On 07/25, Chao Yu wrote: > 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) > > 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+1a8e2b31f2ac9bd3d...@syzkaller.appspotmail.com > Closes: > https://lore.kernel.org/linux-f2fs-devel/0000000000005c7ccb061e032...@google.com > Fixes: 7950e9ac638e ("f2fs: stop gc/discard thread after fs shutdown") > Signed-off-by: Chao Yu <c...@kernel.org> > --- > fs/f2fs/file.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index 7a37f2b393b9..62d72da25754 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -2388,7 +2388,10 @@ static int f2fs_ioc_shutdown(struct file *filp, > unsigned long arg) > } > } > > + /* grab sb->s_umount to avoid racing w/ remount() */ > + down_read(&sbi->sb->s_umount);
Is this safe for freeze_bdev()? > ret = f2fs_do_shutdown(sbi, in, readonly); > + up_read(&sbi->sb->s_umount); > > if (need_drop) > mnt_drop_write_file(filp); > -- > 2.40.1 _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
