# CVE-2022-50579: linux: In the Linux kernel, the following vulnerability has been resolved:  arm64: ftrace: fix module PLTs with mcount  Li H...

CVE-2022-50579 is fixed in linux on 1 platform, first by DEBIAN-CVE-2022-50579, released October 22, 2025. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2022-50579
- Priority: Routine
- CVSS: n/a
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 22, 2025

## Description

In the Linux kernel, the following vulnerability has been resolved:  arm64: ftrace: fix module PLTs with mcount  Li Huafei reports that mcount-based ftrace with module PLTs was broken by commit:    a6253579977e4c6f ("arm64: ftrace: consistently handle PLTs.")  When a module PLTs are used and a module is loaded sufficiently far away from the kernel, we'll create PLTs for any branches which are out-of-range. These are separate from the special ftrace trampoline PLTs, which the module PLT code doesn't directly manipulate.  When mcount is in use this is a problem, as each mcount callsite in a module will be initialized to point to a module PLT, but since commit a6253579977e4c6f ftrace_make_nop() will assume that the callsite has been initialized to point to the special ftrace trampoline PLT, and ftrace_find_callable_addr() rejects other cases.  This means that when ftrace tries to initialize a callsite via ftrace_make_nop(), the call to ftrace_find_callable_addr() will find that the `_mcount` stub is out-of-range and is not handled by the ftrace PLT, resulting in a splat:  | ftrace_test: loading out-of-tree module taints kernel. | ftrace: no module PLT for _mcount | ------------[ ftrace bug ]------------ | ftrace failed to modify | [<ffff800029180014>] 0xffff800029180014 |  actual:   44:00:00:94 | Initializing ftrace call sites | ftrace record flags: 2000000 |  (0) |  expected tramp: ffff80000802eb3c | ------------[ cut here ]------------ | WARNING: CPU: 3 PID: 157 at kernel/trace/ftrace.c:2120 ftrace_bug+0x94/0x270 | Modules linked in: | CPU: 3 PID: 157 Comm: insmod Tainted: G           O       6.0.0-rc6-00151-gcd722513a189-dirty #22 | Hardware name: linux,dummy-virt (DT) | pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) | pc : ftrace_bug+0x94/0x270 | lr : ftrace_bug+0x21c/0x270 | sp : ffff80000b2bbaf0 | x29: ffff80000b2bbaf0 x28: 0000000000000000 x27: ffff0000c4d38000 | x26: 0000000000000001 x25: ffff800009d7e000 x24: ffff0000c4d86e00 | x23: 0000000002000000 x22: ffff80000a62b000 x21: ffff8000098ebea8 | x20: ffff0000c4d38000 x19: ffff80000aa24158 x18: ffffffffffffffff | x17: 0000000000000000 x16: 0a0d2d2d2d2d2d2d x15: ffff800009aa9118 | x14: 0000000000000000 x13: 6333626532303830 x12: 3030303866666666 | x11: 203a706d61727420 x10: 6465746365707865 x9 : 3362653230383030 | x8 : c0000000ffffefff x7 : 0000000000017fe8 x6 : 000000000000bff4 | x5 : 0000000000057fa8 x4 : 0000000000000000 x3 : 0000000000000001 | x2 : ad2cb14bb5438900 x1 : 0000000000000000 x0 : 0000000000000022 | Call trace: |  ftrace_bug+0x94/0x270 |  ftrace_process_locs+0x308/0x430 |  ftrace_module_init+0x44/0x60 |  load_module+0x15b4/0x1ce8 |  __do_sys_init_module+0x1ec/0x238 |  __arm64_sys_init_module+0x24/0x30 |  invoke_syscall+0x54/0x118 |  el0_svc_common.constprop.4+0x84/0x100 |  do_el0_svc+0x3c/0xd0 |  el0_svc+0x1c/0x50 |  el0t_64_sync_handler+0x90/0xb8 |  el0t_64_sync+0x15c/0x160 | ---[ end trace 0000000000000000 ]--- | ---------test_init-----------  Fix this by reverting to the old behaviour of ignoring the old instruction when initialising an mcount callsite in a module, which was the behaviour prior to commit a6253579977e4c6f.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.0.3-1 | [DEBIAN-CVE-2022-50579](https://patchblox.com/security/data/fix/linux/debian-cve-2022-50579.md) | Oct 22, 2025 |
| Linux | linux Debian 13.5 (trixie) | 6.0.3-1 | [DEBIAN-CVE-2022-50579](https://patchblox.com/security/data/fix/linux/debian-cve-2022-50579.md) | Oct 22, 2025 |
| Linux | linux Debian 14 | 6.0.3-1 | [DEBIAN-CVE-2022-50579](https://patchblox.com/security/data/fix/linux/debian-cve-2022-50579.md) | Oct 22, 2025 |

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