{"id":"CVE-2026-80527","revision":"1295a00dec864cb49e041b8ec0fcca55","records":[{"revision":"1295a00dec864cb49e041b8ec0fcca55","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-80527","aliases":[],"title":"ceph: fix hanging __ceph_get_caps() with stale mds_wanted","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nceph: fix hanging __ceph_get_caps() with stale mds_wanted\n\nA reader can hang forever in __ceph_get_caps() when the client no\nlonger holds `FILE_RD`, but local cap state still says that the\ncapability is already wanted (via `mds_wanted`).\n\nOne way to trigger this is through MDS cap revocation. If another\nclient performs a conflicting operation, the MDS can revoke `FILE_RD`\nfrom the reader; the next read then has to reacquire `FILE_RD`. If\nthe cap update that should request `FILE_RD` never reaches the MDS\nafter `cap->mds_wanted` was raised, the reader is left holding only\nnon-file caps while local `mds_wanted` still includes the file read\ncaps.\n\nIn that state, try_get_cap_refs() sees `need <= mds_wanted` and\nreturns 0, so __ceph_get_caps() just waits on `i_cap_wq`. If the cap\nupdate that was supposed to request `FILE_RD never reaches the MDS\nafter `cap->mds_wanted was` raised, no further request is sent and the\nwaiter can sleep indefinitely until unrelated cap traffic happens to\nwake it up.\n\nThe ordering issue is that `cap->mds_wanted` is updated in\n__prep_cap() before the `CEPH_MSG_CLIENT_CAPS message` is actually\nqueued for send. That makes one field serve two different meanings at\nonce: what this client wants, and what the client believes the MDS\nalready knows it wants.\n\nA proper fix would be to split those states and track whether a cap\nupdate is actually in flight or has been observed by the MDS.\nHowever, simply moving the `cap->mds_wanted assignment` later would\nnot be sufficient: queueing the message in the messenger does not\nguarantee that the MDS processed that specific wanted set, and\nreconnect or message loss can still invalidate that assumption.\nFixing that properly would require a larger rework of the cap state\nmachine.\n\nTo allow simpler backports to stable kernels, this patch implements a\nsimpler workaround:\n\n- stop waiting forever in __ceph_get_caps(); after a bounded wait,\n fall back to the renew path\n\n- make ceph_renew_caps() issue a synchronous `OPEN` request whenever\n the inode still does not actually hold the wanted caps, instead of\n only calling ceph_check_caps()\n\nThe extra issued-vs-wanted check in ceph_renew_caps() is necessary\nbecause the previous test only checked whether the inode still had any\nreal caps at all. That is not enough after revocation: the client can\nstill hold something like `pLs` and yet be missing `FILE_RD`\ncompletely. In that case, falling back to ceph_check_caps() is not\nsufficient, because it still trusts `cap->mds_wanted` and may resend\nnothing. By requiring `(issued & wanted) == wanted` before taking the\nasynchronous path, the code only uses ceph_check_caps() when the\n`wanted caps` are already actually issued. Otherwise, it sends the\nsynchronous `OPEN` renew.\n\nThis preserves the existing asynchronous fast path when the wanted\ncaps are already issued, avoids changing cap-state semantics, and\nfixes the hang by guaranteeing that a stalled waiter eventually\nretries through a path that does not rely on the stale `mds_wanted`\nstate.\n\n[ idryomov: move CEPH_GET_CAPS_WAIT_TIMEOUT from libceph.h to\n mds_client.h, formatting ]","state":0,"publishedAt":"2026-08-26T14:37:06.178+00:00","modifiedAt":"2026-10-16T19:26:24.678+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/ceph/caps.c\",\n \"fs/ceph/file.c\",\n \"fs/ceph/mds_client.h\"\n ],\n \"versions\": [\n {\n \"version\": \"0a454bdd501ad1aa30bb72e9581efa338ad6ce5c\",\n \"lessThan\": \"b5661524c5a45085a866864ca9b8ae2513dfd67a\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"0a454bdd501ad1aa30bb72e9581efa338ad6ce5c\",\n \"lessThan\": \"5e84bc6f67e19fdd192d8b215de728acbfc12572\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"0a454bdd501ad1aa30bb72e9581efa338ad6ce5c\",\n \"lessThan\": \"5fedf279a1ea369d39c8b06dd4547cdc576065d0\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"0a454bdd501ad1aa30bb72e9581efa338ad6ce5c\",\n \"lessThan\": \"e05c315b4da0c16ea800ee4b2cb6c617f586d1b5\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"0a454bdd501ad1aa30bb72e9581efa338ad6ce5c\",\n \"lessThan\": \"fcce1b3be6d286aa80831e730289f4c062053ae6\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"0a454bdd501ad1aa30bb72e9581efa338ad6ce5c\",\n \"lessThan\": \"a3bc6b3e9ef3f5f5cb85a902a30a090c7931127c\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"0a454bdd501ad1aa30bb72e9581efa338ad6ce5c\",\n \"lessThan\": \"9e55fe24c548ad3163903eb58bb002d28d32a630\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"0a454bdd501ad1aa30bb72e9581efa338ad6ce5c\",\n \"lessThan\": \"50958bb928bad3bdba9e5d1b7ff4bbadcf6951e6\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/ceph/caps.c\",\n \"fs/ceph/file.c\",\n \"fs/ceph/mds_client.h\"\n ],\n \"versions\": [\n {\n \"version\": \"5.8\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"5.8\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.10.266\",\n \"lessThanOrEqual\": \"5.10.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.15.217\",\n \"lessThanOrEqual\": \"5.15.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.184\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.153\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.105\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.46\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.1.10\",\n \"lessThanOrEqual\": \"7.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.2\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/b5661524c5a45085a866864ca9b8ae2513dfd67a","https://git.kernel.org/stable/c/5e84bc6f67e19fdd192d8b215de728acbfc12572","https://git.kernel.org/stable/c/5fedf279a1ea369d39c8b06dd4547cdc576065d0","https://git.kernel.org/stable/c/e05c315b4da0c16ea800ee4b2cb6c617f586d1b5","https://git.kernel.org/stable/c/fcce1b3be6d286aa80831e730289f4c062053ae6","https://git.kernel.org/stable/c/a3bc6b3e9ef3f5f5cb85a902a30a090c7931127c","https://git.kernel.org/stable/c/9e55fe24c548ad3163903eb58bb002d28d32a630","https://git.kernel.org/stable/c/50958bb928bad3bdba9e5d1b7ff4bbadcf6951e6"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-80527","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-80527","identifiers":["CVE-2026-80527"]},"retained":false,"historicalAffected":[]}],"coverage":[]}