Linux Kernel up to 6.6.25/6.8.4 s390 bpf_plt null pointer dereference

Summaryinfo

A vulnerability has been found in Linux Kernel up to 6.6.25/6.8.4 and classified as critical. This vulnerability affects the function bpf_plt of the component s390. Performing a manipulation results in null pointer dereference. This vulnerability is identified as CVE-2024-35917. There is not any exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.6.25/6.8.4. It has been classified as critical. This affects the function bpf_plt of the component s390. The manipulation with an unknown input leads to a null pointer dereference vulnerability. CWE is classifying the issue as CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: s390/bpf: Fix bpf_plt pointer arithmetic Kui-Feng Lee reported a crash on s390x triggered by the dummy_st_ops/dummy_init_ptr_arg test [1]: [] 0x2 [] bpf_struct_ops_test_run+0x156/0x250 [] __sys_bpf+0xa1a/0xd00 [] __s390x_sys_bpf+0x44/0x50 [] __do_syscall+0x244/0x300 [] system_call+0x70/0x98 This is caused by GCC moving memcpy() after assignments in bpf_jit_plt(), resulting in NULL pointers being written instead of the return and the target addresses. Looking at the GCC internals, the reordering is allowed because the alias analysis thinks that the memcpy() destination and the assignments' left-hand-sides are based on different objects: new_plt and bpf_plt_ret/bpf_plt_target respectively, and therefore they cannot alias. This is in turn due to a violation of the C standard: When two pointers are subtracted, both shall point to elements of the same array object, or one past the last element of the array object ... From the C's perspective, bpf_plt_ret and bpf_plt are distinct objects and cannot be subtracted. In the practical terms, doing so confuses the GCC's alias analysis. The code was written this way in order to let the C side know a few offsets defined in the assembly. While nice, this is by no means necessary. Fix the noncompliance by hardcoding these offsets. [1] https://lore.kernel.org/bpf/[email protected]/

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2024-35917 since 05/17/2024. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 6.6.26 or 6.8.5 eliminates this vulnerability. Applying the patch c3062bdb859b/d3d74e45a060/7ded842b356d is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.6.0
• 6.6.1
• 6.6.2
• 6.6.3
• 6.6.4
• 6.6.5
• 6.6.6
• 6.6.7
• 6.6.8
• 6.6.9
• 6.6.10
• 6.6.11
• 6.6.12
• 6.6.13
• 6.6.14
• 6.6.15
• 6.6.16
• 6.6.17
• 6.6.18
• 6.6.19
• 6.6.20
• 6.6.21
• 6.6.22
• 6.6.23
• 6.6.24
• 6.6.25
• 6.8.0
• 6.8.1
• 6.8.2
• 6.8.3
• 6.8.4

License

• open-source

Website

• Vendor: https://www.kernel.org/

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