pfifo_tail_enqueue: Drop new packet when sch->limit == 0
In the Linux kernel, the following vulnerability has been resolved: pfifo_tail_enqueue: Drop new packet when sch->limit == 0 Expected behaviour: In case we reach scheduler's limit, pfifo_tail_enqueue() will drop a packet in scheduler's queue and decrease scheduler's qlen by one. Then, pfifo_tail_enqueue() enqueue new packet and increase scheduler's qlen by one. Finally, pfifo_tail_enqueue() return `NET_XMIT_CN` status code. Weird behaviour: In case we set `sch->limit == 0` and trigger pfifo_tail_enqueue() on a scheduler that has no packet, the 'drop a packet' step will do nothing. This means the scheduler's qlen still has value equal 0. Then, we continue to enqueue new packet and increase scheduler's qlen by one. In summary, we can leverage pfifo_tail_enqueue() to increase qlen by one and return `NET_XMIT_CN` status code. The problem is: Let's say we have two qdiscs: Qdisc_A and Qdisc_B. - Qdisc_A's type must have '->graft()' function to create parent/child relationship. Let's say Qdisc_A's type is `hfsc`. Enqueue packet to this qdisc will trigger `hfsc_enqueue`. - Qdisc_B's type is pfifo_head_drop. Enqueue packet to this qdisc will trigger `pfifo_tail_enqueue`. - Qdisc_B is configured to have `sch->limit == 0`. - Qdisc_A is configured to route the enqueued's packet to Qdisc_B. Enqueue packet through Qdisc_A will lead to: - hfsc_enqueue(Qdisc_A) -> pfifo_tail_enqueue(Qdisc_B) - Qdisc_B->q.qlen += 1 - pfifo_tail_enqueue() return `NET_XMIT_CN` - hfsc_enqueue() check for `NET_XM
CVE-2025-21702
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2025-21702
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "57dbb2d83d100ea601c54fe129bfde0678db5dee",
"lessThan": "78285b53266d6d51fa4ff504a23df03852eba84e",
"versionType": "git"
},
{
"status": "affected",
"version": "57dbb2d83d100ea601c54fe129bfde0678db5dee",
"lessThan": "7a9723ec27aff5674f1fd4934608937f1d650980",
"versionType": "git"
},
{
"status": "affected",
"version": "57dbb2d83d100ea601c54fe129bfde0678db5dee",
"lessThan": "a56a6e8589a9b98d8171611fbcc1e45a15fd2455",
"versionType": "git"
},
{
"status": "affected",
"version": "57dbb2d83d100ea601c54fe129bfde0678db5dee",
"lessThan": "020ecb76812a0526f4130ab5aeb6dc7c773e7ab9",
"versionType": "git"
},
{
"status": "affected",
"version": "57dbb2d83d100ea601c54fe129bfde0678db5dee",
"lessThan": "79a955ea4a2e5ddf4a36328959de0de496419888",
"versionType": "git"
},
{
"status": "affected",
"version": "57dbb2d83d100ea601c54fe129bfde0678db5dee",
"lessThan": "e40cb34b7f247fe2e366fd192700d1b4f38196ca",
"versionType": "git"
},
{
"status": "affected",
"version": "57dbb2d83d100ea601c54fe129bfde0678db5dee",
"lessThan": "b6a079c3b6f95378f26e2aeda520cb3176f7067b",
"versionType": "git"
},
{
"status": "affected",
"version": "57dbb2d83d100ea601c54fe129bfde0678db5dee",
"lessThan": "647cef20e649c576dff271e018d5d15d998b629d",
"versionType": "git"
}
],
"programFiles": [
"net/sched/sch_fifo.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.34"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "2.6.34",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.4.291",
"versionType": "semver",
"lessThanOrEqual": "5.4.*"
},
{
"status": "unaffected",
"version": "5.10.235",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.179",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.130",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.83",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.14",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.13.3",
"versionType": "semver",
"lessThanOrEqual": "6.13.*"
},
{
"status": "unaffected",
"version": "6.14",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/sched/sch_fifo.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2025-21702
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #26912 · Revision 1
- Added to Heist Feed
- Publisher date