{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-80970","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-08-26T14:34:25.810Z","datePublished":"2026-09-11T19:42:33.789Z","dateUpdated":"2026-09-14T11:59:17.143Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-14T11:59:17.143Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: FCP: do not copy out an uninitialised init response\n\nfcp_ioctl_init() allocates its response buffer with kmalloc() and copies\nthe whole buffer back to userspace:\n\n\tbuf_size = init.step0_resp_size + init.step2_resp_size;\n\n\tvoid *resp __free(kfree) =\n\t\tkmalloc(buf_size, GFP_KERNEL);\n\t...\n\tif (copy_to_user(arg->resp, resp, buf_size))\n\t\treturn -EFAULT;\n\nNothing clears the buffer, and the only writer of its leading\nstep0_resp_size bytes is the step-0 control transfer:\n\n\terr = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0),\n\t\tFCP_USB_REQ_STEP0,\n\t\tUSB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,\n\t\t0, private->bInterfaceNumber,\n\t\tstep0_resp, private->step0_resp_size);\n\tif (err < 0)\n\t\treturn err;\n\nusb_fill_control_urb() does not set URB_SHORT_NOT_OK, so a short or\nzero-length data stage completes with status 0 and snd_usb_ctl_msg()\nreturns a small actual_length.  The only check is err < 0, so a short\ntransfer is accepted as success.\n\nsnd_usb_ctl_msg() copies the full size back unconditionally:\n\n\tbuf = kmemdup(data, size, GFP_KERNEL);\n\t...\n\tmemcpy(data, buf, size);\n\nBytes the device never wrote are therefore restored into resp unchanged\nand copied to userspace.  step0_resp_size and step2_resp_size are each\nvalidated only to 1..255, so the caller also picks the slab cache, from\nkmalloc-8 up to kmalloc-512.\n\nOn 7.2.0-rc5 (arm64), device answering step 0 with a zero-length data\nstage, s0 = s2 = 255:\n\n  # init_on_alloc off, no spray\n  step0 window [0,255): nonzero=94/255\n  000: 00 80 60 06 00 00 ff ff 18 00 00 00 57 01 ea 01\n  010: 08 78 22 13 00 00 ff ff a8 c4 5f 80 00 80 ff ff\n\n  # same kernel, kmalloc-512 pre-seeded with an 8-byte tag\n  step0 window [0,255): nonzero=219/255  tagbytes=232\n\n  # identical run, init_on_alloc=1\n  step0 window [0,255): nonzero=0/255  tagbytes=0\n\n  # all three runs\n  step2 window [255,510): device words matched=62/62\n\na8 c4 5f 80 00 80 ff ff is the little-endian kernel text address\nffff8000805fc4a8.  The step-2 window is unaffected, so the disclosure is\nexactly the step-0 region.\n\nZero the buffer, and require the step-0 transfer to deliver the full\nstep0_resp_size bytes so a short data stage is reported as an error.\n\nDiscovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>"}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["sound/usb/fcp.c"],"versions":[{"version":"46757a3e7d50dac923888e7fbe68377736f13c70","lessThan":"e9e52437120fb5f802152877ba20c4b406c9fa9e","status":"affected","versionType":"git"},{"version":"46757a3e7d50dac923888e7fbe68377736f13c70","lessThan":"29ab2df278ab4f1d238cd9c1c393ee00db175cba","status":"affected","versionType":"git"},{"version":"46757a3e7d50dac923888e7fbe68377736f13c70","lessThan":"4335e387786479889e6db691fe06d345e52ea536","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["sound/usb/fcp.c"],"versions":[{"version":"6.14","status":"affected"},{"version":"0","lessThan":"6.14","status":"unaffected","versionType":"semver"},{"version":"6.18.52","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.4","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3-rc1","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":"6.14","versionEndExcluding":"6.18.52"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.14","versionEndExcluding":"7.3-rc1"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/e9e52437120fb5f802152877ba20c4b406c9fa9e"},{"url":"https://git.kernel.org/stable/c/29ab2df278ab4f1d238cd9c1c393ee00db175cba"},{"url":"https://git.kernel.org/stable/c/4335e387786479889e6db691fe06d345e52ea536"}],"title":"ALSA: FCP: do not copy out an uninitialised init response","x_generator":{"engine":"bippy-1.2.0"}}}}