{"id":"CVE-2026-64401","summary":"smb: client: resolve SWN tcon from live registrations","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: resolve SWN tcon from live registrations\n\ncifs_swn_notify() looks up a witness registration by id under\ncifs_swnreg_idr_mutex, drops the mutex, and then uses the registration's\ncached tcon pointer.  That pointer is not a lifetime reference, and it is\nnot a stable representative once cifs_get_swn_reg() lets multiple tcons\nfor the same net/share name share one registration id.\n\nA same-share second mount can keep the cifs_swn_reg alive after the first\ntcon unregisters and is freed.  The registration then still points at the\nfreed first tcon, so taking tc_lock or incrementing tc_count through\nswnreg-\u003etcon only moves the use-after-free earlier.  Taking tc_lock while\nholding cifs_swnreg_idr_mutex also violates the documented CIFS lock\norder.\n\nFix this by making the registration store only the stable witness\nidentity: id, net name, share name, and notify flags.  When a notify\narrives, copy that identity under cifs_swnreg_idr_mutex, drop the mutex,\nthen find and pin a live witness tcon that currently matches the net/share\npair under the normal cifs_tcp_ses_lock -\u003e tc_lock order.  The notification\npath uses that pinned tcon directly and drops the reference when done.\n\nRegistration and unregister messages now use the live tcon passed by the\ncaller instead of a cached tcon in the registration.  The final unregister\nsend is folded into cifs_swn_unregister() while the registration is still\nprotected by cifs_swnreg_idr_mutex.  This removes the previous\nfind/drop/reacquire raw-pointer window.  The release path only removes the\nidr entry and frees the stable identity strings.\n\nThis preserves the intended one-registration/many-tcon behavior: a\nregistration id represents a net/share pair, and notify handling acts on a\nlive representative selected at use time.  It also preserves CLIENT_MOVE\nordering for the representative tcon because the old-IP unregister is sent\nbefore cifs_swn_register() sends the new-IP register.","modified":"2026-08-18T03:30:52.795896846Z","published":"2026-07-25T08:50:44.361Z","related":["openSUSE-SU-2026:11476-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64401.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0700f946659d0ab2352ec8a9b1c6fc74b13a27d7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/51d18db392e5386a7bb9e816d611f14e600cca3c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/91b8a58c6ac15c7db6518f696389933282f88da7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/945b4a4a54497db1dcb2f20ef801a84e884dac21"},{"type":"WEB","url":"https://git.kernel.org/stable/c/aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ec457f9afe5ae9538bdcd58fd4cb442b9787e183"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64401.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64401"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"fed979a7e082bd9f25f9002c3c4f8740dacd0bc8"},{"fixed":"51d18db392e5386a7bb9e816d611f14e600cca3c"},{"fixed":"aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd"},{"fixed":"945b4a4a54497db1dcb2f20ef801a84e884dac21"},{"fixed":"91b8a58c6ac15c7db6518f696389933282f88da7"},{"fixed":"0700f946659d0ab2352ec8a9b1c6fc74b13a27d7"},{"fixed":"ec457f9afe5ae9538bdcd58fd4cb442b9787e183"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64401.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"6.1.178"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.145"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.97"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.39"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64401.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}