On 20/09/2016 11:41, Tomáš Golembiovský wrote:
> When image is part of the file it makes sense to limit the length of the
> image in the file. Otherwise it is assumed that the image spans to the
> end of the file. This assumption may lead to reads/writes outside of the
> image and thus lead to errors or data corruption.
>
> To limit the assumed image size new option is introduced.
The patch makes sense, but I think the commit message is incorrect
because this bug is already fixed by patch 1. Also, the option in the
help is --device-size, not --image-size; I would just call it --size.
Thanks,
Paolo
>
> Signed-off-by: Tomáš Golembiovský <tgole...@redhat.com>
> ---
> qemu-nbd.c | 44 +++++++++++++++++++++++++++++++++++---------
> qemu-nbd.texi | 4 ++++
> 2 files changed, 39 insertions(+), 9 deletions(-)
>
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 629bce1..7ed52f7 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -85,6 +85,7 @@ static void usage(const char *name)
> "\n"
> "Exposing part of the image:\n"
> " -o, --offset=OFFSET offset into the image\n"
> +" -S, --device-size=LEN limit reported device size\n"
> " -P, --partition=NUM only expose partition NUM\n"
> "\n"
> "General purpose options:\n"
> @@ -471,10 +472,12 @@ int main(int argc, char **argv)
> const char *port = NULL;
> char *sockpath = NULL;
> char *device = NULL;
> - off_t fd_size;
> + off_t real_size = 0;
> + off_t fd_size = 0;
> + bool has_image_size = false;
> QemuOpts *sn_opts = NULL;
> const char *sn_id_or_name = NULL;
> - const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:x:T:";
> + const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:x:T:S:";
> struct option lopt[] = {
> { "help", no_argument, NULL, 'h' },
> { "version", no_argument, NULL, 'V' },
> @@ -482,6 +485,7 @@ int main(int argc, char **argv)
> { "port", required_argument, NULL, 'p' },
> { "socket", required_argument, NULL, 'k' },
> { "offset", required_argument, NULL, 'o' },
> + { "image-size", required_argument, NULL, 'S' },
> { "read-only", no_argument, NULL, 'r' },
> { "partition", required_argument, NULL, 'P' },
> { "connect", required_argument, NULL, 'c' },
> @@ -714,6 +718,18 @@ int main(int argc, char **argv)
> g_free(trace_file);
> trace_file = trace_opt_parse(optarg);
> break;
> + case 'S':
> + ret = qemu_strtoll(optarg, NULL, 0, &fd_size);
> + if (ret != 0) {
> + error_report("Invalid image size `%s'", optarg);
> + exit(EXIT_FAILURE);
> + }
> + if (fd_size <= 0) {
> + error_report("Image size must be positive `%s'", optarg);
> + exit(EXIT_FAILURE);
> + }
> + has_image_size = true;
> + break;
> }
> }
>
> @@ -894,19 +910,29 @@ int main(int argc, char **argv)
> }
>
> bs->detect_zeroes = detect_zeroes;
> - fd_size = blk_getlength(blk);
> - if (fd_size < 0) {
> + real_size = blk_getlength(blk);
> + if (real_size < 0) {
> error_report("Failed to determine the image length: %s",
> - strerror(-fd_size));
> + strerror(-real_size));
> exit(EXIT_FAILURE);
> }
>
> - if (dev_offset >= fd_size) {
> - error_report("Offset (%lu) has to be smaller than the image size
> (%lu)",
> - dev_offset, fd_size);
> + if (!has_image_size) {
> + fd_size = real_size;
> +
> + if (dev_offset >= fd_size) {
> + error_report("Offset (%lu) has to be smaller than image size
> (%lu)",
> + dev_offset, fd_size);
> + exit(EXIT_FAILURE);
> + }
> +
> + fd_size -= dev_offset;
> + } else if ((dev_offset + fd_size) > real_size) {
> + error_report("Offset (%lu) plus image size (%lu) has to be smaller "
> + "than or equal to real image size (%lu)",
> + dev_offset, fd_size, real_size);
> exit(EXIT_FAILURE);
> }
> - fd_size -= dev_offset;
>
> if (partition != -1) {
> ret = find_partition(blk, partition, &dev_offset, &fd_size);
> diff --git a/qemu-nbd.texi b/qemu-nbd.texi
> index 91ebf04..c589525 100644
> --- a/qemu-nbd.texi
> +++ b/qemu-nbd.texi
> @@ -30,6 +30,10 @@ credentials for the qemu-nbd server.
> The TCP port to listen on (default @samp{10809})
> @item -o, --offset=@var{offset}
> The offset into the image
> +@item -S, --image-size=@var{length}
> +The size of the image to present to client. This is useful in combination
> with
> +@var{-o} when the image is embedded in file but does not span to the end of
> the
> +file.
> @item -b, --bind=@var{iface}
> The interface to bind to (default @samp{0.0.0.0})
> @item -k, --socket=@var{path}
>
