Integer Overflow or Wraparound Affecting kernel-rt-debug-devel-matched package, versions *


Severity

Recommended
low

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.04% (6th percentile)

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  • Snyk IDSNYK-RHEL9-KERNELRTDEBUGDEVELMATCHED-8261113
  • published23 Oct 2024
  • disclosed21 Oct 2024

Introduced: 21 Oct 2024

CVE-2024-47702  (opens in a new tab)
CWE-190  (opens in a new tab)

How to fix?

There is no fixed version for RHEL:9 kernel-rt-debug-devel-matched.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-debug-devel-matched package and not the kernel-rt-debug-devel-matched package as distributed by RHEL. See How to fix? for RHEL:9 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/

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