{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-72315", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-09T03:40:39.919Z", "datePublished": "2026-08-15T05:55:29.761Z", "dateUpdated": "2026-08-17T05:42:41.932Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:42:41.932Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: fix busy dentry warning on unmount after DIO\n\nCommit c68337442f03 (\"cifs: Fix busy dentry used after unmounting\") fixed\nthe issue in cifs where deferred close of a file led to a dentry reference\ncount not being released in umount, by flushing deferredclose_wq in\ncifs_kill_sb() to solve it.\n\nHowever, the cifs DIO path suffers from the same busy-dentry problem caused\nby a delayed dentry reference-count release:\n\n\t[dio]\t\t\t[cifsd]\t\t\t[close + umount]\nnetfs_unbuffered_write_iter_locked\n...\n\t\t\t\tcifs_demultiplex_thread\n netfs_unbuffered_write\n cifs_issue_write\n netfs_wait_for_in_progress_stream [1]\n\t\t\t\t...\n\t\t\t\t netfs_write_subrequest_terminated\n\t\t\t\t netfs_subreq_clear_in_progress\n\t\t\t\t netfs_wake_collector // wake [1]\n\t\t\t\t netfs_put_subrequest\n netfs_put_request\n queue_work(system_dfl_wq, xxx) [2]\n // dio write return\t\t\t\t\tcifs_close\n\t\t\t\t\t\t\t _cifsFileInfo_put\n\t\t\t\t\t\t\t // cfile->count 2->1\n\t\t\t\t\t\t\t --cfile->count [3]\n\n\t\t\t\t\t\t\t// umount\n\t\t\t\t\t\t\tcifs_kill_sb\n\t\t\t\t\t\t\t kill_anon_super\n\t\t\t\t\t\t\t // warning triggered!\n\t\t\t\t\t\t\t shrink_dcache_for_umount [4]\n[system_dfl_wq] [5]\nnetfs_free_request\n ...\n _cifsFileInfo_put\n // cfile->count 1->0\n --cfile->count\n queue_work(fileinfo_put_wq, xxx)\n\n[fileinfo_put_wq] [6]\ncifsFileInfo_put_work\n cifsFileInfo_put_final\n dput\n\nIf the umount path is triggered before [5], it results warning:\nBUG: Dentry 00000000eab1f070{i=9a917b66ae404fec,n=test} still in use (1)\n[unmount of cifs cifs]\n\nThe existing per-inode ictx->io_count wait in cifs_evict_inode() does not\nhelp: it lives in the inode eviction path, which runs after\nshrink_dcache_for_umount() has already warned about the busy dentries.\n\nFix it by adding a per-superblock outstanding-rreq counter that is\nincremented in cifs_init_request() and decremented in cifs_free_request().\nIn cifs_kill_sb(), before kill_anon_super(), wait for this counter to reach\n0 - which guarantees that all cleanup_work for this sb have run and thus\nall relevant cfile puts are queued on fileinfo_put_wq or serverclose_wq.\nThen drain the workqueue so the dentry refs are dropped.\n\nThis is a targeted wait, not a flush of the system-wide system_dfl_wq." } ], "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 flaw is reached through local VFS syscalls (open with O_DIRECT, pwrite, close, umount) on the in-kernel CIFS/SMB3 client mount teardown path, not via remote SMB packet handling or ksmbd server code.\nAC:L - The attacker controls both sides of the race by issuing concurrent O_DIRECT writes and close/umount from separate threads, can flood system_dfl_wq to widen the cleanup delay window, and can retry until the post-pwrite/pre-cleanup_work window is hit.\nPR:L - Exploitation requires only a local user with write access to files on an already-mounted CIFS/SMB3 share; mount/umount can be performed by the same attacker with namespace capabilities or triggered by autofs lazy-unmount on shared enterprise home-directory mounts.\nUI:N - No victim interaction is required; the attacker directly drives the open/pwrite/close/umount syscall sequence in a tight loop without relying on another user to open files or perform any action.\nS:U - Impact is confined to kernel heap corruption and privilege escalation within the same host; this is not a VM escape, sandbox escape, or cross-security-authority boundary flaw.\nC:H - Delayed netfs cleanup causes cifsFileInfo_put_final() to dereference dentry, inode, and cifsInodeInfo structures after superblock teardown has begun, constituting a use-after-free that can be leveraged for arbitrary kernel memory read.\nI:H - Post-unmount cifsFileInfo_put_final() performs lock operations and list manipulation on freed kernel objects via fileinfo_put_wq, enabling heap metadata corruption and control-flow hijacking for arbitrary write or code execution.\nA:H - The race triggers WARN in shrink_dcache_for_umount during umount, and subsequent use-after-free in the deferred dentry put worker can cause kernel oops, panic, or hang." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/client/cifs_fs_sb.h", "fs/smb/client/cifsfs.c", "fs/smb/client/connect.c", "fs/smb/client/file.c" ], "versions": [ { "version": "340cea84f691c5206561bb2e0147158fe02070be", "lessThan": "f0eac9c3c3711f24efc2aaf12b8ec3e54a38c214", "status": "affected", "versionType": "git" }, { "version": "340cea84f691c5206561bb2e0147158fe02070be", "lessThan": "75f5c412fa867efa0bf9b646bffe0d912109e84a", "status": "affected", "versionType": "git" }, { "version": "708c276f516d27beaded7f372ac8111cee43926c", "status": "affected", "versionType": "git" }, { "version": "0629a1a187e424373364d681b42b101894bdb548", "status": "affected", "versionType": "git" }, { "version": "0e4b8faaaebe3137bec5723ef2b3cb0437fb38fd", "status": "affected", "versionType": "git" }, { "version": "f655467a9973f964b267871e5fef533ad5014494", "status": "affected", "versionType": "git" }, { "version": "30afc6ea72cc6cf7c8d579e79b64232801c38d08", "status": "affected", "versionType": "git" }, { "version": "6.1.167", "lessThan": "6.2", "status": "affected", "versionType": "semver" }, { "version": "6.6.130", "lessThan": "6.7", "status": "affected", "versionType": "semver" }, { "version": "6.12.78", "lessThan": "6.13", "status": "affected", "versionType": "semver" }, { "version": "6.18.20", "lessThan": "6.19", "status": "affected", "versionType": "semver" }, { "version": "6.19.10", "lessThan": "6.20", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/client/cifs_fs_sb.h", "fs/smb/client/cifsfs.c", "fs/smb/client/connect.c", "fs/smb/client/file.c" ], "versions": [ { "version": "7.0", "status": "affected" }, { "version": "0", "lessThan": "7.0", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "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": "7.0", "versionEndExcluding": "7.1.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.2" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.167" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.130" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.78" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18.20" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19.10" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/f0eac9c3c3711f24efc2aaf12b8ec3e54a38c214" }, { "url": "https://git.kernel.org/stable/c/75f5c412fa867efa0bf9b646bffe0d912109e84a" } ], "title": "smb: client: fix busy dentry warning on unmount after DIO", "x_generator": { "engine": "bippy-1.2.0" } } } }