CVE-2022-49738
Published: 27 March 2025
Summary
CVE-2022-49738 is a high-severity Out-of-bounds Read (CWE-125) vulnerability in Linux Linux Kernel. Its CVSS base score is 7.1 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Credential Access (T1212); ranked at the 11.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and SI-10 (Information Input Validation).
Deeper analysis
CVE-2022-49738 is a slab-out-of-bounds read vulnerability in the Linux kernel's f2fs filesystem implementation. The issue arises in the is_alive() function within the garbage collection code (gc_data_segment), where a missing sanity check on the i_extra_isize field leads to invalid memory access via offset_in_addr and data_blkaddr macros. This was detected by syzbot during kernel writeback operations on a tainted 6.1.0-rc4 kernel, resulting in a KASAN-reported read of 4 bytes at an invalid slab address.
A local attacker with low privileges (PR:L) can exploit this vulnerability with low attack complexity (AC:L) and no user interaction (UI:N) in a local attack vector (AV:L). Successful exploitation triggers the out-of-bounds read during f2fs garbage collection, potentially allowing high confidentiality impact through kernel memory disclosure (C:H) and high availability impact via system crash or denial of service (A:H), with no integrity impact (I:N). The CVSS v3.1 base score is 7.1, mapped to CWE-125 (Out-of-bounds Read).
Mitigation involves applying upstream patches from the provided stable kernel commit references, which add the necessary sanity check on i_extra_isize in the affected code path. Key commits include 5b25035fb888cb2f78bf0b9c9f95b1dc54480d36, 914e38f02a490dafd980ff0f39cccedc074deb29, 97ccfffcc061e54ce87e4a51a40e2e9cb0b7076a, d3b7b4afd6b2c344eabf9cc26b8bfa903c164c7c, and e5142a4935c1f15841d06047b8130078fc4d7b8f, backported to relevant stable branches.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2022-55185
Vulnerability details
In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to do sanity check on i_extra_isize in is_alive() syzbot found a f2fs bug: BUG: KASAN: slab-out-of-bounds in data_blkaddr fs/f2fs/f2fs.h:2891 [inline] BUG: KASAN: slab-out-of-bounds in is_alive fs/f2fs/gc.c:1117 [inline] BUG:…
more
KASAN: slab-out-of-bounds in gc_data_segment fs/f2fs/gc.c:1520 [inline] BUG: KASAN: slab-out-of-bounds in do_garbage_collect+0x386a/0x3df0 fs/f2fs/gc.c:1734 Read of size 4 at addr ffff888076557568 by task kworker/u4:3/52 CPU: 1 PID: 52 Comm: kworker/u4:3 Not tainted 6.1.0-rc4-syzkaller-00362-gfef7fd48922d #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 Workqueue: writeback wb_workfn (flush-7:0) Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_address_description mm/kasan/report.c:284 [inline] print_report+0x15e/0x45d mm/kasan/report.c:395 kasan_report+0xbb/0x1f0 mm/kasan/report.c:495 data_blkaddr fs/f2fs/f2fs.h:2891 [inline] is_alive fs/f2fs/gc.c:1117 [inline] gc_data_segment fs/f2fs/gc.c:1520 [inline] do_garbage_collect+0x386a/0x3df0 fs/f2fs/gc.c:1734 f2fs_gc+0x88c/0x20a0 fs/f2fs/gc.c:1831 f2fs_balance_fs+0x544/0x6b0 fs/f2fs/segment.c:410 f2fs_write_inode+0x57e/0xe20 fs/f2fs/inode.c:753 write_inode fs/fs-writeback.c:1440 [inline] __writeback_single_inode+0xcfc/0x1440 fs/fs-writeback.c:1652 writeback_sb_inodes+0x54d/0xf90 fs/fs-writeback.c:1870 wb_writeback+0x2c5/0xd70 fs/fs-writeback.c:2044 wb_do_writeback fs/fs-writeback.c:2187 [inline] wb_workfn+0x2dc/0x12f0 fs/fs-writeback.c:2227 process_one_work+0x9bf/0x1710 kernel/workqueue.c:2289 worker_thread+0x665/0x1080 kernel/workqueue.c:2436 kthread+0x2e4/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 The root cause is that we forgot to do sanity check on .i_extra_isize in below path, result in accessing invalid address later, fix it. - gc_data_segment - is_alive - data_blkaddr - offset_in_addr
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Kernel OOB read enables memory disclosure for credential access via exploitation (T1212); also facilitates system crash/DoS via application or system exploitation (T1499.004).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Flaw remediation directly mitigates CVE-2022-49738 by applying upstream kernel patches that add the missing sanity check on i_extra_isize in f2fs gc code, preventing the slab-out-of-bounds read.
Information input validation enforces checks on filesystem metadata like i_extra_isize before use in offset calculations, addressing the root cause of invalid memory access in is_alive().
Memory protection mechanisms such as kernel address space layout randomization and supervisor protections limit the impact of out-of-bounds reads by mitigating kernel memory disclosure and exploitation.