[Qemu-devel] [PATCH v2] qemu-nbd: Shrink image size by specified offset

[Qemu-devel] [PATCH v2] qemu-nbd: Shrink image size by specified offset

[Tomáš Golembiovský]

When --offset is set the apparent device size has to be adjusted
accordingly. Otherwise client may request read/write beyond the file end
which would fail.

Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>
---
 qemu-nbd.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/qemu-nbd.c b/qemu-nbd.c
index 99297a5..705b95e 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -901,6 +901,14 @@ int main(int argc, char **argv)
         exit(EXIT_FAILURE);
     }
 
+    if (dev_offset >= fd_size) {
+        error_report("Offset (%lld) has to be smaller than the image size "
+                     "(%lld)",
+                     (long long int)dev_offset, (long long int)fd_size);
+        exit(EXIT_FAILURE);
+    }
+    fd_size -= dev_offset;
+
     if (partition != -1) {
         ret = find_partition(blk, partition, &dev_offset, &fd_size);
         if (ret < 0) {
-- 
2.10.0

v1 -> v2:
- cast off_t variables to type with known formatting flag

Re: [Qemu-devel] [PATCH v2] qemu-nbd: Shrink image size by specified offset

[Eric Blake]

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On 10/05/2016 04:40 PM, Tomáš Golembiovský wrote:
> When --offset is set the apparent device size has to be adjusted
> accordingly. Otherwise client may request read/write beyond the file end
> which would fail.
> 
> Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>
> ---
>  qemu-nbd.c | 8 ++++++++
>  1 file changed, 8 insertions(+)

Reviewed-by: Eric Blake <eblake@redhat.com>

> 
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 99297a5..705b95e 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -901,6 +901,14 @@ int main(int argc, char **argv)
>          exit(EXIT_FAILURE);
>      }
>  
> +    if (dev_offset >= fd_size) {
> +        error_report("Offset (%lld) has to be smaller than the image size "
> +                     "(%lld)",
> +                     (long long int)dev_offset, (long long int)fd_size);
> +        exit(EXIT_FAILURE);
> +    }
> +    fd_size -= dev_offset;
> +
>      if (partition != -1) {
>          ret = find_partition(blk, partition, &dev_offset, &fd_size);
>          if (ret < 0) {
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH v2] qemu-nbd: Shrink image size by specified offset

[Paolo Bonzini]

On 05/10/2016 23:40, Tomáš Golembiovský wrote:
> When --offset is set the apparent device size has to be adjusted
> accordingly. Otherwise client may request read/write beyond the file end
> which would fail.
> 
> Signed-off-by: Tomáš Golembiovský <tgolembi@redhat.com>

Queued, thanks.

Paolo

> ---
>  qemu-nbd.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 99297a5..705b95e 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -901,6 +901,14 @@ int main(int argc, char **argv)
>          exit(EXIT_FAILURE);
>      }
>  
> +    if (dev_offset >= fd_size) {
> +        error_report("Offset (%lld) has to be smaller than the image size "
> +                     "(%lld)",
> +                     (long long int)dev_offset, (long long int)fd_size);
> +        exit(EXIT_FAILURE);
> +    }
> +    fd_size -= dev_offset;
> +
>      if (partition != -1) {
>          ret = find_partition(blk, partition, &dev_offset, &fd_size);
>          if (ret < 0) {
>