ext4: avoid deadlock when expanding inode size

When we need to move xattrs into external xattr block, we call
ext4_xattr_block_set() from ext4_expand_extra_isize_ea(). That may end
up calling ext4_mark_inode_dirty() again which will recurse back into
the inode expansion code leading to deadlocks.

Protect from recursion using EXT4_STATE_NO_EXPAND inode flag and move
its management into ext4_expand_extra_isize_ea() since its manipulation
is safe there (due to xattr_sem) from possible races with
ext4_xattr_set_handle() which plays with it as well.

CC: stable@vger.kernel.org   # 4.4.x
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 5a6277d80f7c01b4b0d09ad6845559a33678df22..13c95b290263a2b9b62b42ecce2c6ce1e4ed696a 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5466,8 +5466,6 @@ int ext4_mark_inode_dirty(handle_t *handle, struct inode *inode)
                                                      sbi->s_want_extra_isize,
                                                      iloc, handle);
                        if (ret) {
-                               ext4_set_inode_state(inode,
-                                                    EXT4_STATE_NO_EXPAND);
                                if (mnt_count !=
                                        le16_to_cpu(sbi->s_es->s_mnt_count)) {
                                        ext4_warning(inode->i_sb,

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index c893f00b6dc00f2af925da1298d154903336ea92..2eb935ca5d9effac8eef6a2284d33acc62ae509e 100644 (file)
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1358,12 +1358,14 @@ int ext4_expand_extra_isize_ea(struct inode *inode, int new_extra_isize,
        int isize_diff; /* How much do we need to grow i_extra_isize */
 
        down_write(&EXT4_I(inode)->xattr_sem);
+       /*
+        * Set EXT4_STATE_NO_EXPAND to avoid recursion when marking inode dirty
+        */
+       ext4_set_inode_state(inode, EXT4_STATE_NO_EXPAND);
 retry:
        isize_diff = new_extra_isize - EXT4_I(inode)->i_extra_isize;
-       if (EXT4_I(inode)->i_extra_isize >= new_extra_isize) {
-               up_write(&EXT4_I(inode)->xattr_sem);
-               return 0;
-       }
+       if (EXT4_I(inode)->i_extra_isize >= new_extra_isize)
+               goto out;
 
        header = IHDR(inode, raw_inode);
        entry = IFIRST(header);
@@ -1392,8 +1394,7 @@ retry:
                                (void *)header, total_ino,
                                inode->i_sb->s_blocksize);
                EXT4_I(inode)->i_extra_isize = new_extra_isize;
-               error = 0;
-               goto cleanup;
+               goto out;
        }
 
        /*
@@ -1553,6 +1554,8 @@ retry:
                kfree(bs);
        }
        brelse(bh);
+out:
+       ext4_clear_inode_state(inode, EXT4_STATE_NO_EXPAND);
        up_write(&EXT4_I(inode)->xattr_sem);
        return 0;
 
@@ -1564,6 +1567,10 @@ cleanup:
        kfree(is);
        kfree(bs);
        brelse(bh);
+       /*
+        * We deliberately leave EXT4_STATE_NO_EXPAND set here since inode
+        * size expansion failed.
+        */
        up_write(&EXT4_I(inode)->xattr_sem);
        return error;
 }