{"id":"CVE-2022-49755","state":"PUBLISHED","title":"usb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait\n\nWhile performing fast composition switch, there is a possibility that the\nprocess of ffs_ep0_write/ffs_ep0_read get into a race condition\ndue to ep0req being freed up from functionfs_unbind.\n\nConsider the scenario that the ffs_ep0_write calls the ffs_ep0_queue_wait\nby taking a lock &ffs->ev.waitq.lock. However, the functionfs_unbind isn't\nbounded so it can go ahead and mark the ep0req to NULL, and since there\nis no NULL check in ffs_ep0_queue_wait we will end up in use-after-free.\n\nFix this by making a serialized execution between the two functions using\na mutex_lock(ffs->mutex).","publishedAt":"2025-03-27T16:43:02.950Z","updatedAt":"2026-08-05T08:56:13.355Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"facf353c9e8d7885b686d9a4b173d4e0af6441d2","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"e9036e951f93fb8d7b5e9d6e2c7f94a4da312ae4","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"a8d40942df074f4ebcb9bd3413596d92f323b064","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"6dd9ea05534f323668db94fcc2726c7a84547e78","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"ae8e136bcaae96163b5821984de1036efc9abb1a","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"6aee197b7fbcd61596a78b47d553f2f99111f217","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"6a19da111057f69214b97c62fb0ac59023970850","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/usb/gadget/function/f_fs.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.35","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.35","versionType":"semver"},{"version":"4.14.305","status":"unaffected","lessThanOrEqual":"4.14.*","versionType":"semver"},{"version":"4.19.272","status":"unaffected","lessThanOrEqual":"4.19.*","versionType":"semver"},{"version":"5.4.231","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.166","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.91","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.9","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/usb/gadget/function/f_fs.c"]}],"references":["https://git.kernel.org/stable/c/facf353c9e8d7885b686d9a4b173d4e0af6441d2","https://git.kernel.org/stable/c/e9036e951f93fb8d7b5e9d6e2c7f94a4da312ae4","https://git.kernel.org/stable/c/a8d40942df074f4ebcb9bd3413596d92f323b064","https://git.kernel.org/stable/c/6dd9ea05534f323668db94fcc2726c7a84547e78","https://git.kernel.org/stable/c/ae8e136bcaae96163b5821984de1036efc9abb1a","https://git.kernel.org/stable/c/6aee197b7fbcd61596a78b47d553f2f99111f217","https://git.kernel.org/stable/c/6a19da111057f69214b97c62fb0ac59023970850"],"weaknesses":["CWE-416"],"ingestedAt":"2026-10-29T20:05:26.763Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2022/49xxx/CVE-2022-49755.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2022-49755","state":"PUBLISHED","datePublished":"2025-03-27T16:43:02.950Z","dateUpdated":"2026-08-05T08:56:13.355Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-03-27T16:39:17.988Z"},"containers":{"cna":{"title":"usb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_fs: Prevent race during ffs_ep0_queue_wait\n\nWhile performing fast composition switch, there is a possibility that the\nprocess of ffs_ep0_write/ffs_ep0_read get into a race condition\ndue to ep0req being freed up from functionfs_unbind.\n\nConsider the scenario that the ffs_ep0_write calls the ffs_ep0_queue_wait\nby taking a lock &ffs->ev.waitq.lock. However, the functionfs_unbind isn't\nbounded so it can go ahead and mark the ep0req to NULL, and since there\nis no NULL check in ffs_ep0_queue_wait we will end up in use-after-free.\n\nFix this by making a serialized execution between the two functions using\na mutex_lock(ffs->mutex)."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"facf353c9e8d7885b686d9a4b173d4e0af6441d2","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"e9036e951f93fb8d7b5e9d6e2c7f94a4da312ae4","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"a8d40942df074f4ebcb9bd3413596d92f323b064","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"6dd9ea05534f323668db94fcc2726c7a84547e78","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"ae8e136bcaae96163b5821984de1036efc9abb1a","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"6aee197b7fbcd61596a78b47d553f2f99111f217","versionType":"git"},{"version":"ddf8abd2599491cbad959c700b90ba72a5dce8d0","status":"affected","lessThan":"6a19da111057f69214b97c62fb0ac59023970850","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/usb/gadget/function/f_fs.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.35","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.35","versionType":"semver"},{"version":"4.14.305","status":"unaffected","lessThanOrEqual":"4.14.*","versionType":"semver"},{"version":"4.19.272","status":"unaffected","lessThanOrEqual":"4.19.*","versionType":"semver"},{"version":"5.4.231","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.166","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.91","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.9","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/usb/gadget/function/f_fs.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/facf353c9e8d7885b686d9a4b173d4e0af6441d2"},{"url":"https://git.kernel.org/stable/c/e9036e951f93fb8d7b5e9d6e2c7f94a4da312ae4"},{"url":"https://git.kernel.org/stable/c/a8d40942df074f4ebcb9bd3413596d92f323b064"},{"url":"https://git.kernel.org/stable/c/6dd9ea05534f323668db94fcc2726c7a84547e78"},{"url":"https://git.kernel.org/stable/c/ae8e136bcaae96163b5821984de1036efc9abb1a"},{"url":"https://git.kernel.org/stable/c/6aee197b7fbcd61596a78b47d553f2f99111f217"},{"url":"https://git.kernel.org/stable/c/6a19da111057f69214b97c62fb0ac59023970850"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The race is between local FunctionFS ep0 read/write syscalls and functionfs_unbind during composition switch/gadget teardown, not USB host packet parsing. This matches prior f_fs userspace-API UAF scoring (e.g. CVE-2024-36894, CVE-2025-71074) as Local rather than Physical.\nAC:L - The attacker drives both sides—ep0 I/O into __ffs_ep0_queue_wait and unbind via composition switch or FunctionFS close/unregister—and can retry the race freely. Per guidance, a race the attacker fully creates is AC:L.\nPR:L - FunctionFS mounts commonly use uid=/gid=/fmode= to delegate ep0 to unprivileged gadget daemons (adbd/shell on Android, embedded USB services). Once mounted by init, those accounts can open ep0 and participate in the race without init-namespace root.\nUI:N - The attacker performs ep0 operations and triggers unbind/composition teardown directly; no separate victim action is required beyond an already-deployed FunctionFS gadget.\nS:U - The use-after-free corrupts kernel heap within the same host kernel security authority. This is ordinary local privilege escalation, not a VM escape or IOMMU/sandbox boundary cross.\nC:H - functionfs_unbind frees the live usb_request (ep0req) while __ffs_ep0_queue_wait still uses it; reclaim of that heap object enables attacker-controlled contents and kernel memory disclosure via subsequent field/pointer use.\nI:H - The freed usb_request is written (buf/length/zero) and passed to usb_ep_queue/usb_ep_dequeue, so a reclaimed object yields arbitrary write and control-flow hijack primitives. Kernel UAFs are scored High for integrity.\nA:H - Dereferencing or queuing the freed ep0req (or the concurrently NULLed gadget pointer) causes kernel oops/panic; any such crash is High availability impact."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T08:56:13.355Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.35","versionEndExcluding":"4.14.305"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.35","versionEndExcluding":"4.19.272"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.35","versionEndExcluding":"5.4.231"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.35","versionEndExcluding":"5.10.166"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.35","versionEndExcluding":"5.15.91"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.35","versionEndExcluding":"6.1.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.35","versionEndExcluding":"6.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":7.8,"attackVector":"LOCAL","baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","integrityImpact":"HIGH","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"LOW","confidentialityImpact":"HIGH"}},{"other":{"type":"ssvc","content":{"id":"CVE-2022-49755","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2025-03-28T15:22:31.876200Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-416","lang":"en","type":"CWE","description":"CWE-416 Use After Free"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2025-03-28T15:31:59.379Z"}}]}}}