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Re: [Qemu-block] [PATCH v2 34/36] block: Fail bdrv_truncate() with negat

From: Eric Blake
Subject: Re: [Qemu-block] [PATCH v2 34/36] block: Fail bdrv_truncate() with negative size
Date: Thu, 22 Feb 2018 17:35:57 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0

On 02/21/2018 07:54 AM, Kevin Wolf wrote:
Most callers have their own checks, but something like this should also
be checked centrally. As it happens, x-blockdev-create can pass negative
image sizes to format drivers (because there is no QAPI type that would
reject negative numbers) and triggers the check added by this patch.

Signed-off-by: Kevin Wolf <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
  block.c | 5 +++++
  1 file changed, 5 insertions(+)

Are there any callers that can be simplified (such as now assert()ing rather than checking and returning an error) due to better guarantees about a non-negative argument?

diff --git a/block.c b/block.c
index 4a7e448226..5c874aefa1 100644
--- a/block.c
+++ b/block.c
@@ -3684,6 +3684,11 @@ int bdrv_truncate(BdrvChild *child, int64_t offset, 
PreallocMode prealloc,
          error_setg(errp, "No medium inserted");
          return -ENOMEDIUM;
+    if (offset < 0) {
+        error_setg(errp, "Image size cannot be negative");
+        return -EINVAL;
+    }
      if (!drv->bdrv_truncate) {
          if (bs->file && drv->is_filter) {
              return bdrv_truncate(bs->file, offset, prealloc, errp);

Reviewed-by: Eric Blake <address@hidden>

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

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