[Xen-changelog] [qemu-upstream-unstable] Add -f FMT / --format FMT arg to qemu-nbd

[patchbot@xxxxxxx]

commit 6dc71da698bfdc5297f8719e78eba26b1f15ff2c
Author:     Daniel P. Berrange <berrange@xxxxxxxxxx>
AuthorDate: Tue Oct 1 14:50:32 2013 +0000
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
CommitDate: Tue Oct 1 14:53:36 2013 +0000

    Add -f FMT / --format FMT arg to qemu-nbd
    
    Currently the qemu-nbd program will auto-detect the format of
    any disk it is given. This behaviour is known to be insecure.
    For example, if qemu-nbd initially exposes a 'raw' file to an
    unprivileged app, and that app runs
    
       'qemu-img create -f qcow2 -o backing_file=/etc/shadow /dev/nbd0'
    
    then the next time the app is started, the qemu-nbd will now
    detect it as a 'qcow2' file and expose /etc/shadow to the
    unprivileged app.
    
    The only way to avoid this is to explicitly tell qemu-nbd what
    disk format to use on the command line, completely disabling
    auto-detection. This patch adds a '-f' / '--format' arg for
    this purpose, mirroring what is already available via qemu-img
    and qemu commands.
    
      qemu-nbd --format raw -p 9000 evil.img
    
    will now always use raw, regardless of what format 'evil.img'
    looks like it contains
    
    upstream-commit-id: e6b636779b51c97e67694be740ee972c52460c59
    
    Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>
    [Use errx, not err. - Paolo]
    Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
    Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
 qemu-nbd.c    |   20 ++++++++++++++++++--
 qemu-nbd.texi |    2 ++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/qemu-nbd.c b/qemu-nbd.c
index 80f08d8..73d8833 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -305,6 +305,7 @@ static void nbd_accept(void *opaque)
 int main(int argc, char **argv)
 {
     BlockDriverState *bs;
+    BlockDriver *drv;
     off_t dev_offset = 0;
     uint32_t nbdflags = 0;
     bool disconnect = false;
@@ -312,7 +313,7 @@ int main(int argc, char **argv)
     char *device = NULL;
     int port = NBD_DEFAULT_PORT;
     off_t fd_size;
-    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:t";
+    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:t";
     struct option lopt[] = {
         { "help", 0, NULL, 'h' },
         { "version", 0, NULL, 'V' },
@@ -331,6 +332,7 @@ int main(int argc, char **argv)
         { "aio", 1, NULL, QEMU_NBD_OPT_AIO },
 #endif
         { "shared", 1, NULL, 'e' },
+        { "format", 1, NULL, 'f' },
         { "persistent", 0, NULL, 't' },
         { "verbose", 0, NULL, 'v' },
         { NULL, 0, NULL, 0 }
@@ -348,6 +350,7 @@ int main(int argc, char **argv)
     bool seen_aio = false;
 #endif
     pthread_t client_thread;
+    const char *fmt = NULL;
 
     /* The client thread uses SIGTERM to interrupt the server.  A signal
      * handler ensures that "qemu-nbd -v -c" exits with a nice status code.
@@ -442,6 +445,9 @@ int main(int argc, char **argv)
                 errx(EXIT_FAILURE, "Shared device number must be greater than 
0\n");
             }
             break;
+        case 'f':
+            fmt = optarg;
+            break;
        case 't':
            persistent = 1;
            break;
@@ -543,9 +549,19 @@ int main(int argc, char **argv)
     bdrv_init();
     atexit(bdrv_close_all);
 
+    if (fmt) {
+        drv = bdrv_find_format(fmt);
+        if (!drv) {
+            errx(EXIT_FAILURE, "Unknown file format '%s'", fmt);
+        }
+    } else {
+        drv = NULL;
+    }
+
     bs = bdrv_new("hda");
     srcpath = argv[optind];
-    if ((ret = bdrv_open(bs, srcpath, flags, NULL)) < 0) {
+    ret = bdrv_open(bs, srcpath, flags, drv);
+    if (ret < 0) {
         errno = -ret;
         err(EXIT_FAILURE, "Failed to bdrv_open '%s'", argv[optind]);
     }
diff --git a/qemu-nbd.texi b/qemu-nbd.texi
index 6955d90..70abfeb 100644
--- a/qemu-nbd.texi
+++ b/qemu-nbd.texi
@@ -36,6 +36,8 @@ Export QEMU disk image using NBD protocol.
   disconnect the specified device
 @item -e, --shared=@var{num}
   device can be shared by @var{num} clients (default @samp{1})
+@item -f, --format=@var{fmt}
+  force block driver for format @var{fmt} instead of auto-detecting
 @item -t, --persistent
   don't exit on the last connection
 @item -v, --verbose
--
generated by git-patchbot for /home/xen/git/qemu-upstream-unstable.git

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