# CVE-2022-48983: linux: In the Linux kernel, the following vulnerability has been resolved:  io_uring: Fix a null-ptr-deref in io_tctx_exit_c...

CVE-2022-48983 is fixed in linux on 1 platform, first by DEBIAN-CVE-2022-48983, released October 21, 2024. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2022-48983
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0026
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 21, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  io_uring: Fix a null-ptr-deref in io_tctx_exit_cb()  Syzkaller reports a NULL deref bug as follows:   BUG: KASAN: null-ptr-deref in io_tctx_exit_cb+0x53/0xd3  Read of size 4 at addr 0000000000000138 by task file1/1955   CPU: 1 PID: 1955 Comm: file1 Not tainted 6.1.0-rc7-00103-gef4d3ea40565 #75  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014  Call Trace:   <TASK>   dump_stack_lvl+0xcd/0x134   ? io_tctx_exit_cb+0x53/0xd3   kasan_report+0xbb/0x1f0   ? io_tctx_exit_cb+0x53/0xd3   kasan_check_range+0x140/0x190   io_tctx_exit_cb+0x53/0xd3   task_work_run+0x164/0x250   ? task_work_cancel+0x30/0x30   get_signal+0x1c3/0x2440   ? lock_downgrade+0x6e0/0x6e0   ? lock_downgrade+0x6e0/0x6e0   ? exit_signals+0x8b0/0x8b0   ? do_raw_read_unlock+0x3b/0x70   ? do_raw_spin_unlock+0x50/0x230   arch_do_signal_or_restart+0x82/0x2470   ? kmem_cache_free+0x260/0x4b0   ? putname+0xfe/0x140   ? get_sigframe_size+0x10/0x10   ? do_execveat_common.isra.0+0x226/0x710   ? lockdep_hardirqs_on+0x79/0x100   ? putname+0xfe/0x140   ? do_execveat_common.isra.0+0x238/0x710   exit_to_user_mode_prepare+0x15f/0x250   syscall_exit_to_user_mode+0x19/0x50   do_syscall_64+0x42/0xb0   entry_SYSCALL_64_after_hwframe+0x63/0xcd  RIP: 0023:0x0  Code: Unable to access opcode bytes at 0xffffffffffffffd6.  RSP: 002b:00000000fffb7790 EFLAGS: 00000200 ORIG_RAX: 000000000000000b  RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000  RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000  RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000  R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000  R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000   </TASK>  Kernel panic - not syncing: panic_on_warn set ...  This happens because the adding of task_work from io_ring_exit_work() isn't synchronized with canceling all work items from eg exec. The execution of the two are ordered in that they are both run by the task itself, but if io_tctx_exit_cb() is queued while we're canceling all work items off exec AND gets executed when the task exits to userspace rather than in the main loop in io_uring_cancel_generic(), then we can find current->io_uring == NULL and hit the above crash.  It's safe to add this NULL check here, because the execution of the two paths are done by the task itself.  [axboe: add code comment and also put an explanation in the commit msg]

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.4-1 | [DEBIAN-CVE-2022-48983](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48983.md) | Oct 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 6.1.4-1 | [DEBIAN-CVE-2022-48983](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48983.md) | Oct 21, 2024 |
| Linux | linux Debian 14 | 6.1.4-1 | [DEBIAN-CVE-2022-48983](https://patchblox.com/security/data/fix/linux/debian-cve-2022-48983.md) | Oct 21, 2024 |

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