Fix endless loop in apt-get update that can cause disk fillup

The apt http code parses Content-Length and Content-Range. For
both requests the variable "Size" is used and the semantic for
this Size is the total file size. However Content-Length is not
the entire file size for partital file requests. For servers that
send the Content-Range header first and then the Content-Length
header this can lead to globbing of Size so that its less than
the real file size. This may lead to a subsequent passing of a
negative number into the CircleBuf which leads to a endless
loop that writes data.

Thanks to Anton Blanchard for the analysis and initial patch.

LP: #1445239

1 files changed, 2 insertions, 1 deletions

diff --git a/methods/server.h b/methods/server.h
index 1b81e3549..ed3cb456a 100644
--- a/methods/server.h
+++ b/methods/server.h
@@ -34,7 +34,8 @@ struct ServerState
    char Code[360];
 
    // These are some statistics from the last parsed header lines
-   unsigned long long Size; // size of the usable content (aka: the file)
+   unsigned long long Size; // total size of the usable content (aka: the file)
+   unsigned long long DownloadSize; // size we actually download (can be smaller than Size if we have partial content)
    unsigned long long JunkSize; // size of junk content (aka: server error pages)
    unsigned long long StartPos;
    time_t Date;