CVE-2023-53669

In the Linux kernel, the following vulnerability has been resolved:

tcp: fix skb_copy_ubufs() vs BIG TCP

David Ahern reported crashes in skb_copy_ubufs() caused by TCP tx zerocopy using hugepages, and skb length bigger than ~68 KB.

skb_copy_ubufs() assumed it could copy all payload using up to MAX_SKB_FRAGS order-0 pages.

This assumption broke when BIG TCP was able to put up to 512 KB per skb.

We did not hit this bug at Google because we use CONFIG_MAX_SKB_FRAGS=45 and limit gso_max_size to 180000.

A solution is to use higher order pages if needed.

v2: add missing __GFP_COMP, or we leak memory.

The bug could happen in skb_copy_ubufs() when BIG TCP allows very large skbs (e.g., ~512 KB) and TCP TX zerocopy with hugepages is used. Leads to Kernel Panic under specific, non-default conditions: BIG TCP/gso_max_size configured large, zerocopy transmit enabled, and traffic producing >64 KB skbs. The impact level likely only DOS, but theoretically could be used for privileges escalation, so for the CVSS keeping higher range value CIA:LLH.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.