discard giant patches

We occasionally see giant patches come in, normally from libvirt
releases such as:
  http://libvirt.org/git/?p=libvirt.git;a=commit;h=0086221cb377c7a1c2df58b8ee5eb8223f989765

Patchwork looks at patches line by line, and this consumes tons of
memory and runs for hours blocking everything. This detects giant
patches and safely discards them.

Change-Id: I2403941c708c0923bbe143e783f5869da88f880d

1 files changed, 3 insertions, 0 deletions

diff --git a/gitrepo.py b/gitrepo.py
index b1464f7..977a0a8 100644
--- a/gitrepo.py
+++ b/gitrepo.py
@@ -128,4 +128,7 @@ class Repo(object):
         # the patchwork parser code operates character by character so we must
         # convert to unicode so it can be handled properly
         patch = patch.decode('utf-8', errors='replace')
+        # Don't try and process >5Mb patches, they flood the server
+        if len(patch) > 5000000:
+            raise MemoryError('patch too large to process: %d' % len(patch))
         return parse_patch(patch)[0]