ext4: missing !bh check in ext4_xattr_inode_write()

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 <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 4.13
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index f36fc5d5b257438666641028b8660c0ce3462e91..302725176571b5ed3f94bc9a68a0eccee7158e24 100644 (file)
--- 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;