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ext4: protect superblock modifications with a buffer lock

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Protect all superblock modifications (including checksum computation)
with a superblock buffer lock. That way we are sure computed checksum
matches current superblock contents (a mismatch could cause checksum
failures in nojournal mode or if an unjournalled superblock update races
with a journalled one). Also we avoid modifying superblock contents
while it is being written out (which can cause DIF/DIX failures if we
are running in nojournal mode).

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20201216101844.22917-4-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Jan Kara
2020-12-16 11:18:39 +01:00
committed by Theodore Ts'o
parent 4392fbc4ba
commit 05c2c00f37
7 changed files with 28 additions and 2 deletions
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12
fs/ext4/resize.c
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@@ -899,7 +899,10 @@ static int add_new_gdb(handle_t *handle, struct inode *inode,
EXT4_SB(sb)->s_gdb_count++;
ext4_kvfree_array_rcu(o_group_desc);
lock_buffer(EXT4_SB(sb)->s_sbh);
le16_add_cpu(&es->s_reserved_gdt_blocks, -1);
ext4_superblock_csum_set(sb);
unlock_buffer(EXT4_SB(sb)->s_sbh);
err = ext4_handle_dirty_super(handle, sb);
if (err)
ext4_std_error(sb, err);
@@ -1384,6 +1387,7 @@ static void ext4_update_super(struct super_block *sb,
reserved_blocks *= blocks_count;
do_div(reserved_blocks, 100);
lock_buffer(sbi->s_sbh);
ext4_blocks_count_set(es, ext4_blocks_count(es) + blocks_count);
ext4_free_blocks_count_set(es, ext4_free_blocks_count(es) + free_blocks);
le32_add_cpu(&es->s_inodes_count, EXT4_INODES_PER_GROUP(sb) *
@@ -1421,6 +1425,8 @@ static void ext4_update_super(struct super_block *sb,
* active. */
ext4_r_blocks_count_set(es, ext4_r_blocks_count(es) +
reserved_blocks);
ext4_superblock_csum_set(sb);
unlock_buffer(sbi->s_sbh);
/* Update the free space counts */
percpu_counter_add(&sbi->s_freeclusters_counter,
@@ -1717,8 +1723,11 @@ static int ext4_group_extend_no_check(struct super_block *sb,
goto errout;
}
lock_buffer(EXT4_SB(sb)->s_sbh);
ext4_blocks_count_set(es, o_blocks_count + add);
ext4_free_blocks_count_set(es, ext4_free_blocks_count(es) + add);
ext4_superblock_csum_set(sb);
unlock_buffer(EXT4_SB(sb)->s_sbh);
ext4_debug("freeing blocks %llu through %llu\n", o_blocks_count,
o_blocks_count + add);
/* We add the blocks to the bitmap and set the group need init bit */
@@ -1874,10 +1883,13 @@ static int ext4_convert_meta_bg(struct super_block *sb, struct inode *inode)
if (err)
goto errout;
lock_buffer(sbi->s_sbh);
ext4_clear_feature_resize_inode(sb);
ext4_set_feature_meta_bg(sb);
sbi->s_es->s_first_meta_bg =
cpu_to_le32(num_desc_blocks(sb, sbi->s_groups_count));
ext4_superblock_csum_set(sb);
unlock_buffer(sbi->s_sbh);
err = ext4_handle_dirty_super(handle, sb);
if (err) {