net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 6.6.160, 6.12.110, 6.18.52, 7.2.6
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
In the Linux kernel, the following vulnerability has been resolved: net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue gred_enqueue(), bfifo_enqueue() and plug_enqueue() admit a packet when the current backlog plus the packet length fits within the queue limit: sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit (gred default VQ) gred_backlog+qdisc_pkt_len(skb) <= q->limit (gred configured VQ) sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit (bfifo) sch->qstats.backlog + skb->len <= q->limit (plug) sch->qstats.backlog and q->backlog are u32, and qdisc_pkt_len()/skb->len are unsigned int, so all sums are computed in 32 bits and wrap at 2^32. Once the true backlog exceeds 4 GiB the wrapped sum becomes small and admission keeps succeeding, so the queue grows without bound and the kernel can be driven to OOM. Promote the sums to u64 so admission stops once the true backlog exceeds the limit. The limit is u32, so the bounded queue stays below 2^32 and the stored u32 backlog never wraps. The bug can only be reproduced as root (albeit with ridiculous setup): attach a gred (or bfifo/plug) qdisc with a limit near 4 GiB, leaving the default VQ unconfigured (for gred), and drive >4 GiB of queued traffic (e.g. via a size table / stab to inflate qdisc_pkt_len, or sustained high-rate traffic). The u32 backlog+len sum wraps at 2^32, admission keeps succeeding, and the queue grows unboundedly to OOM.
Timeline
- CVE published
- Record last updated
Affected versions
- Linux Linux
From a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8 · fixed in c5ca77024812563fe15c4f7aa906791c3683e9fd; From a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8 · fixed in 3fb51b3960342bbee563543f8d33710fd0fb5a96; From a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8 · fixed in 8b2d8c70b969bf84f9e248bfaf2a7135129f2eb6; From a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8 · fixed in d98b92f3d57976ae185238946ec5ea0be32195aa; From a3eb95f891d6130b1fc03dd07a8b54cf0a5c8ab8 · fixed in 4c660ee8c809637909f4f7eb1017f7b9401c75c4
- Linux Linux
4.2
- KernelLinux
From 4.2.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.110; From 6.13.0 · fixed in 6.18.52; From 6.19.0 · fixed in 7.2.6