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

CVE-2025-38218 is fixed in linux on 1 platform, first by DEBIAN-CVE-2025-38218, released July 4, 2025. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2025-38218
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0019
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 4, 2025
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-38218

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 6.1.147-1 | [DEBIAN-CVE-2025-38218](https://patchblox.com/security/data/fix/linux/debian-cve-2025-38218.md) | Jul 4, 2025 |
| Linux | linux Debian 13.5 (trixie) | 6.12.35-1 | [DEBIAN-CVE-2025-38218](https://patchblox.com/security/data/fix/linux/debian-cve-2025-38218.md) | Jul 4, 2025 |
| Linux | linux Debian 14 | 6.12.35-1 | [DEBIAN-CVE-2025-38218](https://patchblox.com/security/data/fix/linux/debian-cve-2025-38218.md) | Jul 4, 2025 |

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