[PATCH 5.13 266/266] f2fs: fix to avoid racing on fsync_entry_slab by multi filesystem instances

Greg Kroah-Hartman
2021-07-15T19:49:45Z

From: Chao Yu <yuchao0@huawei.com>

commit cad83c968c2ebe97905f900326988ed37146c347 upstream.

As syzbot reported, there is an use-after-free issue during f2fs recovery:

Use-after-free write at 0xffff88823bc16040 (in kfence-#10):
kmem_cache_destroy+0x1f/0x120 mm/slab_common.c:486
f2fs_recover_fsync_data+0x75b0/0x8380 fs/f2fs/recovery.c:869
f2fs_fill_super+0x9393/0xa420 fs/f2fs/super.c:3945
mount_bdev+0x26c/0x3a0 fs/super.c:1367
legacy_get_tree+0xea/0x180 fs/fs_context.c:592
vfs_get_tree+0x86/0x270 fs/super.c:1497
do_new_mount fs/namespace.c:2905 [inline]
path_mount+0x196f/0x2be0 fs/namespace.c:3235
do_mount fs/namespace.c:3248 [inline]
__do_sys_mount fs/namespace.c:3456 [inline]
__se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3433
do_syscall_64+0x3f/0xb0 arch/x86/entry/common.c:47
entry_SYSCALL_64_after_hwframe+0x44/0xae

The root cause is multi f2fs filesystem instances can race on accessing
global fsync_entry_slab pointer, result in use-after-free issue of slab
cache, fixes to init/destroy this slab cache only once during module
init/destroy procedure to avoid this issue.

Reported-by: syzbot+9d90dad32dd9727ed084@syzkaller.appspotmail.com
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/f2fs/f2fs.h | 2 ++
fs/f2fs/recovery.c | 23 ++++++++++++++---------
fs/f2fs/super.c | 8 +++++++-
3 files changed, 23 insertions(+), 10 deletions(-)

--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3566,6 +3566,8 @@ void f2fs_destroy_garbage_collection_cac
*/
int f2fs_recover_fsync_data(struct f2fs_sb_info *sbi, bool check_only);
bool f2fs_space_for_roll_forward(struct f2fs_sb_info *sbi);
+int __init f2fs_create_recovery_cache(void);
+void f2fs_destroy_recovery_cache(void);

/*
* debug.c
--- a/fs/f2fs/recovery.c
+++ b/fs/f2fs/recovery.c
@@ -788,13 +788,6 @@ int f2fs_recover_fsync_data(struct f2fs_
quota_enabled = f2fs_enable_quota_files(sbi, s_flags & SB_RDONLY);
#endif

- fsync_entry_slab = f2fs_kmem_cache_create("f2fs_fsync_inode_entry",
- sizeof(struct fsync_inode_entry));
- if (!fsync_entry_slab) {
- err = -ENOMEM;
- goto out;
- }
-
INIT_LIST_HEAD(&inode_list);
INIT_LIST_HEAD(&tmp_inode_list);
INIT_LIST_HEAD(&dir_list);
@@ -867,8 +860,6 @@ skip:
}
}

- kmem_cache_destroy(fsync_entry_slab);
-out:
#ifdef CONFIG_QUOTA
/* Turn quotas off */
if (quota_enabled)
@@ -878,3 +869,17 @@ out:

return ret ? ret : err;
}
+
+int __init f2fs_create_recovery_cache(void)
+{
+ fsync_entry_slab = f2fs_kmem_cache_create("f2fs_fsync_inode_entry",
+ sizeof(struct fsync_inode_entry));
+ if (!fsync_entry_slab)
+ return -ENOMEM;
+ return 0;
+}
+
+void f2fs_destroy_recovery_cache(void)
+{
+ kmem_cache_destroy(fsync_entry_slab);
+}
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -4227,9 +4227,12 @@ static int __init init_f2fs_fs(void)
err = f2fs_create_checkpoint_caches();
if (err)
goto free_segment_manager_caches;
- err = f2fs_create_extent_cache();
+ err = f2fs_create_recovery_cache();
if (err)
goto free_checkpoint_caches;
+ err = f2fs_create_extent_cache();
+ if (err)
+ goto free_recovery_cache;
err = f2fs_create_garbage_collection_cache();
if (err)
goto free_extent_cache;
@@ -4278,6 +4281,8 @@ free_garbage_collection_cache:
f2fs_destroy_garbage_collection_cache();
free_extent_cache:
f2fs_destroy_extent_cache();
+free_recovery_cache:
+ f2fs_destroy_recovery_cache();
free_checkpoint_caches:
f2fs_destroy_checkpoint_caches();
free_segment_manager_caches:
@@ -4303,6 +4308,7 @@ static void __exit exit_f2fs_fs(void)
f2fs_exit_sysfs();
f2fs_destroy_garbage_collection_cache();
f2fs_destroy_extent_cache();
+ f2fs_destroy_recovery_cache();
f2fs_destroy_checkpoint_caches();
f2fs_destroy_segment_manager_caches();
f2fs_destroy_node_manager_caches();