Commit 91f9f5fe authored Oct 12, 2015 by Eric Sandeen Committed by Dave Chinner Oct 12, 2015

xfs: avoid null *src in memcpy call in xlog_write



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,
        };

Reported-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

parent dbd5c8c9

fs/xfs/xfs_log.c

+13 −4

Original line number	Diff line number	Diff line
		@@ -2422,11 +2422,20 @@ xlog_write(
		&partial_copy_len);
		xlog_verify_dest_ptr(log, ptr);

		/* copy region */
		/*
		* Copy region.
		*
		* Unmount records just log an opheader, so can have
		* empty payloads with no data region to copy. Hence we
		* only copy the payload if the vector says it has data
		* to copy.
		*/
		ASSERT(copy_len >= 0);
		if (copy_len > 0) {
		memcpy(ptr, reg->i_addr + copy_off, copy_len);
		xlog_write_adv_cnt(&ptr, &len, &log_offset, copy_len);

		xlog_write_adv_cnt(&ptr, &len, &log_offset,
		copy_len);
		}
		copy_len += start_rec_copy + sizeof(xlog_op_header_t);
		record_cnt++;
		data_cnt += contwr ? copy_len : 0;