2013-09-03 19:03:25 +00:00
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From a5ecab4962d52e7dcec96c7e99bade769fb8cf8b Mon Sep 17 00:00:00 2001
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2013-04-21 00:14:03 +00:00
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From: "Daniel P. Berrange" <berrange@redhat.com>
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Date: Tue, 19 Mar 2013 11:20:20 +0000
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Subject: [PATCH] Add -f FMT / --format FMT arg to qemu-nbd
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Currently the qemu-nbd program will auto-detect the format of
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any disk it is given. This behaviour is known to be insecure.
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For example, if qemu-nbd initially exposes a 'raw' file to an
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unprivileged app, and that app runs
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'qemu-img create -f qcow2 -o backing_file=/etc/shadow /dev/nbd0'
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then the next time the app is started, the qemu-nbd will now
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detect it as a 'qcow2' file and expose /etc/shadow to the
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unprivileged app.
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The only way to avoid this is to explicitly tell qemu-nbd what
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disk format to use on the command line, completely disabling
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auto-detection. This patch adds a '-f' / '--format' arg for
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this purpose, mirroring what is already available via qemu-img
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and qemu commands.
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qemu-nbd --format raw -p 9000 evil.img
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will now always use raw, regardless of what format 'evil.img'
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looks like it contains
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Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
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[Use errx, not err. - Paolo]
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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(cherry picked from commit e6b636779b51c97e67694be740ee972c52460c59)
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Conflicts:
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qemu-nbd.c
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---
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qemu-nbd.c | 20 ++++++++++++++++++--
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qemu-nbd.texi | 2 ++
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2 files changed, 20 insertions(+), 2 deletions(-)
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diff --git a/qemu-nbd.c b/qemu-nbd.c
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index 1c1cf6a..abf654e 100644
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--- a/qemu-nbd.c
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+++ b/qemu-nbd.c
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@@ -291,6 +291,7 @@ static void nbd_accept(void *opaque)
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int main(int argc, char **argv)
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{
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BlockDriverState *bs;
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+ BlockDriver *drv;
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off_t dev_offset = 0;
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uint32_t nbdflags = 0;
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bool disconnect = false;
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@@ -298,7 +299,7 @@ int main(int argc, char **argv)
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char *device = NULL;
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int port = NBD_DEFAULT_PORT;
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off_t fd_size;
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- const char *sopt = "hVb:o:p:rsnP:c:dvk:e:t";
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+ const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:t";
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struct option lopt[] = {
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{ "help", 0, NULL, 'h' },
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{ "version", 0, NULL, 'V' },
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@@ -317,6 +318,7 @@ int main(int argc, char **argv)
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{ "aio", 1, NULL, QEMU_NBD_OPT_AIO },
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#endif
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{ "shared", 1, NULL, 'e' },
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+ { "format", 1, NULL, 'f' },
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{ "persistent", 0, NULL, 't' },
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{ "verbose", 0, NULL, 'v' },
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{ NULL, 0, NULL, 0 }
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@@ -335,6 +337,7 @@ int main(int argc, char **argv)
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bool seen_aio = false;
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#endif
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pthread_t client_thread;
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+ const char *fmt = NULL;
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/* The client thread uses SIGTERM to interrupt the server. A signal
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* handler ensures that "qemu-nbd -v -c" exits with a nice status code.
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@@ -429,6 +432,9 @@ int main(int argc, char **argv)
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errx(EXIT_FAILURE, "Shared device number must be greater than 0\n");
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}
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break;
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+ case 'f':
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+ fmt = optarg;
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+ break;
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case 't':
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persistent = 1;
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break;
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@@ -529,9 +535,19 @@ int main(int argc, char **argv)
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bdrv_init();
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atexit(bdrv_close_all);
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+ if (fmt) {
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+ drv = bdrv_find_format(fmt);
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+ if (!drv) {
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+ errx(EXIT_FAILURE, "Unknown file format '%s'", fmt);
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+ }
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+ } else {
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+ drv = NULL;
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+ }
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+
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bs = bdrv_new("hda");
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srcpath = argv[optind];
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- if ((ret = bdrv_open(bs, srcpath, flags, NULL)) < 0) {
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+ ret = bdrv_open(bs, srcpath, flags, drv);
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+ if (ret < 0) {
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errno = -ret;
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err(EXIT_FAILURE, "Failed to bdrv_open '%s'", argv[optind]);
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}
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diff --git a/qemu-nbd.texi b/qemu-nbd.texi
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index 6955d90..70abfeb 100644
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--- a/qemu-nbd.texi
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+++ b/qemu-nbd.texi
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@@ -36,6 +36,8 @@ Export QEMU disk image using NBD protocol.
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disconnect the specified device
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@item -e, --shared=@var{num}
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device can be shared by @var{num} clients (default @samp{1})
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+@item -f, --format=@var{fmt}
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+ force block driver for format @var{fmt} instead of auto-detecting
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@item -t, --persistent
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don't exit on the last connection
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@item -v, --verbose
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