{"id":"CVE-2026-98538","state":"PUBLISHED","title":"writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nwriteback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes\n\ncleanup_offline_cgwb() prepares at most WB_MAX_INODES_PER_ISW inodes\nper call and is called again until the dying wb is drained, but every\ncall walks wb->b_attached and then wb->b_dirty_time from the same end.\nInodes already prepared (they stay on the list with I_WB_SWITCH set\nuntil the switch worker runs) and inodes that cannot be switched\n(I_FREEING, I_WILL_FREE, !SB_ACTIVE, DAX, already on the target wb)\nstay where they are, so each pass rescans a growing run of them under\nwb->list_lock and a full drain is quadratic in the number of inodes on\nthe list. With ~17M inodes attached to one dying cgwb we saw this end\nin soft lockups, with CPUs reported stuck for 21-48s.\n\nWalk both lists from the oldest end and move every scanned inode to\nthe newest end, so the next pass starts where the previous one stopped\nand the drain becomes linear. b_attached is unordered, so nobody sees\nthe reorder there. b_dirty_time is ordered by dirtied_when, but the\noldest unscanned inode stays at the end move_expired_inodes() picks\nfrom, sync takes the whole list regardless of order, and prepared\ninodes leave the list as soon as the switch work runs and get a new\ndirtied_time_when on the new wb anyway, so the only inodes left out of\norder are the ones that can never switch (DAX), and only on the dying\nwb.","publishedAt":"2026-10-18T15:18:05.901Z","updatedAt":"2026-10-19T09:21:21.678Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"2d1da58c79b66646721a644c6eb4dd1f9c5c9327","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"c96b4d1628868e1195da1a896f79e06f350a3187","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"624dd0931162523d70f9db8c120b5ec6429a9b97","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"dd4b92067238771b604b59fdda8efed6d70ee823","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"9dac137bf77e0683778fb34c86e730c6129e8cb6","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"f6988c90671e83db79df1b7b9d6fdb0e5947fd84","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/fs-writeback.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.14","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.112","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.55","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.9","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/fs-writeback.c"]}],"references":["https://git.kernel.org/stable/c/2d1da58c79b66646721a644c6eb4dd1f9c5c9327","https://git.kernel.org/stable/c/c96b4d1628868e1195da1a896f79e06f350a3187","https://git.kernel.org/stable/c/624dd0931162523d70f9db8c120b5ec6429a9b97","https://git.kernel.org/stable/c/dd4b92067238771b604b59fdda8efed6d70ee823","https://git.kernel.org/stable/c/9dac137bf77e0683778fb34c86e730c6129e8cb6","https://git.kernel.org/stable/c/f6988c90671e83db79df1b7b9d6fdb0e5947fd84"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98538.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98538","state":"PUBLISHED","datePublished":"2026-10-18T15:18:05.901Z","dateUpdated":"2026-10-19T09:21:21.678Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.356Z"},"containers":{"cna":{"title":"writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nwriteback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes\n\ncleanup_offline_cgwb() prepares at most WB_MAX_INODES_PER_ISW inodes\nper call and is called again until the dying wb is drained, but every\ncall walks wb->b_attached and then wb->b_dirty_time from the same end.\nInodes already prepared (they stay on the list with I_WB_SWITCH set\nuntil the switch worker runs) and inodes that cannot be switched\n(I_FREEING, I_WILL_FREE, !SB_ACTIVE, DAX, already on the target wb)\nstay where they are, so each pass rescans a growing run of them under\nwb->list_lock and a full drain is quadratic in the number of inodes on\nthe list. With ~17M inodes attached to one dying cgwb we saw this end\nin soft lockups, with CPUs reported stuck for 21-48s.\n\nWalk both lists from the oldest end and move every scanned inode to\nthe newest end, so the next pass starts where the previous one stopped\nand the drain becomes linear. b_attached is unordered, so nobody sees\nthe reorder there. b_dirty_time is ordered by dirtied_when, but the\noldest unscanned inode stays at the end move_expired_inodes() picks\nfrom, sync takes the whole list regardless of order, and prepared\ninodes leave the list as soon as the switch work runs and get a new\ndirtied_time_when on the new wb anyway, so the only inodes left out of\norder are the ones that can never switch (DAX), and only on the dying\nwb."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"2d1da58c79b66646721a644c6eb4dd1f9c5c9327","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"c96b4d1628868e1195da1a896f79e06f350a3187","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"624dd0931162523d70f9db8c120b5ec6429a9b97","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"dd4b92067238771b604b59fdda8efed6d70ee823","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"9dac137bf77e0683778fb34c86e730c6129e8cb6","versionType":"git"},{"version":"c22d70a162d3cc177282c4487be4d54876ca55c8","status":"affected","lessThan":"f6988c90671e83db79df1b7b9d6fdb0e5947fd84","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/fs-writeback.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.14","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.112","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.55","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.9","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/fs-writeback.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/2d1da58c79b66646721a644c6eb4dd1f9c5c9327"},{"url":"https://git.kernel.org/stable/c/c96b4d1628868e1195da1a896f79e06f350a3187"},{"url":"https://git.kernel.org/stable/c/624dd0931162523d70f9db8c120b5ec6429a9b97"},{"url":"https://git.kernel.org/stable/c/dd4b92067238771b604b59fdda8efed6d70ee823"},{"url":"https://git.kernel.org/stable/c/9dac137bf77e0683778fb34c86e730c6129e8cb6"},{"url":"https://git.kernel.org/stable/c/f6988c90671e83db79df1b7b9d6fdb0e5947fd84"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:21:21.678Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.1.189"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.6.158"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.12.112"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.18.55"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"7.2.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}