# CVE-2022-48914: linux: In the Linux kernel, the following vulnerability has been resolved:  xen/netfront: destroy queues before real_num_tx_...

CVE-2022-48914 is fixed in linux on 1 platform, first by DEBIAN-CVE-2022-48914, released August 22, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2022-48914
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0022
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 22, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  xen/netfront: destroy queues before real_num_tx_queues is zeroed  xennet_destroy_queues() relies on info->netdev->real_num_tx_queues to delete queues. Since d7dac083414eb5bb99a6d2ed53dc2c1b405224e5 ("net-sysfs: update the queue counts in the unregistration path"), unregister_netdev() indirectly sets real_num_tx_queues to 0. Those two facts together means, that xennet_destroy_queues() called from xennet_remove() cannot do its job, because it's called after unregister_netdev(). This results in kfree-ing queues that are still linked in napi, which ultimately crashes:      BUG: kernel NULL pointer dereference, address: 0000000000000000     #PF: supervisor read access in kernel mode     #PF: error_code(0x0000) - not-present page     PGD 0 P4D 0     Oops: 0000 [#1] PREEMPT SMP PTI     CPU: 1 PID: 52 Comm: xenwatch Tainted: G        W         5.16.10-1.32.fc32.qubes.x86_64+ #226     RIP: 0010:free_netdev+0xa3/0x1a0     Code: ff 48 89 df e8 2e e9 00 00 48 8b 43 50 48 8b 08 48 8d b8 a0 fe ff ff 48 8d a9 a0 fe ff ff 49 39 c4 75 26 eb 47 e8 ed c1 66 ff <48> 8b 85 60 01 00 00 48 8d 95 60 01 00 00 48 89 ef 48 2d 60 01 00     RSP: 0000:ffffc90000bcfd00 EFLAGS: 00010286     RAX: 0000000000000000 RBX: ffff88800edad000 RCX: 0000000000000000     RDX: 0000000000000001 RSI: ffffc90000bcfc30 RDI: 00000000ffffffff     RBP: fffffffffffffea0 R08: 0000000000000000 R09: 0000000000000000     R10: 0000000000000000 R11: 0000000000000001 R12: ffff88800edad050     R13: ffff8880065f8f88 R14: 0000000000000000 R15: ffff8880066c6680     FS:  0000000000000000(0000) GS:ffff8880f3300000(0000) knlGS:0000000000000000     CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033     CR2: 0000000000000000 CR3: 00000000e998c006 CR4: 00000000003706e0     Call Trace:      <TASK>      xennet_remove+0x13d/0x300 [xen_netfront]      xenbus_dev_remove+0x6d/0xf0      __device_release_driver+0x17a/0x240      device_release_driver+0x24/0x30      bus_remove_device+0xd8/0x140      device_del+0x18b/0x410      ? _raw_spin_unlock+0x16/0x30      ? klist_iter_exit+0x14/0x20      ? xenbus_dev_request_and_reply+0x80/0x80      device_unregister+0x13/0x60      xenbus_dev_changed+0x18e/0x1f0      xenwatch_thread+0xc0/0x1a0      ? do_wait_intr_irq+0xa0/0xa0      kthread+0x16b/0x190      ? set_kthread_struct+0x40/0x40      ret_from_fork+0x22/0x30      </TASK>  Fix this by calling xennet_destroy_queues() from xennet_uninit(), when real_num_tx_queues is still available. This ensures that queues are destroyed when real_num_tx_queues is set to 0, regardless of how unregister_netdev() was called.  Originally reported at https://github.com/QubesOS/qubes-issues/issues/7257

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.16.14-1 | [DEBIAN-CVE-2022-48914](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48914.md) | Aug 22, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.16.14-1 | [DEBIAN-CVE-2022-48914](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48914.md) | Aug 22, 2024 |
| Linux | linux Debian 14 | 5.16.14-1 | [DEBIAN-CVE-2022-48914](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48914.md) | Aug 22, 2024 |

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