{"id":"CVE-2026-64359","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nnilfs2: reject CLEAN_SEGMENTS ioctl with out-of-range segment numbers\n\nSyzbot reported a hung task in nilfs_transaction_begin() where multiple\ntasks performing chmod() …","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnilfs2: reject CLEAN_SEGMENTS ioctl with out-of-range segment numbers\n\nSyzbot reported a hung task in nilfs_transaction_begin() where multiple\ntasks performing chmod() …","severity":"medium","cvss":5.5,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 2.6.31, < 5.10.261","linux_kernel >= 5.11, < 5.15.212","linux_kernel >= 5.16, < 6.1.178","linux_kernel >= 6.2, < 6.6.145","linux_kernel >= 6.7, < 6.12.96","linux_kernel >= 6.13, < 6.18.39","linux_kernel >= 6.19, < 7.1.4"],"patched":["linux_kernel 7.1.4"],"published":"2026-07-25","updated":"2026-09-04","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-64359","references":[{"url":"https://git.kernel.org/stable/c/0789f0a6710713254a08f3a7d2ecbb6d1cbcf0aa","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/0e7a690fe435f8d5ea3feb7c1d8d73ba7e8b8aa9","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/223463c488b0554212a94de971ea538eb2805fc7","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/286f77d002a337735c0846d7480a82d9cda2aa31","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/39607452b1400c7bf748f15122df4d058b768c5b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/3ed388ec3b8922383d1e2d4432d7bd4cbbf8364e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/876c98e0fc65f071680c03c2e2ee3ef7ff9ca078","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d26aef771b4f6923da9f89d6d5b70d8def5853de","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.00123,"epssPercentile":0.02349,"ingestedAt":"2026-09-05T13:39:56.841Z","slug":"CVE-2026-64359","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnilfs2: reject CLEAN_SEGMENTS ioctl with out-of-range segment numbers\n\nSyzbot reported a hung task in nilfs_transaction_begin() where multiple\ntasks performing chmod() on a nilfs2 mount blocked for over 143 seconds\nwaiting to acquire ns_segctor_sem for read:\n\n  INFO: task syz.0.17:5918 blocked for more than 143 seconds.\n  Call Trace:\n   schedule+0x164/0x360\n   rwsem_down_read_slowpath+0x6d9/0x940\n   down_read+0x99/0x2e0\n   nilfs_transaction_begin+0x364/0x710 fs/nilfs2/segment.c:221\n   nilfs_setattr+0x124/0x2c0 fs/nilfs2/inode.c:921\n   notify_change+0xc1a/0xf40\n   chmod_common+0x273/0x4a0\n   do_fchmodat+0x12d/0x230\n\nThe writer holding ns_segctor_sem was a concurrent\nNILFS_IOCTL_CLEAN_SEGMENTS caller, stuck inside printk while emitting\nper-element warnings from nilfs_sufile_updatev():\n\n   __nilfs_msg+0x373/0x450 fs/nilfs2/super.c:78\n   nilfs_sufile_updatev+0x21c/0x6d0 fs/nilfs2/sufile.c:186\n   nilfs_sufile_freev fs/nilfs2/sufile.h:93 [inline]\n   nilfs_free_segments fs/nilfs2/segment.c:1140 [inline]\n   nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1261 [inline]\n   nilfs_segctor_do_construct+0x1f55/0x76c0\n   nilfs_clean_segments+0x3bd/0xa50\n   nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:922 [inline]\n   nilfs_ioctl+0x261f/0x2780\n\nThe root cause is that user-supplied segment numbers are not validated\nbefore nilfs_clean_segments() begins doing work; the range check on\neach segnum is performed deep inside the call chain by\nnilfs_sufile_updatev(), which emits a nilfs_warn() per invalid entry\nwhile still holding the segctor lock and the sufile mi_sem.  Under load\n(repeated invocations across multiple mounts saturating the global\nprintk path), the cumulative printk latency keeps ns_segctor_sem held\nlong enough to trip the hung_task watchdog, blocking concurrent\noperations such as chmod() that need ns_segctor_sem for read.\n\nFix by validating the contents of kbufs[4] in nilfs_clean_segments()\nimmediately after acquiring ns_segctor_sem via nilfs_transaction_lock().\nHolding ns_segctor_sem serializes the check against\nnilfs_ioctl_resize(), which can modify ns_nsegments, so the validation\nuses a consistent value.  Out-of-range segment numbers are rejected\nwith -EINVAL before any segment-cleaning work begins, so the bad\nentries never reach the per-element diagnostic path inside\nnilfs_sufile_updatev().\n\n## Affected\n\n- `linux_kernel >= 2.6.31, < 5.10.261`\n- `linux_kernel >= 5.11, < 5.15.212`\n- `linux_kernel >= 5.16, < 6.1.178`\n- `linux_kernel >= 6.2, < 6.6.145`\n- `linux_kernel >= 6.7, < 6.12.96`\n- `linux_kernel >= 6.13, < 6.18.39`\n- `linux_kernel >= 6.19, < 7.1.4`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 7.1.4`","depth":"sunlit","depthScore":30,"depthScoreParts":{"impact":30.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}