| From bippy-7c5fe7eed585 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2025-21920: vlan: enforce underlying device type |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| vlan: enforce underlying device type |
| |
| Currently, VLAN devices can be created on top of non-ethernet devices. |
| |
| Besides the fact that it doesn't make much sense, this also causes a |
| bug which leaks the address of a kernel function to usermode. |
| |
| When creating a VLAN device, we initialize GARP (garp_init_applicant) |
| and MRP (mrp_init_applicant) for the underlying device. |
| |
| As part of the initialization process, we add the multicast address of |
| each applicant to the underlying device, by calling dev_mc_add. |
| |
| __dev_mc_add uses dev->addr_len to determine the length of the new |
| multicast address. |
| |
| This causes an out-of-bounds read if dev->addr_len is greater than 6, |
| since the multicast addresses provided by GARP and MRP are only 6 |
| bytes long. |
| |
| This behaviour can be reproduced using the following commands: |
| |
| ip tunnel add gretest mode ip6gre local ::1 remote ::2 dev lo |
| ip l set up dev gretest |
| ip link add link gretest name vlantest type vlan id 100 |
| |
| Then, the following command will display the address of garp_pdu_rcv: |
| |
| ip maddr show | grep 01:80:c2:00:00:21 |
| |
| Fix the bug by enforcing the type of the underlying device during VLAN |
| device initialization. |
| |
| The Linux kernel CVE team has assigned CVE-2025-21920 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 2.6.35 with commit 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 and fixed in 5.4.291 with commit 7f1564b2b2072b7aa1ac75350e9560a07c7a44fd |
| Issue introduced in 2.6.35 with commit 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 and fixed in 5.10.235 with commit fa40ebef69234e39ec2d26930d045f2fb9a8cb2b |
| Issue introduced in 2.6.35 with commit 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 and fixed in 5.15.179 with commit 0fb7aa04c19eac4417f360a9f7611a60637bdacc |
| Issue introduced in 2.6.35 with commit 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 and fixed in 6.1.131 with commit 5a515d13e15536e82c5c7c83eb6cf5bc4827fee5 |
| Issue introduced in 2.6.35 with commit 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 and fixed in 6.6.83 with commit 3561442599804905c3defca241787cd4546e99a7 |
| Issue introduced in 2.6.35 with commit 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 and fixed in 6.12.19 with commit 30e8aee77899173a82ae5ed89f536c096f20aaeb |
| Issue introduced in 2.6.35 with commit 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 and fixed in 6.13.7 with commit b6c72479748b7ea09f53ed64b223cee6463dc278 |
| Issue introduced in 2.6.35 with commit 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 and fixed in 6.14 with commit b33a534610067ade2bdaf2052900aaad99701353 |
| |
| 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-2025-21920 |
| 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/8021q/vlan.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/7f1564b2b2072b7aa1ac75350e9560a07c7a44fd |
| https://git.kernel.org/stable/c/fa40ebef69234e39ec2d26930d045f2fb9a8cb2b |
| https://git.kernel.org/stable/c/0fb7aa04c19eac4417f360a9f7611a60637bdacc |
| https://git.kernel.org/stable/c/5a515d13e15536e82c5c7c83eb6cf5bc4827fee5 |
| https://git.kernel.org/stable/c/3561442599804905c3defca241787cd4546e99a7 |
| https://git.kernel.org/stable/c/30e8aee77899173a82ae5ed89f536c096f20aaeb |
| https://git.kernel.org/stable/c/b6c72479748b7ea09f53ed64b223cee6463dc278 |
| https://git.kernel.org/stable/c/b33a534610067ade2bdaf2052900aaad99701353 |
