CVE-2024-47702 Affecting kernel-azure package, versions <6.4.0-150600.8.17.2
Threat Intelligence
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Test your applications- Snyk IDSNYK-SLES156-KERNELAZURE-8378253
- published14 Nov 2024
- disclosed13 Nov 2024
Introduced: 13 Nov 2024
CVE-2024-47702 (opens in a new tab)How to fix?
Upgrade SLES:15.6 kernel-azure to version 6.4.0-150600.8.17.2 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-azure package and not the kernel-azure package as distributed by SLES.
See How to fix? for SLES:15.6 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fail verification for sign-extension of packet data/data_end/data_meta
syzbot reported a kernel crash due to commit 1f1e864b6555 ("bpf: Handle sign-extenstin ctx member accesses"). The reason is due to sign-extension of 32-bit load for packet data/data_end/data_meta uapi field.
The original code looks like: r2 = *(s32 )(r1 + 76) / load __sk_buff->data */ r3 = *(u32 )(r1 + 80) / load __sk_buff->data_end */ r0 = r2 r0 += 8 if r3 > r0 goto +1 ... Note that __sk_buff->data load has 32-bit sign extension.
After verification and convert_ctx_accesses(), the final asm code looks like: r2 = *(u64 *)(r1 +208) r2 = (s32)r2 r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 > r0 goto pc+1 ... Note that 'r2 = (s32)r2' may make the kernel __sk_buff->data address invalid which may cause runtime failure.
Currently, in C code, typically we have void *data = (void *)(long)skb->data; void *data_end = (void *)(long)skb->data_end; ... and it will generate r2 = *(u64 *)(r1 +208) r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 > r0 goto pc+1
If we allow sign-extension, void *data = (void *)(long)(int)skb->data; void *data_end = (void *)(long)skb->data_end; ... the generated code looks like r2 = *(u64 *)(r1 +208) r2 <<= 32 r2 s>>= 32 r3 = *(u64 *)(r1 +80) r0 = r2 r0 += 8 if r3 > r0 goto pc+1 and this will cause verification failure since "r2 <<= 32" is not allowed as "r2" is a packet pointer.
To fix this issue for case r2 = *(s32 )(r1 + 76) / load __sk_buff->data */ this patch added additional checking in is_valid_access() callback function for packet data/data_end/data_meta access. If those accesses are with sign-extenstion, the verification will fail.
[1] https://lore.kernel.org/bpf/000000000000c90eee061d236d37@google.com/
References
- https://www.suse.com/security/cve/CVE-2024-47702.html
- https://bugzilla.suse.com/1231924
- https://git.kernel.org/stable/c/92de36080c93296ef9005690705cba260b9bd68a
- https://git.kernel.org/stable/c/f09757fe97a225ae505886eac572e4cbfba96537
- https://git.kernel.org/stable/c/f1620c93a1ec950d87ef327a565d3907736d3340