{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2025-40220", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2025-40220", "idYear": 2025, "status": "PUBLISHED", "publishedAt": "2025-12-04T14:50:44.108Z", "updatedAt": "2026-05-23T16:01:42.651Z", "importedAt": "2026-10-24T01:57:34.152Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "fuse: fix livelock in synchronous file put from fuseblk workers", "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nfuse: fix livelock in synchronous file put from fuseblk workers\n\nI observed a hang when running generic/323 against a fuseblk server.\nThis test opens a file, initiates a lot of AIO writes to that file\ndescriptor, and closes the file descriptor before the writes complete.\nUnsurprisingly, the AIO exerciser threads are mostly stuck waiting for\nresponses from the fuseblk server:\n\n# cat /proc/372265/task/372313/stack\n[<0>] request_wait_answer+0x1fe/0x2a0 [fuse]\n[<0>] __fuse_simple_request+0xd3/0x2b0 [fuse]\n[<0>] fuse_do_getattr+0xfc/0x1f0 [fuse]\n[<0>] fuse_file_read_iter+0xbe/0x1c0 [fuse]\n[<0>] aio_read+0x130/0x1e0\n[<0>] io_submit_one+0x542/0x860\n[<0>] __x64_sys_io_submit+0x98/0x1a0\n[<0>] do_syscall_64+0x37/0xf0\n[<0>] entry_SYSCALL_64_after_hwframe+0x4b/0x53\n\nBut the /weird/ part is that the fuseblk server threads are waiting for\nresponses from itself:\n\n# cat /proc/372210/task/372232/stack\n[<0>] request_wait_answer+0x1fe/0x2a0 [fuse]\n[<0>] __fuse_simple_request+0xd3/0x2b0 [fuse]\n[<0>] fuse_file_put+0x9a/0xd0 [fuse]\n[<0>] fuse_release+0x36/0x50 [fuse]\n[<0>] __fput+0xec/0x2b0\n[<0>] task_work_run+0x55/0x90\n[<0>] syscall_exit_to_user_mode+0xe9/0x100\n[<0>] do_syscall_64+0x43/0xf0\n[<0>] entry_SYSCALL_64_after_hwframe+0x4b/0x53\n\nThe fuseblk server is fuse2fs so there's nothing all that exciting in\nthe server itself. So why is the fuse server calling fuse_file_put?\nThe commit message for the fstest sheds some light on that:\n\n\"By closing the file descriptor before calling io_destroy, you pretty\nmuch guarantee that the last put on the ioctx will be done in interrupt\ncontext (during I/O completion).\n\nAha. AIO fgets a new struct file from the fd when it queues the ioctx.\nThe completion of the FUSE_WRITE command from userspace causes the fuse\nserver to call the AIO completion function. The completion puts the\nstruct file, queuing a delayed fput to the fuse server task. When the\nfuse server task returns to userspace, it has to run the delayed fput,\nwhich in the case of a fuseblk server, it does synchronously.\n\nSending the FUSE_RELEASE command sychronously from fuse server threads\nis a bad idea because a client program can initiate enough simultaneous\nAIOs such that all the fuse server threads end up in delayed_fput, and\nnow there aren't any threads left to handle the queued fuse commands.\n\nFix this by only using asynchronous fputs when closing files, and leave\na comment explaining why.", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "5a18ec176c934ca1bc9dc61580a5e0e90a9b5733", "status": "affected", "versionType": "git", "lessThan": "548e1f2bac1d4df91a6138f26bb4ab00323fd948" }, { "version": "5a18ec176c934ca1bc9dc61580a5e0e90a9b5733", "status": "affected", "versionType": "git", "lessThan": "cfd1aa3e2b71f3327cb373c45a897c9028c62b35" }, { "version": "5a18ec176c934ca1bc9dc61580a5e0e90a9b5733", "status": "affected", "versionType": "git", "lessThan": "83b375c6efef69b1066ad2d79601221e7892745a" }, { "version": "5a18ec176c934ca1bc9dc61580a5e0e90a9b5733", "status": "affected", "versionType": "git", "lessThan": "bfd17b6138df0122a95989457d8e18ce0b86165e" }, { "version": "5a18ec176c934ca1bc9dc61580a5e0e90a9b5733", "status": "affected", "versionType": "git", "lessThan": "b26923512dbe57ae4917bafd31396d22a9d1691a" }, { "version": "5a18ec176c934ca1bc9dc61580a5e0e90a9b5733", "status": "affected", "versionType": "git", "lessThan": "f19a1390af448d9e193c08e28ea5f727bf3c3049" }, { "version": "5a18ec176c934ca1bc9dc61580a5e0e90a9b5733", "status": "affected", "versionType": "git", "lessThan": "26e5c67deb2e1f42a951f022fdf5b9f7eb747b01" }, { "version": "9efe56738fecd591b5bf366a325440f9b457ebd6", "status": "affected", "versionType": "git" }, { "version": "5c46eb076e0a1b2c1769287cd6942e4594ade1b1", "status": "affected", "versionType": "git" }, { "version": "83e6726210d6c815ce044437106c738eda5ff6f6", "status": "affected", "versionType": "git" }, { "version": "23d154c71721fd0fa6199851078f32e6bd765664", "status": "affected", "versionType": "git" }, { "version": "ca3edc920f5fd7d8ac040caaf109f925c24620a0", "status": "affected", "versionType": "git" }, { "version": "2.6.32.32", "status": "affected", "versionType": "semver", "lessThan": "2.6.33" }, { "version": "2.6.33.8", "status": "affected", "versionType": "semver", "lessThan": "2.6.34" }, { "version": "2.6.34.10", "status": "affected", "versionType": "semver", "lessThan": "2.6.35" }, { "version": "2.6.35.12", "status": "affected", "versionType": "semver", "lessThan": "2.6.36" }, { "version": "2.6.37.3", "status": "affected", "versionType": "semver", "lessThan": "2.6.38" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "2.6.38", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "2.6.38" }, { "version": "5.10.246", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.10.*" }, { "version": "5.15.196", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.15.*" }, { "version": "6.1.158", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.115", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.54", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.17.4", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.17.*" }, { "version": "6.18", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }