{"id":"CVE-2026-93830","summary":"net: stmmac: xgmac2: disable RBUE in default RX interrupt mask","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: stmmac: xgmac2: disable RBUE in default RX interrupt mask\n\nEnabling the RX Buffer Unavailable (RBUE) interrupt is counterproductive\nand can trigger a MAC interrupt storm under heavy RX pressure. When the\nDMA runs out of RX descriptors it fires RBUE continuously until software\nrefills the ring.\n\nHowever, RBUE is redundant: the normal RX completion interrupt (RIE)\nalready triggers NAPI, which processes completed descriptors and refills\nthe ring, causing the DMA to resume. The RBUE handler itself only sets\nhandle_rx - the same outcome as RIE.\n\nOn Agilex5 under heavy RX pressure, the MAC interrupt (which includes\nRBUE) was observed firing 1,821,811,555 times against only 2,618,627\nactual RX completions - a ~695x ratio - confirming the severity of the\nstorm.\n\nRBUE does not provide OOM recovery. If page_pool is exhausted,\nstmmac_rx_refill() cannot advance the DMA tail pointer, the DMA stays\nsuspended, and RBUE fires again on the next NAPI completion - a storm\nwith no forward progress. This patch trades that storm for a clean\nstall with the same RX outcome. Proper OOM recovery is a pre-existing\ngap outside the scope of this fix.\n\nNote: as a consequence of disabling RBUE, the rx_buf_unav_irq ethtool\ncounter will always read 0 on XGMAC2 devices. This behaviour is already\ninconsistent across DWMAC core versions.\n\nRemove RBUE from XGMAC_DMA_INT_DEFAULT_EN and XGMAC_DMA_INT_DEFAULT_RX\nto prevent the interrupt storm while keeping normal RX handling intact.","modified":"2026-10-22T10:34:19.673862014Z","published":"2026-09-24T16:03:12.818Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/93xxx/CVE-2026-93830.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0b1a5d3647ce07c27a9fffefc11a8cbf7d7b25ce"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6b3b91433d5f4eae6865cdaa96f40cd67849e1f6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/74dbb85a6a254b5fc1f265a6cd61b2ba9d9221d7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7a10e54e42a8f73a8d731f5a281fc06bb41b9250"},{"type":"WEB","url":"https://git.kernel.org/stable/c/87e2826ed2058747ddf014c082569a46bfadd96b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8c9d57b5dc098b84631d0b3559c84c499ea2170a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d3265c19b35d036bba327b36b5366bee76b0157c"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/93xxx/CVE-2026-93830.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-93830"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"d6ddfacd95c79d43465d4a85dffb1c9beca343a9"},{"fixed":"8c9d57b5dc098b84631d0b3559c84c499ea2170a"},{"fixed":"7a10e54e42a8f73a8d731f5a281fc06bb41b9250"},{"fixed":"6b3b91433d5f4eae6865cdaa96f40cd67849e1f6"},{"fixed":"74dbb85a6a254b5fc1f265a6cd61b2ba9d9221d7"},{"fixed":"0b1a5d3647ce07c27a9fffefc11a8cbf7d7b25ce"},{"fixed":"87e2826ed2058747ddf014c082569a46bfadd96b"},{"fixed":"d3265c19b35d036bba327b36b5366bee76b0157c"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-93830.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.19.0"},{"fixed":"5.10.271"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.222"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.189"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.158"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.111"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.53"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-93830.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}