.org/stable/c/8ab78863e9eff11910e1ac8bcf478060c29b379e
> 
> Despite the patch changes guard related to EPERM bailout, it actually
> swaps a "stronger" predicate capable() for a "weaker" ns_capable().
> 
> Without the patch, an unprivilged user is not allowed to create nfc
> SOCK_RAW inside owned netns, with the patch, it's allowed.

Ah, we misread this, thinking it went up in security, not "down".

And this was from the old GSD ids, odd that no one noticed it then :(

Anyway, now rejected, thanks for the review!

greg k-h