ext4: protect superblock modifications with a buffer lock

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>

diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
index 1a0a827..c7e410c 100644 (file)
--- a/fs/ext4/ext4_jbd2.c
+++ b/fs/ext4/ext4_jbd2.c
@@ -379,7 +379,6 @@ int __ext4_handle_dirty_super(const char *where, unsigned int line,
        struct buffer_head *bh = EXT4_SB(sb)->s_sbh;
        int err = 0;
 
-       ext4_superblock_csum_set(sb);
        if (ext4_handle_valid(handle)) {
                err = jbd2_journal_dirty_metadata(handle, bh);
                if (err)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 3ed8c04..26907d5 100644 (file)
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -809,8 +809,11 @@ static int ext4_sample_last_mounted(struct super_block *sb,
        err = ext4_journal_get_write_access(handle, sbi->s_sbh);
        if (err)
                goto out_journal;
+       lock_buffer(sbi->s_sbh);
        strlcpy(sbi->s_es->s_last_mounted, cp,
                sizeof(sbi->s_es->s_last_mounted));
+       ext4_superblock_csum_set(sb);
+       unlock_buffer(sbi->s_sbh);
        ext4_handle_dirty_super(handle, sb);
 out_journal:
        ext4_journal_stop(handle);

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 2794688..27de6f0 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5150,7 +5150,10 @@ static int ext4_do_update_inode(handle_t *handle,
                err = ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh);
                if (err)
                        goto out_brelse;
+               lock_buffer(EXT4_SB(sb)->s_sbh);
                ext4_set_feature_large_file(sb);
+               ext4_superblock_csum_set(sb);
+               unlock_buffer(EXT4_SB(sb)->s_sbh);
                ext4_handle_sync(handle);
                err = ext4_handle_dirty_super(handle, sb);
        }

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 7a890ff..40970a5 100644 (file)
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2978,7 +2978,10 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
            (le32_to_cpu(sbi->s_es->s_inodes_count))) {
                /* Insert this inode at the head of the on-disk orphan list */
                NEXT_ORPHAN(inode) = le32_to_cpu(sbi->s_es->s_last_orphan);
+               lock_buffer(sbi->s_sbh);
                sbi->s_es->s_last_orphan = cpu_to_le32(inode->i_ino);
+               ext4_superblock_csum_set(sb);
+               unlock_buffer(sbi->s_sbh);
                dirty = true;
        }
        list_add(&EXT4_I(inode)->i_orphan, &sbi->s_orphan);
@@ -3061,7 +3064,10 @@ int ext4_orphan_del(handle_t *handle, struct inode *inode)
                        mutex_unlock(&sbi->s_orphan_lock);
                        goto out_brelse;
                }
+               lock_buffer(sbi->s_sbh);
                sbi->s_es->s_last_orphan = cpu_to_le32(ino_next);
+               ext4_superblock_csum_set(inode->i_sb);
+               unlock_buffer(sbi->s_sbh);
                mutex_unlock(&sbi->s_orphan_lock);
                err = ext4_handle_dirty_super(handle, inode->i_sb);
        } else {

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 928700d..6155f2b 100644 (file)
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -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) {

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 8bf3100..2d653ad 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5444,6 +5444,7 @@ static int ext4_commit_super(struct super_block *sb)
        if (!sbh || block_device_ejected(sb))
                return error;
 
+       lock_buffer(sbh);
        /*
         * If the file system is mounted read-only, don't update the
         * superblock write time.  This avoids updating the superblock
@@ -5515,7 +5516,6 @@ static int ext4_commit_super(struct super_block *sb)
 
        BUFFER_TRACE(sbh, "marking dirty");
        ext4_superblock_csum_set(sb);
-       lock_buffer(sbh);
        if (buffer_write_io_error(sbh) || !buffer_uptodate(sbh)) {
                /*
                 * Oh, dear.  A previous attempt to write the

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 4e3b1f8..1db7ca7 100644 (file)
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -792,7 +792,10 @@ static void ext4_xattr_update_super_block(handle_t *handle,
 
        BUFFER_TRACE(EXT4_SB(sb)->s_sbh, "get_write_access");
        if (ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh) == 0) {
+               lock_buffer(EXT4_SB(sb)->s_sbh);
                ext4_set_feature_xattr(sb);
+               ext4_superblock_csum_set(sb);
+               unlock_buffer(EXT4_SB(sb)->s_sbh);
                ext4_handle_dirty_super(handle, sb);
        }
 }