CVE-2026-43288

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ext4: move ext4_percpu_param_init() before ext4_mb_init()<br /> <br /> When running `kvm-xfstests -c ext4/1k -C 1 generic/383` with the<br /> `DOUBLE_CHECK` macro defined, the following panic is triggered:<br /> <br /> ==================================================================<br /> EXT4-fs error (device vdc): ext4_validate_block_bitmap:423:<br /> comm mount: bg 0: bad block bitmap checksum<br /> BUG: unable to handle page fault for address: ff110000fa2cc000<br /> PGD 3e01067 P4D 3e02067 PUD 0<br /> Oops: Oops: 0000 [#1] SMP NOPTI<br /> CPU: 0 UID: 0 PID: 2386 Comm: mount Tainted: G W<br /> 6.18.0-gba65a4e7120a-dirty #1152 PREEMPT(none)<br /> RIP: 0010:percpu_counter_add_batch+0x13/0xa0<br /> Call Trace:<br /> <br /> ext4_mark_group_bitmap_corrupted+0xcb/0xe0<br /> ext4_validate_block_bitmap+0x2a1/0x2f0<br /> ext4_read_block_bitmap+0x33/0x50<br /> mb_group_bb_bitmap_alloc+0x33/0x80<br /> ext4_mb_add_groupinfo+0x190/0x250<br /> ext4_mb_init_backend+0x87/0x290<br /> ext4_mb_init+0x456/0x640<br /> __ext4_fill_super+0x1072/0x1680<br /> ext4_fill_super+0xd3/0x280<br /> get_tree_bdev_flags+0x132/0x1d0<br /> vfs_get_tree+0x29/0xd0<br /> vfs_cmd_create+0x59/0xe0<br /> __do_sys_fsconfig+0x4f6/0x6b0<br /> do_syscall_64+0x50/0x1f0<br /> entry_SYSCALL_64_after_hwframe+0x76/0x7e<br /> ==================================================================<br /> <br /> This issue can be reproduced using the following commands:<br /> mkfs.ext4 -F -q -b 1024 /dev/sda 5G<br /> tune2fs -O quota,project /dev/sda<br /> mount /dev/sda /tmp/test<br /> <br /> With DOUBLE_CHECK defined, mb_group_bb_bitmap_alloc() reads<br /> and validates the block bitmap. When the validation fails,<br /> ext4_mark_group_bitmap_corrupted() attempts to update<br /> sbi-&gt;s_freeclusters_counter. However, this percpu_counter has not been<br /> initialized yet at this point, which leads to the panic described above.<br /> <br /> Fix this by moving the execution of ext4_percpu_param_init() to occur<br /> before ext4_mb_init(), ensuring the per-CPU counters are initialized<br /> before they are used.