{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-90015", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.781Z", "datePublished": "2026-09-16T10:33:21.471Z", "dateUpdated": "2026-10-19T08:56:28.983Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:56:28.983Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxhci: fix lost bounce buffers on TDs spanning several ring segments\n\nWhen a TD reaches a link TRB with data that is not aligned to the\nendpoint's wMaxPacketSize, xhci_align_td() stages the unalignable tail\nthrough the bounce buffer of the ring segment holding that link TRB.\nxhci_unmap_td_bounce_buffer() later unmaps it and, for IN transfers,\ncopies the data back into the URB's buffer.\n\nThe enqueue path records the segment that was bounced in td->bounce_seg,\nunder the assumption that a TD never spans more than two ring segments.\nThat assumption does not hold: a TD large enough to span three or more\nsegments crosses several link TRBs and can be bounced at each of them.\nOnly the last one survives in td->bounce_seg, so every earlier bounce\nbuffer is neither copied back nor DMA unmapped.\n\nThe URB still completes with actual_length equal to the requested length\nand no error, so the transfer looks successful while a wMaxPacketSize\nsized hole in the destination buffer silently keeps its previous\ncontents. It also leaks a DMA mapping per dropped bounce.\n\nAny sufficiently large and fragmented bulk transfer can hit this. It was\nfound with a USB mass storage device behind xHCI backing a dm-verity\ntarget with 512 byte hash blocks, where the stale data is detected rather\nthan silently consumed. The device enumerates as SuperSpeed, so\nwMaxPacketSize is 1024, while dm-bufio issues one 512 byte bio per hash\nblock. verity_prefetch_io() makes the block layer merge hundreds of them\ninto a single request of up to 512 scatterlist entries of 512 bytes each.\nAt 256 TRBs per ring segment such a TD spans three segments, and every\nsegment boundary falls on an odd multiple of 512, i.e. unaligned to\nwMaxPacketSize. dm-bufio then caches a hash block holding stale data and\ndm-verity declares the metadata block corrupted:\n\n device-mapper: verity: 8:2: metadata block 10850 is corrupted\n\nA reproducer running this under qemu is available at\nhttps://github.com/baloo/xhci-verity\n\nThe bounce state (bounce_buf, bounce_dma, bounce_len, bounce_offs)\nalready lives on the ring segment, so there is nothing extra to track.\nKeep recording the last bounced segment in td->bounce_seg and, on\ncompletion, walk the segments from td->start_seg up to it, unmapping\nevery segment that still has a pending bounce.\n\nStopping at td->bounce_seg rather than td->end_seg matters: a bounce\nimplies the TD continues past that segment's link TRB, so bounce_seg is\nalways strictly before end_seg, and a later TD may already have started\nin end_seg and been bounced there. Walking that far would copy a foreign\nbounce buffer into this URB and unmap it twice. It also keeps the walk\ncorrect if a TD ever wraps the whole ring so that end_seg == start_seg.\n\n[mn: Add ring->num_segs check to prevent unlikely infinite for loop.]" } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/usb/host/xhci-ring.c" ], "versions": [ { "version": "f9c589e142d04b8a19eb382162f804d17102b5ed", "lessThan": "c8124b28f12dbdd126118e63d0ebf8093a01fb81", "status": "affected", "versionType": "git" }, { "version": "f9c589e142d04b8a19eb382162f804d17102b5ed", "lessThan": "e04d5304a248e5d2a7f4faa87541644bdd320cfb", "status": "affected", "versionType": "git" }, { "version": "f9c589e142d04b8a19eb382162f804d17102b5ed", "lessThan": "a1629dfb011446d02905778f6df19f14c5f4f3b3", "status": "affected", "versionType": "git" }, { "version": "f9c589e142d04b8a19eb382162f804d17102b5ed", "lessThan": "43239fc6dfb62c50ae1b9c0e82bac0f8cd2e285c", "status": "affected", "versionType": "git" }, { "version": "f9c589e142d04b8a19eb382162f804d17102b5ed", "lessThan": "3c9a2b5a4f1183696f02ac280ced1d34afb409b1", "status": "affected", "versionType": "git" }, { "version": "f9c589e142d04b8a19eb382162f804d17102b5ed", "lessThan": "efaab8938fb92979be6df359f7d1a43fb7e4717d", "status": "affected", "versionType": "git" }, { "version": "f9c589e142d04b8a19eb382162f804d17102b5ed", "lessThan": "7236bbd2cb7d9fc0eda896bbd34790341e2a4377", "status": "affected", "versionType": "git" }, { "version": "f9c589e142d04b8a19eb382162f804d17102b5ed", "lessThan": "ff44dfb03a293bf30e31f98772a1dd316a6071d1", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/usb/host/xhci-ring.c" ], "versions": [ { "version": "4.8", "status": "affected" }, { "version": "0", "lessThan": "4.8", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.270", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.221", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.188", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.157", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.110", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.51", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.5", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "5.10.270" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "5.15.221" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.1.188" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.12.110" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "6.18.51" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "7.2.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/c8124b28f12dbdd126118e63d0ebf8093a01fb81" }, { "url": "https://git.kernel.org/stable/c/e04d5304a248e5d2a7f4faa87541644bdd320cfb" }, { "url": "https://git.kernel.org/stable/c/a1629dfb011446d02905778f6df19f14c5f4f3b3" }, { "url": "https://git.kernel.org/stable/c/43239fc6dfb62c50ae1b9c0e82bac0f8cd2e285c" }, { "url": "https://git.kernel.org/stable/c/3c9a2b5a4f1183696f02ac280ced1d34afb409b1" }, { "url": "https://git.kernel.org/stable/c/efaab8938fb92979be6df359f7d1a43fb7e4717d" }, { "url": "https://git.kernel.org/stable/c/7236bbd2cb7d9fc0eda896bbd34790341e2a4377" }, { "url": "https://git.kernel.org/stable/c/ff44dfb03a293bf30e31f98772a1dd316a6071d1" } ], "title": "xhci: fix lost bounce buffers on TDs spanning several ring segments", "x_generator": { "engine": "bippy-1.2.0" } } } }