ext4: prevent getting empty inode buffer

In ext4_get_inode_loc(), we may skip IO and get an zero && uptodate
inode buffer when the inode monopolize an inode block for performance
reason. For most cases, ext4_mark_iloc_dirty() will fill the inode
buffer to make it fine, but we could miss this call if something bad
happened. Finally, __ext4_get_inode_loc_noinmem() may probably get an
empty inode buffer and trigger ext4 error.

For example, if we remove a nonexistent xattr on inode A,
ext4_xattr_set_handle() will return ENODATA before invoking
ext4_mark_iloc_dirty(), it will left an uptodate but zero buffer. We
will get checksum error message in ext4_iget() when getting inode again.

  EXT4-fs error (device sda): ext4_lookup:1784: inode #131074: comm cat: iget: checksum invalid

Even worse, if we allocate another inode B at the same inode block, it
will corrupt the inode A on disk when write back inode B.

So this patch initialize the inode buffer by filling the in-mem inode
contents if we skip read I/O, ensure that the buffer is really uptodate.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20210901020955.1657340-4-yi.zhang@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index a46d5e022175f1921cbdc2232de7316e9bc1e637..bfd3545f1e5d933b76f3d7b182f849d9cea76511 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4380,12 +4380,12 @@ static int ext4_fill_raw_inode(struct inode *inode, struct ext4_inode *raw_inode
 
 /*
  * ext4_get_inode_loc returns with an extra refcount against the inode's
- * underlying buffer_head on success. If 'in_mem' is true, we have all
- * data in memory that is needed to recreate the on-disk version of this
- * inode.
+ * underlying buffer_head on success. If we pass 'inode' and it does not
+ * have in-inode xattr, we have all inode data in memory that is needed
+ * to recreate the on-disk version of this inode.
  */
 static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino,
-                               struct ext4_iloc *iloc, int in_mem,
+                               struct inode *inode, struct ext4_iloc *iloc,
                                ext4_fsblk_t *ret_block)
 {
        struct ext4_group_desc  *gdp;
@@ -4431,7 +4431,7 @@ static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino,
         * is the only valid inode in the block, we need not read the
         * block.
         */
-       if (in_mem) {
+       if (inode && !ext4_test_inode_state(inode, EXT4_STATE_XATTR)) {
                struct buffer_head *bitmap_bh;
                int i, start;
 
@@ -4459,8 +4459,13 @@ static int __ext4_get_inode_loc(struct super_block *sb, unsigned long ino,
                }
                brelse(bitmap_bh);
                if (i == start + inodes_per_block) {
+                       struct ext4_inode *raw_inode =
+                               (struct ext4_inode *) (bh->b_data + iloc->offset);
+
                        /* all other inodes are free, so skip I/O */
                        memset(bh->b_data, 0, bh->b_size);
+                       if (!ext4_test_inode_state(inode, EXT4_STATE_NEW))
+                               ext4_fill_raw_inode(inode, raw_inode);
                        set_buffer_uptodate(bh);
                        unlock_buffer(bh);
                        goto has_buffer;
@@ -4521,7 +4526,7 @@ static int __ext4_get_inode_loc_noinmem(struct inode *inode,
        ext4_fsblk_t err_blk;
        int ret;
 
-       ret = __ext4_get_inode_loc(inode->i_sb, inode->i_ino, iloc, 0,
+       ret = __ext4_get_inode_loc(inode->i_sb, inode->i_ino, NULL, iloc,
                                        &err_blk);
 
        if (ret == -EIO)
@@ -4536,9 +4541,8 @@ int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc)
        ext4_fsblk_t err_blk;
        int ret;
 
-       /* We have all inode data except xattrs in memory here. */
-       ret = __ext4_get_inode_loc(inode->i_sb, inode->i_ino, iloc,
-               !ext4_test_inode_state(inode, EXT4_STATE_XATTR), &err_blk);
+       ret = __ext4_get_inode_loc(inode->i_sb, inode->i_ino, inode, iloc,
+                                       &err_blk);
 
        if (ret == -EIO)
                ext4_error_inode_block(inode, err_blk, EIO,
@@ -4551,7 +4555,7 @@ int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc)
 int ext4_get_fc_inode_loc(struct super_block *sb, unsigned long ino,
                          struct ext4_iloc *iloc)
 {
-       return __ext4_get_inode_loc(sb, ino, iloc, 0, NULL);
+       return __ext4_get_inode_loc(sb, ino, NULL, iloc, NULL);
 }
 
 static bool ext4_should_enable_dax(struct inode *inode)