UBUNTU-CVE-2026-74269: Double Free
In the Linux kernel, the following vulnerability has been resolved: bnxt: fix head underflow on XDP head-grow The xdp.py test testxdpnativeadjstheadgrowdata crashes when run on a bnxt machine (and also crashes in NIPA). It seems that the bug is an underflow in bnxtrxmultipageskb, which builds the skb head: napibuildskb(dataptr - bp->rxoffset, rxr->rxpagesize); The problem with this expression is that in page mode, rxoffset is: bp->rxoffset = NETIPALIGN + XDPPACKETHEADROOM; Which evaluates (at least on x8664) to 258. The test testxdpnativeadjstheadgrowdata tests a case where the head is adjusted by -256. When this test runs, dataptr is shifted to fragstart + 2 (where fragstart = pageaddress(page) + offset). Then, bnxtrxmultipageskb is invoked and the napibuildskb expression subtracts 258, landing at an address before fragstart. This could be either the previous fragment or the previous physical page when the offset is < 256 (e.g. if the fragment started at offset 0). When the skb is freed, the page pool fragment reference is dropped on either the wrong page or the wrong frag of the right page. In either case, the corrupted reference count can lead to the page being prematurely recycled while still in use. Once (incorrectly) recycled, it can be handed out again and on driver teardown this would result in a double free. The commit under fixes updated this code to handle the case where the native page size is >= 64k, but it unintentionally broke the head grow case. To fix this, add an offset field to struct bnxtswrxbd, mirroring the existing offset field in struct bnxtswrxaggbd. Populate it on allocation and preserve it on reuse. In bnxtrxmultipageskb, use the newly added offset field to compute the fragment start and pass that to napibuildskb. Adjust the layout with skbreserve. There are two cases, the non-adjustment case and the adjustment case. In both cases, the skb is built at pageaddress(page) + offset to account for the case where the native page size >= 64K and skbreserve is called with dataptr - (pageaddress(page) + offset). That difference equals bp->rxoffset when dataptr was not moved, or bp->rxoffset + xdpadjust when XDP adjusted the head. Re-running the failing test with this commit applied causes the test to run successfully to completion. The other rxskbfunc implementations don't have this issue.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1013.13~24.04.1 - Upgrade
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ubuntu/linux-azure-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1017.17~24.04.1 - Upgrade
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ubuntu/linux-azure-fde-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1016.16~24.04.1 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1013.13~24.04.1 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-34.34~24.04.1 - Upgrade
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ubuntu/linux-nvidia-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1024.25~24.04.1 - Upgrade
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ubuntu/linux-nvidia-tegrato a version that resolves this vulnerability.Fixed in 6.8.0-1035.38 - Upgrade
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ubuntu/linux-oracle-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1012.12~24.04.1 - Upgrade
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ubuntu/linux-riscv-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-34.34.1~24.04.1 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-34.34 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1017.17 - Upgrade
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ubuntu/linux-azure-fdeto a version that resolves this vulnerability.Fixed in 7.0.0-1016.16 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1007.8 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-nvidia-bosto a version that resolves this vulnerability.Fixed in 7.0.0-2022.23 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 7.0.0-1012.12 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 7.0.0-1020.20 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-34.34.1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-34.34.1 - Compensating control
Fix the bnxt driver by adding an offset field to struct bnxt_sw_rx_bd, populating it on allocation and preserving it on reuse; in bnxt_rx_multi_page_skb, use the offset to compute frag_start and build the skb at page_address(page) + offset, passing the resulting fragment start to napi_build_skb so skb_reserve accounts for the offset and avoids corrupting the page-pool fragment reference count.
Event History
Frequently Asked Questions
Which Ubuntu kernel packages are identified as affected?
The listed packages are ubuntu/linux-riscv, ubuntu/linux-realtime, ubuntu/linux-azure, ubuntu/linux-gcp, ubuntu/linux-azure-fde, ubuntu/linux-gke, ubuntu/linux-hwe-edge, and ubuntu/linux-gkeop.
What level of access is required to exploit this issue?
The CVSS vector identifies local attack access and high privileges required. It does not require user interaction or additional attack-system privileges.
What conditions trigger the faulty path?
The issue occurs in the bnxt receive path when XDP head growth adjusts the data head backward, including the tested adjustment of -256. The resulting skb-head calculation can point before the fragment start and cause the wrong page-pool fragment reference to be released when the skb is freed.