{"id":"CVE-2026-90015","revision":"011302c191dd4cfd8745999b01c6b89e","records":[{"revision":"011302c191dd4cfd8745999b01c6b89e","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-90015","aliases":[],"title":"xhci: fix lost bounce buffers on TDs spanning several ring segments","description":"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.]","state":0,"publishedAt":"2026-09-16T10:33:21.471+00:00","modifiedAt":"2026-10-19T08:56:28.983+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"drivers/usb/host/xhci-ring.c\"\n ],\n \"versions\": [\n {\n \"version\": \"f9c589e142d04b8a19eb382162f804d17102b5ed\",\n \"lessThan\": \"c8124b28f12dbdd126118e63d0ebf8093a01fb81\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f9c589e142d04b8a19eb382162f804d17102b5ed\",\n \"lessThan\": \"e04d5304a248e5d2a7f4faa87541644bdd320cfb\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f9c589e142d04b8a19eb382162f804d17102b5ed\",\n \"lessThan\": \"a1629dfb011446d02905778f6df19f14c5f4f3b3\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f9c589e142d04b8a19eb382162f804d17102b5ed\",\n \"lessThan\": \"43239fc6dfb62c50ae1b9c0e82bac0f8cd2e285c\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f9c589e142d04b8a19eb382162f804d17102b5ed\",\n \"lessThan\": \"3c9a2b5a4f1183696f02ac280ced1d34afb409b1\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f9c589e142d04b8a19eb382162f804d17102b5ed\",\n \"lessThan\": \"efaab8938fb92979be6df359f7d1a43fb7e4717d\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f9c589e142d04b8a19eb382162f804d17102b5ed\",\n \"lessThan\": \"7236bbd2cb7d9fc0eda896bbd34790341e2a4377\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f9c589e142d04b8a19eb382162f804d17102b5ed\",\n \"lessThan\": \"ff44dfb03a293bf30e31f98772a1dd316a6071d1\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"drivers/usb/host/xhci-ring.c\"\n ],\n \"versions\": [\n {\n \"version\": \"4.8\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"4.8\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.10.270\",\n \"lessThanOrEqual\": \"5.10.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.15.221\",\n \"lessThanOrEqual\": \"5.15.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.188\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.157\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.110\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.51\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.2.5\",\n \"lessThanOrEqual\": \"7.2.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.3\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/c8124b28f12dbdd126118e63d0ebf8093a01fb81","https://git.kernel.org/stable/c/e04d5304a248e5d2a7f4faa87541644bdd320cfb","https://git.kernel.org/stable/c/a1629dfb011446d02905778f6df19f14c5f4f3b3","https://git.kernel.org/stable/c/43239fc6dfb62c50ae1b9c0e82bac0f8cd2e285c","https://git.kernel.org/stable/c/3c9a2b5a4f1183696f02ac280ced1d34afb409b1","https://git.kernel.org/stable/c/efaab8938fb92979be6df359f7d1a43fb7e4717d","https://git.kernel.org/stable/c/7236bbd2cb7d9fc0eda896bbd34790341e2a4377","https://git.kernel.org/stable/c/ff44dfb03a293bf30e31f98772a1dd316a6071d1"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-90015","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-90015","identifiers":["CVE-2026-90015"]},"retained":false,"historicalAffected":[]}],"coverage":[]}