{"id":"CVE-2026-43288","title":"ext4: move ext4_percpu_param_init() before ext4_mb_init()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\next4: move ext4_percpu_param_init() before ext4_mb_init()\n\nWhen running `kvm-xfstests -c ext4/1k -C 1 generic/383` with the\n`DOUBLE_CHECK` macro defined, the following …","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < 0b3d80c56957862ba477ca0ce30c12cad9179c2b","Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < 0d5fcb063cdabb9aeaa8554b7fedad2092c4150e","Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < 9e9fb259bcddf459a0168f4a964e979e500a68a5","Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < bf5b609524497c195f801cd5707252384aed8149","Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < aec095f3cc6cf209effd93278ce35be27db81d73","Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < 270564513489d98b721a1e4a10017978d5213bff","Linux 3.17"],"published":"2026-05-08","updated":"2026-09-14","sourceUpdated":"2026-09-14T11:58:19.350Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-43288","references":[{"url":"https://git.kernel.org/stable/c/0b3d80c56957862ba477ca0ce30c12cad9179c2b"},{"url":"https://git.kernel.org/stable/c/0d5fcb063cdabb9aeaa8554b7fedad2092c4150e"},{"url":"https://git.kernel.org/stable/c/9e9fb259bcddf459a0168f4a964e979e500a68a5"},{"url":"https://git.kernel.org/stable/c/bf5b609524497c195f801cd5707252384aed8149"},{"url":"https://git.kernel.org/stable/c/aec095f3cc6cf209effd93278ce35be27db81d73"},{"url":"https://git.kernel.org/stable/c/270564513489d98b721a1e4a10017978d5213bff"}],"tags":["cve.org"],"epss":0.0013,"epssPercentile":0.03007,"ingestedAt":"2026-09-14T15:23:07.458Z","slug":"CVE-2026-43288","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\next4: move ext4_percpu_param_init() before ext4_mb_init()\n\nWhen running `kvm-xfstests -c ext4/1k -C 1 generic/383` with the\n`DOUBLE_CHECK` macro defined, the following panic is triggered:\n\n==================================================================\nEXT4-fs error (device vdc): ext4_validate_block_bitmap:423:\n                        comm mount: bg 0: bad block bitmap checksum\nBUG: unable to handle page fault for address: ff110000fa2cc000\nPGD 3e01067 P4D 3e02067 PUD 0\nOops: Oops: 0000 [#1] SMP NOPTI\nCPU: 0 UID: 0 PID: 2386 Comm: mount Tainted: G W\n                        6.18.0-gba65a4e7120a-dirty #1152 PREEMPT(none)\nRIP: 0010:percpu_counter_add_batch+0x13/0xa0\nCall Trace:\n <TASK>\n ext4_mark_group_bitmap_corrupted+0xcb/0xe0\n ext4_validate_block_bitmap+0x2a1/0x2f0\n ext4_read_block_bitmap+0x33/0x50\n mb_group_bb_bitmap_alloc+0x33/0x80\n ext4_mb_add_groupinfo+0x190/0x250\n ext4_mb_init_backend+0x87/0x290\n ext4_mb_init+0x456/0x640\n __ext4_fill_super+0x1072/0x1680\n ext4_fill_super+0xd3/0x280\n get_tree_bdev_flags+0x132/0x1d0\n vfs_get_tree+0x29/0xd0\n vfs_cmd_create+0x59/0xe0\n __do_sys_fsconfig+0x4f6/0x6b0\n do_syscall_64+0x50/0x1f0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n==================================================================\n\nThis issue can be reproduced using the following commands:\n        mkfs.ext4 -F -q -b 1024 /dev/sda 5G\n        tune2fs -O quota,project /dev/sda\n        mount /dev/sda /tmp/test\n\nWith DOUBLE_CHECK defined, mb_group_bb_bitmap_alloc() reads\nand validates the block bitmap. When the validation fails,\next4_mark_group_bitmap_corrupted() attempts to update\nsbi->s_freeclusters_counter. However, this percpu_counter has not been\ninitialized yet at this point, which leads to the panic described above.\n\nFix this by moving the execution of ext4_percpu_param_init() to occur\nbefore ext4_mb_init(), ensuring the per-CPU counters are initialized\nbefore they are used.\n\n## Affected\n\n- `Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < 0b3d80c56957862ba477ca0ce30c12cad9179c2b`\n- `Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < 0d5fcb063cdabb9aeaa8554b7fedad2092c4150e`\n- `Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < 9e9fb259bcddf459a0168f4a964e979e500a68a5`\n- `Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < bf5b609524497c195f801cd5707252384aed8149`\n- `Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < aec095f3cc6cf209effd93278ce35be27db81d73`\n- `Linux >= d5e03cbb0c88cd1be39f2adc37d602230045964b < 270564513489d98b721a1e4a10017978d5213bff`\n- `Linux 3.17`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}