{"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":"2026-09-16T10:33:21.471Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-16T10:33:21.471Z"},"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-rc2","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-rc2"}]}]}],"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"}}}}