CVE-2025-38218f2fs: fix to do sanity check on sit_bitmap_size

Official description

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to do sanity check on sit_bitmap_size w/ below testcase, resize will generate a corrupted image which contains inconsistent metadata, so when mounting such image, it will trigger kernel panic: touch img truncate -s $((512*1024*1024*1024)) img mkfs.f2fs -f img $((256*1024*1024)) resize.f2fs -s -i img -t $((1024*1024*1024)) mount img /mnt/f2fs ------------[ cut here ]------------ kernel BUG at fs/f2fs/segment.h:863! Oops: invalid opcode: 0000 [#1] SMP PTI CPU: 11 UID: 0 PID: 3922 Comm: mount Not tainted 6.15.0-rc1+ #191 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:f2fs_ra_meta_pages+0x47c/0x490 Call Trace: f2fs_build_segment_manager+0x11c3/0x2600 f2fs_fill_super+0xe97/0x2840 mount_bdev+0xf4/0x140 legacy_get_tree+0x2b/0x50 vfs_get_tree+0x29/0xd0 path_mount+0x487/0xaf0 __x64_sys_mount+0x116/0x150 do_syscall_64+0x82/0x190 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7fdbfde1bcfe The reaseon is: sit_i->bitmap_size is 192, so size of sit bitmap is 192*8=1536, at maximum there are 1536 sit blocks, however MAIN_SEGS is 261893, so that sit_blk_cnt is 4762, build_sit_entries() -> current_sit_addr() tries to access out-of-boundary in sit_bitmap at offset from [1536, 4762), once sit_bitmap and sit_bitmap_mirror is not the same, it will trigger f2fs_bug_on(). Let's add sanity check in f2fs_sanity_check_ckpt() to avoid panic.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/82f51bff393e4c12cf4de553120ca831cfa4ef19
• https://git.kernel.org/stable/c/38ef48a8afef8df646b6f6ae7abb872f18b533c1
• https://git.kernel.org/stable/c/ad862f71016ba38039df1c96ed55c0a4314cc183
• https://git.kernel.org/stable/c/79ef8a6c4ec53d327580fd7d2b522cf4f1d05b0c
• https://git.kernel.org/stable/c/ee1b421c469876544e297ec1090574bd76100247
• https://git.kernel.org/stable/c/3e5ac62a56a24f4d88ce8ffd7bc452428b235868
• https://git.kernel.org/stable/c/5db0d252c64e91ba1929c70112352e85dc5751e7
• https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html
• https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html