{"id":"CVE-2026-74599","summary":"mm/ptdump: always stabilise against page table freeing using init_mm","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/ptdump: always stabilise against page table freeing using init_mm\n\nPrevious commits have established the invariant that kernel page table\nfreeing is performed while an mmap read lock on init_mm is held, which\nfixes races between ptdump and kernel page table freeing over init_mm.\n\nHowever, x86 and arm64 can perform a ptdump over an mm other than init_mm\nvia ptdump_walk_pgd() and since kernel memory ranges are shared across\nnon-kernel mm's, this means that the race still exists for these cases.\n\nFix this by acquiring a nested mmap write lock for init_mm in\nptdump_walk_pgd().\n\nThis is safe as we take this after mmap write locking the mm, and nothing\nacquires the init_mm lock first before locking an arbitrary mm, so no\ndeadlock is possible.\n\nAlso update walk_page_range_debug() to assert that init_mm is write\nlocked, add a comment explaining why and remove some redundant code, and\neliminate the unnecessary and confusing invocation of\nwalk_kernel_page_table_range().\n\nWe can safely remove the non-NULL check for walk.mm, as the mmap lock\nasserts would NULL pointer deref if it was (and of course no callers do\nthis).\n\nThe first point at which ptdump can race kernel page table freeing is\ncommit b6bdb7517c3d (\"mm/vmalloc: add interfaces to free unmapped page\ntable\"), so we target this in the Fixes tag.","modified":"2026-11-01T02:30:59.877365297Z","published":"2026-08-22T15:31:48.604Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74599.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/27c32e5538344b13c1505a08861e04620c125d47"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3c0391b9a774cc0854f3152e484a9d4835b12b40"},{"type":"WEB","url":"https://git.kernel.org/stable/c/42c9464975cf21346a8950b8ba0ac3234b385be1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4adc4c9a9a43d61fe476dfe10811f3df2e7e4106"},{"type":"WEB","url":"https://git.kernel.org/stable/c/76df4edf7d61ecb711bc517ff4c20a5e85c4e9f7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7f740664aec1f832953c2e6d9b8920cd6c8bcc0c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b9c6d048bdfaae78d7d921b454f7de7baefaa2f0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cbd9583bb6f70733d0022a66d3546a15c76ae744"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74599.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74599"},{"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":"b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e"},{"fixed":"3c0391b9a774cc0854f3152e484a9d4835b12b40"},{"fixed":"cbd9583bb6f70733d0022a66d3546a15c76ae744"},{"fixed":"42c9464975cf21346a8950b8ba0ac3234b385be1"},{"fixed":"76df4edf7d61ecb711bc517ff4c20a5e85c4e9f7"},{"fixed":"b9c6d048bdfaae78d7d921b454f7de7baefaa2f0"},{"fixed":"7f740664aec1f832953c2e6d9b8920cd6c8bcc0c"},{"fixed":"4adc4c9a9a43d61fe476dfe10811f3df2e7e4106"},{"fixed":"27c32e5538344b13c1505a08861e04620c125d47"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.4.125"},{"fixed":"4.5"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.9.91"},{"fixed":"4.10"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.14.31"},{"fixed":"4.15"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4.15.14"},{"fixed":"4.16"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"31895cfd79564111cdd5a9f48c5d491ae26a238e"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"9c7f7bdb1932f8c1e5f80d32c717184701afe701"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"acdb4981644c8e31ccee294bdefff475c0cf587b"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0454e2fad9306961540ee7e84da47a8e345b7d22"}]}],"versions":["v4.4.302","v4.4.301","v4.4.300","v4.4.299","v4.4.298","v4.4.297","v4.4.296","v4.4.295","v4.4.294","v4.4.293","v4.4.292","v4.4.291","v4.4.290","v4.4.289","v4.4.288","v4.4.287","v4.4.286","v4.4.285","v4.4.284","v4.4.283","v4.4.282","v4.4.281","v4.4.280","v4.4.279","v4.4.278","v4.4.277","v4.4.276","v4.4.275","v4.4.274","v4.4.273","v4.4.272","v4.4.271","v4.4.270","v4.4.269","v4.4.268","v4.4.267","v4.4.266","v4.4.265","v4.4.264","v4.4.263","v4.4.262","v4.4.261","v4.4.260","v4.4.259","v4.4.258","v4.4.257","v4.4.256","v4.4.255","v4.4.254","v4.4.253","v4.4.252","v4.4.251","v4.4.250","v4.4.249","v4.4.248","v4.4.247","v4.4.246","v4.4.245","v4.4.244","v4.4.243","v4.4.242","v4.4.241","v4.4.240","v4.4.239","v4.4.238","v4.4.237","v4.4.236","v4.4.235","v4.4.234","v4.4.233","v4.4.232","v4.4.231","v4.4.230","v4.4.229","v4.4.228","v4.4.227","v4.4.226","v4.4.225","v4.4.224","v4.4.223","v4.4.222","v4.4.221","v4.4.220","v4.4.219","v4.4.218","v4.4.217","v4.4.216","v4.4.215","v4.4.214","v4.4.213","v4.4.212","v4.4.211","v4.4.210","v4.4.209","v4.4.208","v4.4.207","v4.4.206","v4.4.205","v4.4.204","v4.4.203","v4.4.202","v4.4.201","v4.4.200","v4.4.199","v4.4.198","v4.4.197","v4.4.196","v4.4.195","v4.4.194","v4.4.193","v4.4.192","v4.4.191","v4.4.190","v4.4.189","v4.4.188","v4.4.187","v4.4.186","v4.4.185","v4.4.184","v4.4.183","v4.4.182","v4.4.181","v4.4.180","v4.4.179","v4.4.178","v4.4.177","v4.4.176","v4.4.175","v4.4.174","v4.4.173","v4.4.172","v4.4.171","v4.4.170","v4.4.169","v4.4.168","v4.4.167","v4.4.166","v4.4.165","v4.4.164","v4.4.163","v4.4.162","v4.4.161","v4.4.160","v4.4.159","v4.4.158","v4.4.157","v4.4.156","v4.4.155","v4.4.154","v4.4.153","v4.4.152","v4.4.151","v4.4.150","v4.4.149","v4.4.148","v4.4.147","v4.4.146","v4.4.145","v4.4.144","v4.4.143","v4.4.142","v4.4.141","v4.4.140","v4.4.139","v4.4.138","v4.4.137","v4.4.136","v4.4.135","v4.4.134","v4.4.133","v4.4.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