From: "Bill O'Donnell" <billodo@redhat.com>
To: Eric Sandeen <sandeen@redhat.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH] xfs: avoid null *src in memcpy call in xlog_write
Date: Wed, 7 Oct 2015 11:48:48 -0500 [thread overview]
Message-ID: <20151007164848.GA22636@redhat.com> (raw)
In-Reply-To: <56154967.70100@redhat.com>
Looks good to me.
Reviewed-by: Bill O'Donnell <billodo@redhat.com>
On Wed, Oct 07, 2015 at 11:33:43AM -0500, Eric Sandeen wrote:
> The gcc undefined behavior sanitizer caught this; surely
> any sane memcpy implementation will no-op if size == 0,
> but behavior with a *src of NULL is technically undefined
> (declared nonnull), so avoid it here.
>
> We are actually in this situation frequently via
> xlog_commit_record(), because:
>
> struct xfs_log_iovec reg = {
> .i_addr = NULL,
> .i_len = 0,
> .i_type = XLOG_REG_TYPE_COMMIT,
> };
>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
>
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 4012523..8897fd1 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -2424,7 +2424,10 @@ xlog_write(
>
> /* copy region */
> ASSERT(copy_len >= 0);
> - memcpy(ptr, reg->i_addr + copy_off, copy_len);
> + ASSERT(reg->i_addr + copy_off > 0 || copy_len == 0);
> + /* size == 0 is ok, but *src == NULL is undefined */
> + if (reg->i_addr + copy_off)
> + memcpy(ptr, reg->i_addr + copy_off, copy_len);
> xlog_write_adv_cnt(&ptr, &len, &log_offset, copy_len);
>
> copy_len += start_rec_copy + sizeof(xlog_op_header_t);
>
> _______________________________________________
> xfs mailing list
> xfs@oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs
_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs
next prev parent reply other threads:[~2015-10-07 16:48 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-07 16:33 [PATCH] xfs: avoid null *src in memcpy call in xlog_write Eric Sandeen
2015-10-07 16:48 ` Bill O'Donnell [this message]
2015-10-07 21:24 ` Dave Chinner
2015-10-07 21:31 ` Eric Sandeen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20151007164848.GA22636@redhat.com \
--to=billodo@redhat.com \
--cc=sandeen@redhat.com \
--cc=xfs@oss.sgi.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox