| 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-2024-55916: Drivers: hv: util: Avoid accessing a ringbuffer not initialized yet |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| Drivers: hv: util: Avoid accessing a ringbuffer not initialized yet |
| |
| If the KVP (or VSS) daemon starts before the VMBus channel's ringbuffer is |
| fully initialized, we can hit the panic below: |
| |
| hv_utils: Registering HyperV Utility Driver |
| hv_vmbus: registering driver hv_utils |
| ... |
| BUG: kernel NULL pointer dereference, address: 0000000000000000 |
| CPU: 44 UID: 0 PID: 2552 Comm: hv_kvp_daemon Tainted: G E 6.11.0-rc3+ #1 |
| RIP: 0010:hv_pkt_iter_first+0x12/0xd0 |
| Call Trace: |
| ... |
| vmbus_recvpacket |
| hv_kvp_onchannelcallback |
| vmbus_on_event |
| tasklet_action_common |
| tasklet_action |
| handle_softirqs |
| irq_exit_rcu |
| sysvec_hyperv_stimer0 |
| </IRQ> |
| <TASK> |
| asm_sysvec_hyperv_stimer0 |
| ... |
| kvp_register_done |
| hvt_op_read |
| vfs_read |
| ksys_read |
| __x64_sys_read |
| |
| This can happen because the KVP/VSS channel callback can be invoked |
| even before the channel is fully opened: |
| 1) as soon as hv_kvp_init() -> hvutil_transport_init() creates |
| /dev/vmbus/hv_kvp, the kvp daemon can open the device file immediately and |
| register itself to the driver by writing a message KVP_OP_REGISTER1 to the |
| file (which is handled by kvp_on_msg() ->kvp_handle_handshake()) and |
| reading the file for the driver's response, which is handled by |
| hvt_op_read(), which calls hvt->on_read(), i.e. kvp_register_done(). |
| |
| 2) the problem with kvp_register_done() is that it can cause the |
| channel callback to be called even before the channel is fully opened, |
| and when the channel callback is starting to run, util_probe()-> |
| vmbus_open() may have not initialized the ringbuffer yet, so the |
| callback can hit the panic of NULL pointer dereference. |
| |
| To reproduce the panic consistently, we can add a "ssleep(10)" for KVP in |
| __vmbus_open(), just before the first hv_ringbuffer_init(), and then we |
| unload and reload the driver hv_utils, and run the daemon manually within |
| the 10 seconds. |
| |
| Fix the panic by reordering the steps in util_probe() so the char dev |
| entry used by the KVP or VSS daemon is not created until after |
| vmbus_open() has completed. This reordering prevents the race condition |
| from happening. |
| |
| The Linux kernel CVE team has assigned CVE-2024-55916 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 4.9 with commit e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c and fixed in 5.4.289 with commit f091a224a2c82f1e302b1768d73bb6332f687321 |
| Issue introduced in 4.9 with commit e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c and fixed in 5.10.233 with commit d81f4e73aff9b861671df60e5100ad25cc16fbf8 |
| Issue introduced in 4.9 with commit e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c and fixed in 5.15.176 with commit 042253c57be901bfd19f15b68267442b70f510d5 |
| Issue introduced in 4.9 with commit e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c and fixed in 6.1.122 with commit 718fe694a334be9d1a89eed22602369ac18d6583 |
| Issue introduced in 4.9 with commit e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c and fixed in 6.6.68 with commit 89fcec5e466b3ac9b376e0d621c71effa1a7983f |
| Issue introduced in 4.9 with commit e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c and fixed in 6.12.7 with commit 3dd7a30c6d7f90afcf19e9b072f572ba524d7ec6 |
| Issue introduced in 4.9 with commit e0fa3e5e7df61eb2c339c9f0067c202c0cdeec2c and fixed in 6.13 with commit 07a756a49f4b4290b49ea46e089cbe6f79ff8d26 |
| |
| 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-2024-55916 |
| 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: |
| drivers/hv/hv_kvp.c |
| drivers/hv/hv_snapshot.c |
| drivers/hv/hv_util.c |
| drivers/hv/hyperv_vmbus.h |
| include/linux/hyperv.h |
| |
| |
| 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/f091a224a2c82f1e302b1768d73bb6332f687321 |
| https://git.kernel.org/stable/c/d81f4e73aff9b861671df60e5100ad25cc16fbf8 |
| https://git.kernel.org/stable/c/042253c57be901bfd19f15b68267442b70f510d5 |
| https://git.kernel.org/stable/c/718fe694a334be9d1a89eed22602369ac18d6583 |
| https://git.kernel.org/stable/c/89fcec5e466b3ac9b376e0d621c71effa1a7983f |
| https://git.kernel.org/stable/c/3dd7a30c6d7f90afcf19e9b072f572ba524d7ec6 |
| https://git.kernel.org/stable/c/07a756a49f4b4290b49ea46e089cbe6f79ff8d26 |
