From a5068244b4f0c994791303b6186b6f732adab6c2 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Mon, 7 Nov 2016 14:38:13 -0600 Subject: [PATCH] nbd: Don't inf-loop on early EOF Commit 7d3123e 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: Max Reitz Signed-off-by: Eric Blake Message-Id: <1478551093-32757-1-git-send-email-eblake@redhat.com> Signed-off-by: Paolo Bonzini --- nbd/client.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/nbd/client.c b/nbd/client.c index 7db4301d29..ffb0743bce 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -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) {