GHSA-RPP5-W8V3-W64Q
Vulnerability from github – Published: 2026-09-17 18:31 – Updated: 2026-09-17 18:31In the Linux kernel, the following vulnerability has been resolved:
ptp: netc: fix period truncation and potential divide-by-zero in PEROUT
The max_period bound in net_timer_enable_perout() was computed as:
max_period = (u64)NETC_TMR_DEFAULT_FIPER + integral_period;
which exceeds U32_MAX when integral_period > 0 (e.g. 0x100000002 for the default 333333333 Hz clock). A period_ns that passes this check but exceeds U32_MAX is then silently truncated when stored into the u32 struct netc_pp::period field.
A truncated value of zero can reach netc_timer_set_perout_alarm(), where the local u32 period variable would also be 0, causing a divide-by-zero in roundup_u64(delta, period) whenever the stime < min_time branch is taken (which always happens for a start time of {0, 0}).
Additionally, netc_timer_enable_periodic_pulse() and netc_timer_enable_fiper() both compute:
fiper = pp->period - integral_period;
A zero pp->period results in an unsigned wraparound to 0xFFFFFFFD, mis-programming the FIPER hardware register.
Fix all three issues by capping max_period at NETC_TMR_DEFAULT_FIPER (0xFFFFFFFF). This ensures that any period_ns passing the range check fits in a u32 without truncation, so the stored value is always valid and non-zero. The accepted range is reduced by integral_period ns (typically only a few nanoseconds), which is negligible in practice.
{
"affected": [],
"aliases": [
"CVE-2026-90100"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-17T17:17:01Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nptp: netc: fix period truncation and potential divide-by-zero in PEROUT\n\nThe max_period bound in net_timer_enable_perout() was computed as:\n\n max_period = (u64)NETC_TMR_DEFAULT_FIPER + integral_period;\n\nwhich exceeds U32_MAX when integral_period \u003e 0 (e.g. 0x100000002 for\nthe default 333333333 Hz clock). A period_ns that passes this check but\nexceeds U32_MAX is then silently truncated when stored into the u32\nstruct netc_pp::period field.\n\nA truncated value of zero can reach netc_timer_set_perout_alarm(), where\nthe local u32 period variable would also be 0, causing a divide-by-zero\nin roundup_u64(delta, period) whenever the stime \u003c min_time branch is\ntaken (which always happens for a start time of {0, 0}).\n\nAdditionally, netc_timer_enable_periodic_pulse() and\nnetc_timer_enable_fiper() both compute:\n\n fiper = pp-\u003eperiod - integral_period;\n\nA zero pp-\u003eperiod results in an unsigned wraparound to 0xFFFFFFFD,\nmis-programming the FIPER hardware register.\n\nFix all three issues by capping max_period at NETC_TMR_DEFAULT_FIPER\n(0xFFFFFFFF). This ensures that any period_ns passing the range check\nfits in a u32 without truncation, so the stored value is always valid\nand non-zero. The accepted range is reduced by integral_period ns\n(typically only a few nanoseconds), which is negligible in practice.",
"id": "GHSA-rpp5-w8v3-w64q",
"modified": "2026-09-17T18:31:50Z",
"published": "2026-09-17T18:31:50Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-90100"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/08988d1941e180f0ad30d91233cb64f3418ba23c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/51fe3fe0ffec033bd831c71d9bee3dee827e491c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/777dbc9914b2f003f1d44af80c7a4a395c5961b2"
}
],
"schema_version": "1.4.0",
"severity": []
}
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