From: Chao Yu chao@kernel.org

mainline inclusion from mainline-v6.10-rc2 commit c7f114d864ac91515bb07ac271e9824a20f5ed95 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYPJO CVE: CVE-2024-47691

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

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[ Upstream commit c7f114d864ac91515bb07ac271e9824a20f5ed95 ]

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.

Reported-by: syzbot+1a8e2b31f2ac9bd3d148@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-f2fs-devel/0000000000005c7ccb061e032b9b@google... Fixes: 7950e9ac638e ("f2fs: stop gc/discard thread after fs shutdown") Signed-off-by: Chao Yu chao@kernel.org Signed-off-by: Jaegeuk Kim jaegeuk@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org Conflicts: fs/f2fs/file.c [Conflicts due to no code refactor in f2fs] Signed-off-by: Long Li leo.lilong@huawei.com --- fs/f2fs/file.c | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index eff0b359f1a3..4138e7e13845 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -2296,12 +2296,17 @@ static int f2fs_ioc_shutdown(struct file *filp, unsigned long arg) goto out; }

+ /* grab sb->s_umount to avoid racing w/ remount() */ + down_read(&sbi->sb->s_umount); + f2fs_stop_gc_thread(sbi); f2fs_stop_discard_thread(sbi);

f2fs_drop_discard_cmd(sbi); clear_opt(sbi, DISCARD);

+ up_read(&sbi->sb->s_umount); + f2fs_update_time(sbi, REQ_TIME); out: if (in != F2FS_GOING_DOWN_FULLSYNC)