Re: [libvirt] [PATCH] Eliminate large stack buffer in doTunnelSendAll

doTunnelSendAll function (used by QEMU migration) uses a 64k buffer on the stack, which could be problematic. This patch replaces that with a buffer from the heap.

While in the neighborhood, this patch also improves error reporting in the case that saferead fails - previously, virStreamAbort() was called (resetting errno) before reporting the error. It's been changed to report the error first.

- char buffer[65536]; - int nbytes = sizeof(buffer); + char *buffer; + int nbytes = TUNNEL_SEND_BUF_SIZE; + + if (VIR_ALLOC_N(buffer, TUNNEL_SEND_BUF_SIZE) < 0) { + virStreamAbort(st); + virReportOOMError();

+ return -1; + } /* XXX should honour the 'resource' parameter here */ for (;;) { nbytes = saferead(sock, buffer, nbytes); if (nbytes < 0) { - virStreamAbort(st); virReportSystemError(errno, "%s", _("tunnelled migration failed to read from qemu")); + virStreamAbort(st); + VIR_FREE(buffer);