af_packet: fix integer overflow in prb_calc_retire_blk_tmo()

Description

In the Linux kernel, the following vulnerability has been resolved: af_packet: fix integer overflow in prb_calc_retire_blk_tmo() prb_calc_retire_blk_tmo() computes in 32-bit int arithmetic: mbits = (blk_size_in_bytes * 8) / (1024 * 1024); If I'm reading the validation right, tp_block_size is user controlled and packet_set_ring() only rejects values that are <= 0 as int or not page aligned, so a 256MiB block goes right through (and alloc_one_pg_vec_page() even has a vzalloc fallback for it). 0x10000000 * 8 wraps to INT_MIN, and on a NIC reporting 1 Gbps (div == 1) the function ends up returning -2047. The condition is actually (8 * size) mod 2^32 >= 2^31 && div == 1, so the trigger set is [256,512), [768,1024), [1280,1536) and [1792,2048) MiB. Other sizes wrap to non-negative values and faster links divide the unsigned value back below 2^31, which is why this doesn't blow up for everyone. What makes it fatal is what happens next in init_prb_bdqc(): p1->interval_ktime = ms_to_ktime(prb_calc_retire_blk_tmo(...)); hrtimer_start(&p1->retire_blk_timer, p1->interval_ktime, HRTIMER_MODE_REL_SOFT); A negative relative timeout expires immediately. The callback unconditionally returns HRTIMER_RESTART, and hrtimer_forward() turns the negative interval into hrtimer_resolution: if (interval < hrtimer_resolution) interval = hrtimer_resolution; So the SOFT timer re-fires at the maximum rate forever, holding sk_receive_queue.lock each pass. One CPU spins in softirq until the socket is closed. Repeat with more rings and the machine is gone. The overflow itself is ancient - it was introduced together with TPACKET_V3 in f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation."). Its effect prior to f7460d2989fa ("net: af_packet: Use hrtimer to do the retire operation", v6.18) was not as clear-cut, though: the return value was stored into an unsigned short retire_blk_tov, so a negative result was truncated, and a 0-jiffy delay loop could be programmed as well. Neither is nearly as detrimental as the immediate maximum-rate spin the hrtimer conversion turned it into. (Unrelated to CVE-2019-20812 - that one was the ethtool failure path returning 0, which now returns DEFAULT_PRB_RETIRE_TOV.) Reproducer, needs CAP_NET_RAW (a --network host container has it by default) and a 1 Gbps NIC (QEMU e1000 works): int fd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); bind(fd, ...); int v = TPACKET_V3; setsockopt(fd, SOL_PACKET, PACKET_VERSION, &v, sizeof(v)); struct tpacket_req3 req = { .tp_block_size = 0x10000000, .tp_block_nr = 1, .tp_frame_size = 2048, .tp_frame_nr = 0x10000000 / 2048, .tp_retire_blk_tov = 0, }; setsockopt(fd, SOL_PACKET, PACKET_RX_RING, &req, sizeof(req)); Compute in 64 bits instead. The operands are already bounded by the existing validation, so nothing else changes. If you'd prefer a different fix, just say so and I'll respin.

Timeline

Scores

No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Received.

EPSS (exploitation in 30 days)

0.22% · top 88% of all CVEs (11 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.

Affected products

• Linux · Linux

  • affected f6fb8f100b807378fda19e83e5ac6828b638603a – < 02afd75649a4e001031ed82153a5c39312ec0737
  • affected f6fb8f100b807378fda19e83e5ac6828b638603a – < eb5b3838b9200dac04bfe33483db0ee8287456fb
  • affected f6fb8f100b807378fda19e83e5ac6828b638603a – < 297acc571d5813db76b147c745b91031d5f9c960
  • affected f6fb8f100b807378fda19e83e5ac6828b638603a – < be1aacff399d519cc48d6b34354a54dd79041140
  • affected f6fb8f100b807378fda19e83e5ac6828b638603a – < b2bcc6a254d6f27823a56787668ae4ee8cdb6e71
  • affected f6fb8f100b807378fda19e83e5ac6828b638603a – < 6279211e7d2456ecd195d236c9ee5e5c6fa5a17a
  • affected f6fb8f100b807378fda19e83e5ac6828b638603a – < 218a944b9e035d4b47d59c69af6ca13319da15fb
  • affected f6fb8f100b807378fda19e83e5ac6828b638603a – < 56d82862a0a243ac14ba11b6d7b57ddc2d064b95

• Linux · Linux

  • affected 3.2
  • unaffected < 3.2
  • unaffected 5.10.271 – ≤ 5.10.*
  • unaffected 5.15.222 – ≤ 5.15.*
  • unaffected 6.1.189 – ≤ 6.1.*
  • unaffected 6.6.158 – ≤ 6.6.*
  • unaffected 6.12.112 – ≤ 6.12.*
  • unaffected 6.18.55 – ≤ 6.18.*
  • unaffected 7.2.9 – ≤ 7.2.*
  • unaffected 7.3 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-103592 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-98547](https://cveledger.app/badge/CVE-2026-98547.svg)](https://cveledger.app/cve/CVE-2026-98547)

Record last updated 19 Oct 2026, 09:21 UTC.