{"id":"CVE-2025-37953","summary":"sch_htb: make htb_deactivate() idempotent","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nsch_htb: make htb_deactivate() idempotent\n\nAlan reported a NULL pointer dereference in htb_next_rb_node()\nafter we made htb_qlen_notify() idempotent.\n\nIt turns out in the following case it introduced some regression:\n\nhtb_dequeue_tree():\n  |-\u003e fq_codel_dequeue()\n    |-\u003e qdisc_tree_reduce_backlog()\n      |-\u003e htb_qlen_notify()\n        |-\u003e htb_deactivate()\n  |-\u003e htb_next_rb_node()\n  |-\u003e htb_deactivate()\n\nFor htb_next_rb_node(), after calling the 1st htb_deactivate(), the\nclprio[prio]-\u003eptr could be already set to  NULL, which means\nhtb_next_rb_node() is vulnerable here.\n\nFor htb_deactivate(), although we checked qlen before calling it, in\ncase of qlen==0 after qdisc_tree_reduce_backlog(), we may call it again\nwhich triggers the warning inside.\n\nTo fix the issues here, we need to:\n\n1) Make htb_deactivate() idempotent, that is, simply return if we\n   already call it before.\n2) Make htb_next_rb_node() safe against ptr==NULL.\n\nMany thanks to Alan for testing and for the reproducer.","modified":"2026-04-03T13:14:25.356248Z","published":"2025-05-20T16:01:47.818Z","related":["MGASA-2025-0182","MGASA-2025-0183","SUSE-SU-2025:01964-1","SUSE-SU-2025:01965-1","SUSE-SU-2025:01983-1","SUSE-SU-2025:02000-1","SUSE-SU-2025:02254-1","SUSE-SU-2025:02264-1","SUSE-SU-2025:02307-1","SUSE-SU-2025:02308-1","SUSE-SU-2025:02320-1","SUSE-SU-2025:02321-1","SUSE-SU-2025:02322-1","SUSE-SU-2025:02333-1","SUSE-SU-2025:02537-1","SUSE-SU-2025:02923-1","SUSE-SU-2025:20408-1","SUSE-SU-2025:20413-1","SUSE-SU-2025:20419-1","SUSE-SU-2025:20421-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/37xxx/CVE-2025-37953.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/31ff70ad39485698cf779f2078132d80b57f6c07"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3769478610135e82b262640252d90f6efb05be71"},{"type":"WEB","url":"https://git.kernel.org/stable/c/98cd7ed92753090a714f0802d4434314526fe61d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/99ff8a20fd61315bf9ae627440a5ff07d22ee153"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a9945f7cf1709adc5d2d31cb6cfc85627ce299a8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c2d25fddd867ce20a266806634eeeb5c30cb520c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c4792b9e38d2f61b07eac72f10909fa76130314b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c928dd4f6bf0c25c72b11824a1e9ac9bd37296a0"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/37xxx/CVE-2025-37953.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-37953"},{"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":"e6b45f4de763b00dc1c55e685e2dd1aaf525d3c1"},{"fixed":"99ff8a20fd61315bf9ae627440a5ff07d22ee153"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"32ae12ce6a9f6bace186ca7335220ff59b6cc3cd"},{"fixed":"a9945f7cf1709adc5d2d31cb6cfc85627ce299a8"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"967955c9e57f8eebfccc298037d4aaf3d42bc1c9"},{"fixed":"c2d25fddd867ce20a266806634eeeb5c30cb520c"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"73cf6af13153d62f9b76eff422eea79dbc70f15e"},{"fixed":"c928dd4f6bf0c25c72b11824a1e9ac9bd37296a0"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"bbbf5e0f87078b715e7a665d662a2c0e77f044ae"},{"fixed":"31ff70ad39485698cf779f2078132d80b57f6c07"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0a188c0e197383683fd093ab1ea6ce9a5869a6ea"},{"fixed":"98cd7ed92753090a714f0802d4434314526fe61d"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"a61f1b5921761fbaf166231418bc1db301e5bf59"},{"fixed":"c4792b9e38d2f61b07eac72f10909fa76130314b"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"5ba8b837b522d7051ef81bacf3d95383ff8edce5"},{"fixed":"3769478610135e82b262640252d90f6efb05be71"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-37953.json"}}],"schema_version":"1.7.5"}