From: Eric Sandeen Date: Mon, 12 Oct 2015 05:04:15 +0000 (+1100) Subject: xfs: avoid null *src in memcpy call in xlog_write X-Git-Tag: firefly_0821_release~176^2~707^2~6^2 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=91f9f5fe1e7350e872b3fbc3194e8183bddce514;p=firefly-linux-kernel-4.4.55.git 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 Signed-off-by: Dave Chinner Reviewed-by: Eric Sandeen Signed-off-by: Dave Chinner --- diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index 0c8ef767c3a9..af08326b0e41 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -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); - memcpy(ptr, reg->i_addr + copy_off, copy_len); - xlog_write_adv_cnt(&ptr, &len, &log_offset, copy_len); - + if (copy_len > 0) { + 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); record_cnt++; data_cnt += contwr ? copy_len : 0;