Commit a5068244 authored by Eric Blake's avatar Eric Blake Committed by Paolo Bonzini
Browse files

nbd: Don't inf-loop on early EOF 



Commit 7d3123e1 converted a single read_sync() into a while loop
that assumed that read_sync() would either make progress or give
an error. But when the server hangs up early, the client sees
EOF (a read_sync() of 0) and never makes progress, which in turn
caused qemu-iotest './check -nbd 83' to go into an infinite loop.

Rework the loop to accomodate reads cut short by EOF.

Reported-by: default avatarMax Reitz <mreitz@redhat.com>
Signed-off-by: default avatarEric Blake <eblake@redhat.com>
Message-Id: <1478551093-32757-1-git-send-email-eblake@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 175cad36

nbd/client.c

+7 −6
Original line number Diff line number Diff line
@@ -90,20 +90,21 @@ static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports); 
 * the amount of bytes consumed. */

static ssize_t drop_sync(QIOChannel *ioc, size_t size)

{

    ssize_t ret, dropped = size;

    ssize_t ret = 0;

    char small[1024];

    char *buffer;



    buffer = sizeof(small) < size ? small : g_malloc(MIN(65536, size));

    while (size > 0) {

        ret = read_sync(ioc, buffer, MIN(65536, size));

        if (ret < 0) {

        ssize_t count = read_sync(ioc, buffer, MIN(65536, size));



        if (count <= 0) {

            goto cleanup;

        }

        assert(ret <= size);

        size -= ret;

        assert(count <= size);

        size -= count;

        ret += count;

    }

    ret = dropped;



 cleanup:

    if (buffer != small) {