Re: [PATCH 1/2] jbd2: check bh->b_data for NULL in jbd2_journal_get_descriptor_buffer before memset()

[Theodore Ts'o <tytso@mit.edu>]

On Mon, Jun 03, 2013 at 01:00:15PM +0300, Ruslan Bilovol wrote:
> The memset() doesn't perform any NULL-pointer checking
> before dereferencing passed pointer so this should be
> checked before calling it.

I can see that __getblk() can return NULL if there is a memory
allocation failure (and is defined to do so), so checking to make sure
bh is not NULL is a good thing to do.

Have you actually seen a case where bh is non-NULL, but bh->b_data is
NULL?  If not, it might be better to do something like this:

>  	bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
	if (!bh)
		return NULL;
	BUG_ON(!bh->b_data);

						- Ted