CVE-2025-38218 Information

Jul 05, 2025 cve

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 $((512102410241024)) img mkfs.f2fs -f img $((25610241024)) resize.f2fs -s -i img -t $((102410241024)) 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 1928=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.

Reference

https://git.kernel.org/stable/c/38ef48a8afef8df646b6f6ae7abb872f18b533c1 https://git.kernel.org/stable/c/3e5ac62a56a24f4d88ce8ffd7bc452428b235868 https://git.kernel.org/stable/c/5db0d252c64e91ba1929c70112352e85dc5751e7 https://git.kernel.org/stable/c/79ef8a6c4ec53d327580fd7d2b522cf4f1d05b0c https://git.kernel.org/stable/c/82f51bff393e4c12cf4de553120ca831cfa4ef19 https://git.kernel.org/stable/c/ad862f71016ba38039df1c96ed55c0a4314cc183 https://git.kernel.org/stable/c/ee1b421c469876544e297ec1090574bd76100247

CNNVD-202507-471 (Published: 2025-07-04)

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