| From bippy-5f407fcff5a0 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-2021-47517: ethtool: do not perform operations on net devices being unregistered |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| ethtool: do not perform operations on net devices being unregistered |
| |
| There is a short period between a net device starts to be unregistered |
| and when it is actually gone. In that time frame ethtool operations |
| could still be performed, which might end up in unwanted or undefined |
| behaviours[1]. |
| |
| Do not allow ethtool operations after a net device starts its |
| unregistration. This patch targets the netlink part as the ioctl one |
| isn't affected: the reference to the net device is taken and the |
| operation is executed within an rtnl lock section and the net device |
| won't be found after unregister. |
| |
| [1] For example adding Tx queues after unregister ends up in NULL |
| pointer exceptions and UaFs, such as: |
| |
| BUG: KASAN: use-after-free in kobject_get+0x14/0x90 |
| Read of size 1 at addr ffff88801961248c by task ethtool/755 |
| |
| CPU: 0 PID: 755 Comm: ethtool Not tainted 5.15.0-rc6+ #778 |
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/014 |
| Call Trace: |
| dump_stack_lvl+0x57/0x72 |
| print_address_description.constprop.0+0x1f/0x140 |
| kasan_report.cold+0x7f/0x11b |
| kobject_get+0x14/0x90 |
| kobject_add_internal+0x3d1/0x450 |
| kobject_init_and_add+0xba/0xf0 |
| netdev_queue_update_kobjects+0xcf/0x200 |
| netif_set_real_num_tx_queues+0xb4/0x310 |
| veth_set_channels+0x1c3/0x550 |
| ethnl_set_channels+0x524/0x610 |
| |
| The Linux kernel CVE team has assigned CVE-2021-47517 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.6 with commit 041b1c5d4a53e97fc9e029ae32469552ca12cb9b and fixed in 5.10.87 with commit 7c26da3be1e9843a15b5318f90db8a564479d2ac |
| Issue introduced in 5.6 with commit 041b1c5d4a53e97fc9e029ae32469552ca12cb9b and fixed in 5.15.8 with commit cfd719f04267108f5f5bf802b9d7de69e99a99f9 |
| Issue introduced in 5.6 with commit 041b1c5d4a53e97fc9e029ae32469552ca12cb9b and fixed in 5.16 with commit dde91ccfa25fd58f64c397d91b81a4b393100ffa |
| |
| 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-2021-47517 |
| 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/ethtool/netlink.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/7c26da3be1e9843a15b5318f90db8a564479d2ac |
| https://git.kernel.org/stable/c/cfd719f04267108f5f5bf802b9d7de69e99a99f9 |
| https://git.kernel.org/stable/c/dde91ccfa25fd58f64c397d91b81a4b393100ffa |
