ext4: init error handle resource before init group descriptors

Now, 's_err_report' timer is init after ext4_group_desc_init() when fill
super. Theoretically, ext4_group_desc_init() may access to error handle
as follows:
__ext4_fill_super
  ext4_group_desc_init
    ext4_check_descriptors
      ext4_get_group_desc
        ext4_error
          ext4_handle_error
            ext4_commit_super
              ext4_update_super
                if (!es->s_error_count)
                  mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ);
		  --> Accessing Uninitialized Variables
timer_setup(&sbi->s_err_report, print_daily_error_info, 0);

Maybe above issue is just theoretical, as ext4_check_descriptors() didn't
judge 'gpd' which get from ext4_get_group_desc(), if access to error handle
ext4_get_group_desc() will return NULL, then will trigger null-ptr-deref in
ext4_check_descriptors().
However, from the perspective of pure code, it is better to initialize
resource that may need to be used first.

Signed-off-by: Ye Bin <yebin10@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230119013711.86680-1-yebin@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 45bcfd35e5591715a9c1261074a0208545a19176..143e0b573ca58b1f75d4c894304baca75889c160 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4738,7 +4738,6 @@ static int ext4_group_desc_init(struct super_block *sb,
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        unsigned int db_count;
        ext4_fsblk_t block;
-       int ret;
        int i;
 
        db_count = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) /
@@ -4778,8 +4777,7 @@ static int ext4_group_desc_init(struct super_block *sb,
                        ext4_msg(sb, KERN_ERR,
                               "can't read group descriptor %d", i);
                        sbi->s_gdb_count = i;
-                       ret = PTR_ERR(bh);
-                       goto out;
+                       return PTR_ERR(bh);
                }
                rcu_read_lock();
                rcu_dereference(sbi->s_group_desc)[i] = bh;
@@ -4788,13 +4786,10 @@ static int ext4_group_desc_init(struct super_block *sb,
        sbi->s_gdb_count = db_count;
        if (!ext4_check_descriptors(sb, logical_sb_block, first_not_zeroed)) {
                ext4_msg(sb, KERN_ERR, "group descriptors corrupted!");
-               ret = -EFSCORRUPTED;
-               goto out;
+               return -EFSCORRUPTED;
        }
+
        return 0;
-out:
-       ext4_group_desc_free(sbi);
-       return ret;
 }
 
 static int ext4_load_and_init_journal(struct super_block *sb,
@@ -5220,14 +5215,14 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
        if (ext4_geometry_check(sb, es))
                goto failed_mount;
 
-       err = ext4_group_desc_init(sb, es, logical_sb_block, &first_not_zeroed);
-       if (err)
-               goto failed_mount;
-
        timer_setup(&sbi->s_err_report, print_daily_error_info, 0);
        spin_lock_init(&sbi->s_error_lock);
        INIT_WORK(&sbi->s_error_work, flush_stashed_error_work);
 
+       err = ext4_group_desc_init(sb, es, logical_sb_block, &first_not_zeroed);
+       if (err)
+               goto failed_mount3;
+
        /* Register extent status tree shrinker */
        if (ext4_es_register_shrinker(sbi))
                goto failed_mount3;