{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-93121", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-17T16:02:15.086Z", "datePublished": "2026-09-17T16:11:27.220Z", "dateUpdated": "2026-10-19T09:05:54.766Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T09:05:54.766Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nusb: gadget: f_fs: Fix fence cleanup in ffs_dmabuf_transfer() error paths\n\nThe error paths for endpoint-disabled (ESHUTDOWN) and request-allocation\nfailure (ENOMEM) in ffs_dmabuf_transfer() jump to err_fence_put which\ncalls dma_fence_put() on the fence. However, at that point the fence has\nonly been kmalloc'd — dma_fence_init() has not been called yet, so the\nrefcount and the fence ops are uninitialized. Calling dma_fence_put() on\nsuch an object leads to undefined behavior.\n\nUse kfree() instead, since the fence is just a plain allocation at this\nstage, and rename the label to err_fence_free to reflect the actual\ncleanup action." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The uninitialized fence is kmalloc'd and then dma_fence_put() in ffs_dmabuf_transfer(), reached only from ffs_epfile_ioctl()'s FUNCTIONFS_DMABUF_TRANSFER case after copy_from_user of usb_ffs_dmabuf_transfer_req; USB host traffic never supplies that ioctl or the fence object.\nAC:H - err_fence_put runs only when epfile->ep != ep after ffs_epfile_wait_ep() (epfile->ep is NULLed solely by ffs_func_eps_disable() from gadget set_alt/disable/unbind) or when usb_ep_alloc_request(..., GFP_ATOMIC) fails; the ioctl caller cannot invoke those gadget callbacks and cannot reliably force that small GFP_ATOMIC allocation to fail.\nPR:L - ffs_epfile_ioctl() has no capable() check; FUNCTIONFS_DMABUF_TRANSFER only needs the endpoint file open. FunctionFS inodes take uid/gid/mode from ffs_fs_parse_param() (uid=/gid=/fmode=), which deployed gadgets use to hand ep nodes to non-root daemons such as adbd.\nUI:N - The attacker issues FUNCTIONFS_DMABUF_TRANSFER themselves on an endpoint fd they already hold; ffs_epfile_wait_ep() needing a prior host SET_CONFIGURATION is ambient gadget enumeration, not a victim action at exploit time.\nS:U - dma_fence_put() on the kmalloc'd ffs_dma_fence runs dma_fence_release() in the same kernel that hosts FunctionFS, so impact stays inside that kernel's privilege boundary rather than crossing a VM or IOMMU authority.\nC:H - kmalloc_obj(*fence) is not zeroed and dma_fence_init() has not run, so fence->refcount and fence->ops are leftover heap contents; dma_fence_put() calls dma_fence_release() if the sprayed refcount is 1, which rcu_dereference()s ops and reads other fence fields.\nI:H - dma_fence_release() calls ops->release() through the uninitialized fence->ops pointer (or walks garbage cb_list in the pending-signal path); a same-cache heap spray can point ops at attacker-controlled function pointers for control-flow hijack.\nA:H - dma_fence_release() does list_empty(&fence->cb_list) and dma_fence_lock_irqsave() on uninitialized cb_list/lock and may invoke a wild ops->release(), any of which oopses or panics when the ESHUTDOWN or ENOMEM err_fence_put path runs." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/usb/gadget/function/f_fs.c" ], "versions": [ { "version": "7b07a2a7ca02a20124b552be96c5a56910795488", "lessThan": "be539138d9a187af3b884525a395db10797c64f1", "status": "affected", "versionType": "git" }, { "version": "7b07a2a7ca02a20124b552be96c5a56910795488", "lessThan": "5fd8baacc7dc477df9cac61b45491840247a9b1e", "status": "affected", "versionType": "git" }, { "version": "7b07a2a7ca02a20124b552be96c5a56910795488", "lessThan": "58952c83dfe6ea3294a74734d2d1018c1120779a", "status": "affected", "versionType": "git" }, { "version": "7b07a2a7ca02a20124b552be96c5a56910795488", "lessThan": "621707dc67c9846fd876d7579ec951d92aa033f1", "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/gadget/function/f_fs.c" ], "versions": [ { "version": "6.9", "status": "affected" }, { "version": "0", "lessThan": "6.9", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.110", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.52", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.6", "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": "6.9", "versionEndExcluding": "6.12.110" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "6.18.52" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "7.2.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/be539138d9a187af3b884525a395db10797c64f1" }, { "url": "https://git.kernel.org/stable/c/5fd8baacc7dc477df9cac61b45491840247a9b1e" }, { "url": "https://git.kernel.org/stable/c/58952c83dfe6ea3294a74734d2d1018c1120779a" }, { "url": "https://git.kernel.org/stable/c/621707dc67c9846fd876d7579ec951d92aa033f1" } ], "title": "usb: gadget: f_fs: Fix fence cleanup in ffs_dmabuf_transfer() error paths", "x_generator": { "engine": "bippy-1.2.0" } } } }