Linux: Use After Free
CVE-2024-41070 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions be847bb20c809de8ac124431b556f244400b0491, 4cdf6926f443c84f680213c7aafbe6f91a5fcbc0, b26c8c85463ef27a522d24fcd05651f0bb039e47 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.23% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to be847bb20c809de8ac124431b556f244400b0491 or 4cdf6926f443c84f680213c7aafbe6f91a5fcbc0 or b26c8c85463ef27a522d24fcd05651f0bb039e47 or 5f856023971f97fff74cfaf21b48ec320147b50a, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.4.281 or 5.10.223 or 5.15.164 or 6.1.101, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 121f80ba68f1a5779a36d7b3247206e60e0a7418 up to, but not including, be847bb20c809de8ac124431b556f244400b0491; 121f80ba68f1a5779a36d7b3247206e60e0a7418 up to, but not including, 4cdf6926f443c84f680213c7aafbe6f91a5fcbc0; 121f80ba68f1a5779a36d7b3247206e60e0a7418 up to, but not including, b26c8c85463ef27a522d24fcd05651f0bb039e47; 121f80ba68f1a5779a36d7b3247206e60e0a7418 up to, but not including, 5f856023971f97fff74cfaf21b48ec320147b50a; 121f80ba68f1a5779a36d7b3247206e60e0a7418 up to, but not including, 82c7a4cf14aa866f8f7f09e662b02eddc49ee0bf; 121f80ba68f1a5779a36d7b3247206e60e0a7418 up to, but not including, 9975f93c760a32453d7639cf6fcf3f73b4e71ffe; 121f80ba68f1a5779a36d7b3247206e60e0a7418 up to, but not including, a986fa57fd81a1430e00b3c6cf8a325d6f894a63; 4.12 | be847bb20c809de8ac124431b556f244400b0491, 4cdf6926f443c84f680213c7aafbe6f91a5fcbc0, b26c8c85463ef27a522d24fcd05651f0bb039e47, 5f856023971f97fff74cfaf21b48ec320147b50a, 82c7a4cf14aa866f8f7f09e662b02eddc49ee0bf, 9975f93c760a32453d7639cf6fcf3f73b4e71ffe |
| Linux | Linux Kernel | before 5.4.281; 5.5 up to, but not including, 5.10.223; 5.11 up to, but not including, 5.15.164; 5.16 up to, but not including, 6.1.101; 6.2 up to, but not including, 6.6.42; 6.7 up to, but not including, 6.9.11 | 5.4.281, 5.10.223, 5.15.164, 6.1.101, 6.6.42, 6.9.11 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: KVM: PPC: Book3S HV: Prevent UAF in kvm_spapr_tce_attach_iommu_group() Al reported a possible use-after-free (UAF) in kvm_spapr_tce_attach_iommu_group(). It looks up `stt` from tablefd, but then continues to use it after doing fdput() on the returned fd. After the fdput() the tablefd is free to be closed by another thread. The close calls kvm_spapr_tce_release() and then release_spapr_tce_table() (via call_rcu()) which frees `stt`. Although there are calls to rcu_read_lock() in kvm_spapr_tce_attach_iommu_group() they are not sufficient to prevent the UAF, because `stt` is used outside the locked regions. With an artifcial delay after the fdput() and a userspace program which triggers the race, KASAN detects the UAF: BUG: KASAN: slab-use-after-free in kvm_spapr_tce_attach_iommu_group+0x298/0x720 [kvm] Read of size 4 at addr c000200027552c30 by task kvm-vfio/2505 CPU: 54 PID: 2505 Comm: kvm-vfio Not tainted 6.10.0-rc3-next-20240612-dirty #1 Hardware name: 8335-GTH POWER9 0x4e1202 opal:skiboot-v6.5.3-35-g1851b2a06 PowerNV Call Trace: dump_stack_lvl+0xb4/0x108 (unreliable) print_report+0x2b4/0x6ec kasan_report+0x118/0x2b0 __asan_load4+0xb8/0xd0 kvm_spapr_tce_attach_iommu_group+0x298/0x720 [kvm] kvm_vfio_set_attr+0x524/0xac0 [kvm] kvm_device_ioctl+0x144/0x240 [kvm] sys_ioctl+0x62c/0x1810 system_call_exception+0x190/0x440 system_call_vectored_common+0x15c/0x2ec ... Freed by task 0: ... kfree+0xec/0x3e0 release_spapr_tce_table+0xd4/0x11c [kvm] rcu_core+0x568/0x16a0 handle_softirqs+0x23c/0x920 do_softirq_own_stack+0x6c/0x90 do_softirq_own_stack+0x58/0x90 __irq_exit_rcu+0x218/0x2d0 irq_exit+0x30/0x80 arch_local_irq_restore+0x128/0x230 arch_local_irq_enable+0x1c/0x30 cpuidle_enter_state+0x134/0x5cc cpuidle_enter+0x6c/0xb0 call_cpuidle+0x7c/0x100 do_idle+0x394/0x410 cpu_startup_entry+0x60/0x70 start_secondary+0x3fc/0x410 start_secondary_prolog+0x10/0x14 Fix it by delaying the fdput() until `stt` is no longer in use, which is effectively the entire function. To keep the patch minimal add a call to fdput() at each of the existing return paths. Future work can convert the function to goto or __cleanup style cleanup. With the fix in place the test case no longer triggers the UAF.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/4cdf6926f443c84f680213c7aafbe6f91a5fcbc0
- git.kernel.org/stable/c/5f856023971f97fff74cfaf21b48ec320147b50a
- git.kernel.org/stable/c/82c7a4cf14aa866f8f7f09e662b02eddc49ee0bf
- git.kernel.org/stable/c/9975f93c760a32453d7639cf6fcf3f73b4e71ffe
- git.kernel.org/stable/c/a986fa57fd81a1430e00b3c6cf8a325d6f894a63
- git.kernel.org/stable/c/b26c8c85463ef27a522d24fcd05651f0bb039e47
- git.kernel.org/stable/c/be847bb20c809de8ac124431b556f244400b0491
Other references
Recent Use After Free vulnerabilities
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