# CVE-2024-47691: linux: In the Linux kernel, the following vulnerability has been resolved:  f2fs: fix to avoid use-after-free in f2fs_stop_g...

CVE-2024-47691 is fixed in linux on 1 platform, first by DEBIAN-CVE-2024-47691, released October 21, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2024-47691
- Priority: High
- CVSS: 7.8 (high)
- EPSS: 0.0024
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 21, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  f2fs: fix to avoid use-after-free in f2fs_stop_gc_thread()  syzbot reports a f2fs bug as below:   __dump_stack lib/dump_stack.c:88 [inline]  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114  print_report+0xe8/0x550 mm/kasan/report.c:491  kasan_report+0x143/0x180 mm/kasan/report.c:601  kasan_check_range+0x282/0x290 mm/kasan/generic.c:189  instrument_atomic_read_write include/linux/instrumented.h:96 [inline]  atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:252 [inline]  __refcount_add include/linux/refcount.h:184 [inline]  __refcount_inc include/linux/refcount.h:241 [inline]  refcount_inc include/linux/refcount.h:258 [inline]  get_task_struct include/linux/sched/task.h:118 [inline]  kthread_stop+0xca/0x630 kernel/kthread.c:704  f2fs_stop_gc_thread+0x65/0xb0 fs/f2fs/gc.c:210  f2fs_do_shutdown+0x192/0x540 fs/f2fs/file.c:2283  f2fs_ioc_shutdown fs/f2fs/file.c:2325 [inline]  __f2fs_ioctl+0x443a/0xbe60 fs/f2fs/file.c:4325  vfs_ioctl fs/ioctl.c:51 [inline]  __do_sys_ioctl fs/ioctl.c:907 [inline]  __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893  do_syscall_x64 arch/x86/entry/common.c:52 [inline]  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83  entry_SYSCALL_64_after_hwframe+0x77/0x7f  The root cause is below race condition, it may cause use-after-free issue in sbi->gc_th pointer.  - remount  - f2fs_remount   - f2fs_stop_gc_thread    - kfree(gc_th) 				- f2fs_ioc_shutdown 				 - f2fs_do_shutdown 				  - f2fs_stop_gc_thread 				   - kthread_stop(gc_th->f2fs_gc_task)    : sbi->gc_thread = NULL;  We will call f2fs_do_shutdown() in two paths: - for f2fs_ioc_shutdown() path, we should grab sb->s_umount semaphore for fixing. - for f2fs_shutdown() path, it's safe since caller has already grabbed sb->s_umount semaphore.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.11.2-1 | [DEBIAN-CVE-2024-47691](https://patchblox.com/security/data/fix/linux/debian-cve-2024-47691.md) | Oct 21, 2024 |
| Linux | linux Debian 14 | 6.11.2-1 | [DEBIAN-CVE-2024-47691](https://patchblox.com/security/data/fix/linux/debian-cve-2024-47691.md) | Oct 21, 2024 |

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