ext4: check to make make sure bd_dev is set before dereferencing it

There are some drivers which may not set bdev->bd_dev.  So make sure
it is non-NULL before dereferencing it.

Google-Bug-Id: 1773557

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c1036bc8a5396141d15337e005d9c48d0a4f769e..e046eba247820ee57bee3cb2590bdd28555aefde 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2304,6 +2304,8 @@ static ssize_t session_write_kbytes_show(struct ext4_attr *a,
 {
        struct super_block *sb = sbi->s_buddy_cache->i_sb;
 
+       if (!sb->s_bdev->bd_part)
+               return snprintf(buf, PAGE_SIZE, "0\n");
        return snprintf(buf, PAGE_SIZE, "%lu\n",
                        (part_stat_read(sb->s_bdev->bd_part, sectors[1]) -
                         sbi->s_sectors_written_start) >> 1);
@@ -2314,6 +2316,8 @@ static ssize_t lifetime_write_kbytes_show(struct ext4_attr *a,
 {
        struct super_block *sb = sbi->s_buddy_cache->i_sb;
 
+       if (!sb->s_bdev->bd_part)
+               return snprintf(buf, PAGE_SIZE, "0\n");
        return snprintf(buf, PAGE_SIZE, "%llu\n",
                        (unsigned long long)(sbi->s_kbytes_written +
                        ((part_stat_read(sb->s_bdev->bd_part, sectors[1]) -
@@ -2575,8 +2579,9 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
        sbi->s_resgid = EXT4_DEF_RESGID;
        sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS;
        sbi->s_sb_block = sb_block;
-       sbi->s_sectors_written_start = part_stat_read(sb->s_bdev->bd_part,
-                                                     sectors[1]);
+       if (sb->s_bdev->bd_part)
+               sbi->s_sectors_written_start =
+                       part_stat_read(sb->s_bdev->bd_part, sectors[1]);
 
        unlock_kernel();
 
@@ -3492,10 +3497,14 @@ static int ext4_commit_super(struct super_block *sb, int sync)
         */
        if (!(sb->s_flags & MS_RDONLY))
                es->s_wtime = cpu_to_le32(get_seconds());
-       es->s_kbytes_written =
-               cpu_to_le64(EXT4_SB(sb)->s_kbytes_written +
+       if (sb->s_bdev->bd_part)
+               es->s_kbytes_written =
+                       cpu_to_le64(EXT4_SB(sb)->s_kbytes_written +
                            ((part_stat_read(sb->s_bdev->bd_part, sectors[1]) -
                              EXT4_SB(sb)->s_sectors_written_start) >> 1));
+       else
+               es->s_kbytes_written =
+                       cpu_to_le64(EXT4_SB(sb)->s_kbytes_written);
        ext4_free_blocks_count_set(es, percpu_counter_sum_positive(
                                        &EXT4_SB(sb)->s_freeblocks_counter));
        es->s_free_inodes_count = cpu_to_le32(percpu_counter_sum_positive(