{"id":"CVE-2026-63809","summary":"bpf: use kvfree() for replaced sysctl write buffer","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: use kvfree() for replaced sysctl write buffer\n\nproc_sys_call_handler() allocates its temporary sysctl buffer with\nkvzalloc() and passes it to __cgroup_bpf_run_filter_sysctl(). Since\nkvzalloc() may fall back to vmalloc() for large allocations, freeing\nthat buffer with kfree() is wrong and can corrupt memory.\n\nUse kvfree() to safely handle both kmalloc and kvzalloc()/vmalloc\nallocations.\n\nThe bug was first flagged by an experimental analysis tool we are\ndeveloping for kernel memory-management bugs while analyzing\nv6.13-rc1. The tool is still under development and is not yet publicly\navailable. Manual inspection confirms that the bug is still\npresent in v7.1-rc5.\n\nReproduced the bug based on v7.1-rc4 in a QEMU x86_64 guest booted with\nKASAN and CONFIG_FAILSLAB enabled. To exercise the replacement path, the\ntest tree also included the accompanying fix for the stale ret == 1\ncheck in __cgroup_bpf_run_filter_sysctl(). The reproducer confines\nfailslab injections to the proc_sys_call_handler() range, uses\nstacktrace-depth=32, and injects fail-nth=1 while writing 8191 bytes to\n/proc/sys/kernel/domainname from a task in the target cgroup. Under\nthat setup, fail-nth=1 triggered the fault:\n\n  BUG: unable to handle page fault for address: ffffeb0200024d48\n  #PF: supervisor read access in kernel mode\n  #PF: error_code(0x0000) - not-present page\n  PGD 0 P4D 0\n  Oops: Oops: 0000  SMP KASAN NOPTI\n  CPU: 2 UID: 0 PID: 209 Comm: repro_proc_sys_ Not tainted 7.1.0-rc4-00686-g97625979a5d4  PREEMPT(lazy)\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014\n  RIP: 0010:kfree+0x6e/0x510\n  ...\n  Call Trace:\n   \u003cTASK\u003e\n   ? __cgroup_bpf_run_filter_sysctl+0x626/0xc30\n   __cgroup_bpf_run_filter_sysctl+0x74d/0xc30\n   ? __pfx___cgroup_bpf_run_filter_sysctl+0x10/0x10\n   ? srso_return_thunk+0x5/0x5f\n   ? __kvmalloc_node_noprof+0x345/0x870\n   ? proc_sys_call_handler+0x250/0x480\n   ? srso_return_thunk+0x5/0x5f\n   proc_sys_call_handler+0x3a2/0x480\n   ? __pfx_proc_sys_call_handler+0x10/0x10\n   ? srso_return_thunk+0x5/0x5f\n   ? selinux_file_permission+0x39f/0x500\n   ? srso_return_thunk+0x5/0x5f\n   ? lock_is_held_type+0x9e/0x120\n   vfs_write+0x98e/0x1000\n   ...\n   \u003c/TASK\u003e\n\nWith this fix applied on top of the same test setup, rerunning the\nreproducer with fail-nth=1 yields no corresponding Oops reports.","modified":"2026-11-13T04:06:17.113882472Z","published":"2026-07-19T12:02:11.905Z","related":["SUSE-SU-2026:23066-1","SUSE-SU-2026:23068-1","SUSE-SU-2026:23193-1","SUSE-SU-2026:23194-1","SUSE-SU-2026:23221-1","SUSE-SU-2026:23231-1","SUSE-SU-2026:23237-1","SUSE-SU-2026:23241-1","SUSE-SU-2026:23244-1","SUSE-SU-2026:24550-1","SUSE-SU-2026:24619-1","SUSE-SU-2026:24643-1","SUSE-SU-2026:24648-1","SUSE-SU-2026:24651-1","SUSE-SU-2026:24662-1","SUSE-SU-2026:3790-1","SUSE-SU-2026:3810-1","SUSE-SU-2026:5091-1","openSUSE-SU-2026:11339-1","openSUSE-SU-2026:21555-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63809.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/4c21b5927d4364bfe7365f2700da5fea0ed0d004"},{"type":"WEB","url":"https://git.kernel.org/stable/c/65bd0c0afb0e1bf3287458e342429b069624f7d4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/70df4de46577fab5e25418f014583155a147c902"},{"type":"WEB","url":"https://git.kernel.org/stable/c/77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/81fc9a13acae99966232f0e055eb2e445263b89a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/838fe9c28121777c59a9406710a68fcf77bb8017"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63809.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-63809"},{"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":"b7925acd82926ebbf94a0f0783a3961f4e558856"},{"fixed":"d0a81ed5ff5d0f9c3f63a4f9e5a4642c363ecd3e"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4508943794efdd94171549c0bd52810e2f4ad9fe"},{"fixed":"77355ef7a9f6b0d2bdf65be3b37f2c1f365e20d2"},{"fixed":"e1d1e203a6000804c5d3b8a4aa4e52303c0c7ab2"},{"fixed":"81fc9a13acae99966232f0e055eb2e445263b89a"},{"fixed":"838fe9c28121777c59a9406710a68fcf77bb8017"},{"fixed":"65bd0c0afb0e1bf3287458e342429b069624f7d4"},{"fixed":"70df4de46577fab5e25418f014583155a147c902"},{"fixed":"4c21b5927d4364bfe7365f2700da5fea0ed0d004"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"66258ab303588936ee1ee0794d9a271be24f73cb"}]}],"versions":["v5.10.259","v5.10.258","v5.10.257","v5.10.256","v5.10.255","v5.10.254","v5.10.253","v5.10.252","v5.10.251","v5.10.250","v5.10.249","v5.10.248","v5.10.247","v5.10.246","v5.10.245","v5.10.244","v5.10.243","v5.10.242","v5.10.241","v5.10.240","v5.10.239","v5.10.238","v5.10.237","v5.10.236","v5.10.235","v5.10.234","v5.10.233","v5.10.232","v5.10.231","v5.10.230","v5.10.229","v5.10.228","v5.10.227","v5.10.226","v5.10.225","v5.10.224","v5.10.223","v5.10.222","v5.10.221","v5.10.220","v5.10.219","v5.10.218","v5.10.217","v5.10.216","v5.10.215","v5.10.214","v5.10.213","v5.10.212","v5.10.211","v5.10.210","v5.10.209","v5.10.208","v5.10.207","v5.10.206","v5.10.205","v5.10.204","v5.10.203","v5.10.202","v5.10.201","v5.10.200","v5.10.199","v5.10.198","v5.10.197","v5.10.196","v5.10.195","v5.10.194","v5.10.193","v5.10.192","v5.10.191","v5.10.190","v5.10.189","v5.10.188","v5.10.187","v5.10.186","v5.10.185","v5.10.184","v5.10.183","v5.10.182","v5.10.181","v5.10.180","v5.10.179","v5.10.178","v5.10.177","v5.10.176","v5.10.175","v5.10.174","v5.10.173","v5.10.172","v5.10.171","v5.10.170","v5.10.169","v5.10.168","v5.10.167","v5.10.166","v5.10.165","v5.10.164","v5.10.163","v5.10.162","v5.10.161","v5.10.160","v5.10.159","v5.10.158","v5.10.157","v5.10.156","v5.10.155","v5.10.154","v5.10.153","v5.10.152","v5.10.151","v5.10.150","v5.10.149","v5.10.148","v5.10.147","v5.10.146","v5.10.145","v5.10.144","v5.10.143","v5.10.142","v5.10.141","v5.10.140","v5.10.139","v5.10.138","v5.10.137","v5.10.136","v5.10.135","v5.10.134","v5.10.133","v5.10.132","v5.10.131","v5.10.130","v5.10.129","v5.10.128","v5.10.127","v5.10.126","v5.10.125","v5.10.124","v5.10.123","v5.10.122","v5.10.121","v5.10.120","v5.10.119","v5.10.118","v5.10.117","v5.10.116","v5.10.115","v5.10.114","v5.10.113","v5.10.112","v5.10.111","v5.10.110","v5.10.109","v5.10.108","v5.10.107","v5.10.106","v5.10.105","v5.10.104","v5.10.103","v5.10.102","v5.10.101","v5.10.100","v5.10.99","v5.10.98","v5.10.97","v5.10.96","v5.10.95","v5.10.94","v5.10.93","v5.10.92","v5.10.91","v5.10.90","v5.10.89","v5.10.88","v5.10.87","v5.10.86","v5.10.85","v5.10.84","v5.10.83","v5.10.82","v5.10.81","v5.10.80","v5.10.79","v5.10.78","v5.10.77","v5.10.76","v5.10.75","v5.10.74","v5.10.73","v5.10.72","v5.10.71","v5.10.70","v5.10.69","v5.10.68","v5.1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