In the Linux kernel, the following vulnerability has been resolved:

f2fs: zone: fix to avoid inconsistence in between SIT and SSA

w/ below testcase, it will cause inconsistence in between SIT and SSA.

create_null_blk 512 2 1024 1024
mkfs.f2fs -m /dev/nullb0
mount /dev/nullb0 /mnt/f2fs/
touch /mnt/f2fs/file
f2fs_io pinfile set /mnt/f2fs/file
fallocate -l 4GiB /mnt/f2fs/file

F2FS-fs (nullb0): Inconsistent segment (0) type [1, 0] in SSA and SIT
CPU: 5 UID: 0 PID: 2398 Comm: fallocate Tainted: G           O       6.13.0-rc1 #84
Tainted: [O]=OOT_MODULE
Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
Call Trace:
 <TASK>
 dump_stack_lvl+0xb3/0xd0
 dump_stack+0x14/0x20
 f2fs_handle_critical_error+0x18c/0x220 [f2fs]
 f2fs_stop_checkpoint+0x38/0x50 [f2fs]
 do_garbage_collect+0x674/0x6e0 [f2fs]
 f2fs_gc_range+0x12b/0x230 [f2fs]
 f2fs_allocate_pinning_section+0x5c/0x150 [f2fs]
 f2fs_expand_inode_data+0x1cc/0x3c0 [f2fs]
 f2fs_fallocate+0x3c3/0x410 [f2fs]
 vfs_fallocate+0x15f/0x4b0
 __x64_sys_fallocate+0x4a/0x80
 x64_sys_call+0x15e8/0x1b80
 do_syscall_64+0x68/0x130
 entry_SYSCALL_64_after_hwframe+0x67/0x6f
RIP: 0033:0x7f9dba5197ca
F2FS-fs (nullb0): Stopped filesystem due to reason: 4

The reason is f2fs_gc_range() may try to migrate block in curseg, however,
its SSA block is not uptodate due to the last summary block data is still
in cache of curseg.

In this patch, we add a condition in f2fs_gc_range() to check whether
section is opened or not, and skip block migration for opened section.