{"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":"2026-10-03T10:55:48.520Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-10-03T10:55:48.520Z"},"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":"0e4b8faaaebe3137bec5723ef2b3cb0437fb38fd","lessThan":"f7748b551010c021d92f0125e37f32ac0c376d8a","status":"affected","versionType":"git"},{"version":"f655467a9973f964b267871e5fef533ad5014494","lessThan":"9fc87899276af941ecf3045798887db7deb85605","status":"affected","versionType":"git"},{"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":"30afc6ea72cc6cf7c8d579e79b64232801c38d08","status":"affected","versionType":"git"},{"version":"6.12.78","lessThan":"6.12.112","status":"affected","versionType":"semver"},{"version":"6.18.20","lessThan":"6.18.54","status":"affected","versionType":"semver"},{"version":"6.1.167","lessThan":"6.2","status":"affected","versionType":"semver"},{"version":"6.6.130","lessThan":"6.7","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":"6.12.112","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.54","lessThanOrEqual":"6.18.*","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":"6.12.78","versionEndExcluding":"6.12.112"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18.20","versionEndExcluding":"6.18.54"},{"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":"6.19.10"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/f7748b551010c021d92f0125e37f32ac0c376d8a"},{"url":"https://git.kernel.org/stable/c/9fc87899276af941ecf3045798887db7deb85605"},{"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"}}}}