f2fs: fix to avoid racing on fsync_entry_slab by multi filesystem instances

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>

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index f26a1c34102a7c8bd009c7400418836b6744c7f9..c0bead0df66ad916fe09c9fee71104b092c1e0d5 100644 (file)
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -3620,6 +3620,8 @@ void f2fs_destroy_garbage_collection_cache(void);
  */
 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

diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
index 422146c6d866d9cc32c079e9e6108d89f4eac47e..4b2f7d1d5bf4ba38a02a8b797f17d6ab11e91b2e 100644 (file)
--- a/fs/f2fs/recovery.c
+++ b/fs/f2fs/recovery.c
@@ -788,13 +788,6 @@ int f2fs_recover_fsync_data(struct f2fs_sb_info *sbi, bool check_only)
        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);
+}

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 7d325bfaf65ae1c6033a5811edcbb7efad0ce86e..096492caaa6bfde4ab4ff814cd1adda57bd23040 100644 (file)
--- 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();