[PATCH 4.19 134/205] ext4: missing !bh check in ext4_xattr_inode_write()

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vasily Averin <redacted>

commit eb6984fa4ce2837dcb1f66720a600f31b0bb3739 upstream.

According to Ted Ts'o ext4_getblk() called in ext4_xattr_inode_write()
should not return bh = NULL

The only time that bh could be NULL, then, would be in the case of
something really going wrong; a programming error elsewhere (perhaps a
wild pointer dereference) or I/O error causing on-disk file system
corruption (although that would be highly unlikely given that we had
*just* allocated the blocks and so the metadata blocks in question
probably would still be in the cache).

Fixes: e50e5129f384 ("ext4: xattr-in-inode support")
Signed-off-by: Vasily Averin <redacted>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 4.13
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/ext4/xattr.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c

@@ -1388,6 +1388,12 @@ retry:
 		bh = ext4_getblk(handle, ea_inode, block, 0);
 		if (IS_ERR(bh))
 			return PTR_ERR(bh);
+		if (!bh) {
+			WARN_ON_ONCE(1);
+			EXT4_ERROR_INODE(ea_inode,
+					 "ext4_getblk() return bh = NULL");
+			return -EFSCORRUPTED;
+		}
 		ret = ext4_journal_get_write_access(handle, bh);
 		if (ret)
 			goto out;