Merge ~alexmurray/ubuntu-cve-tracker:optimise-cve-lib-get-long-kernel-hash into ubuntu-cve-tracker:master

[Alex Murray]

scripts/cve_lib.py: optimise get_long_kernel_hash()

The initial kernel git commit is a single huge commit which added the entire
2.6.12-rc2 kernel into the git repo - as such, fetching this takes a really long
time AND it is both a common Fixes: commit since it is used for anything which
has existed in the kernel since that time. So optimise for this case by checking
specifically if a short_hash matches this and just returning the known full
commit hash in that case without looking it up. Also for the general case, since
we really only need the first line of the commit patch body to get the "From "
line, just fetch the first 1k of the patch without waiting for the rest.

Signed-off-by: Alex Murray <email address hidden>

[Marc Deslauriers (mdeslaur)]

LGTM, thanks!

review: Approve

[Seth Arnold (seth-arnold)]

I like it; 12 chars might be too long for it to ever actually work in practice, but it's a very safe length :)

review: Approve

diff --git a/scripts/cve_lib.py b/scripts/cve_lib.py
index d8e274d..95c8f65 100755
--- a/scripts/cve_lib.py
+++ b/scripts/cve_lib.py
@@ -3571,10 +3571,24 @@ def in_break_fixes(commit, break_fixes):
 
 def get_long_kernel_hash(short_hash):
     '''Attempts to get a long kernel hash'''
+    # don't try and fetch the initial kernel git commit as this is huge
+    INITIAL_COMMIT_HASH="1da177e4c3f41524e886b7f1b8a0c1fc7321cac2"
+    # but we also don't want to match on a short_hash like '1' either so if we
+    # are going to use this short-cut ensure we have enough of a short_hash that
+    # it is likely unique
+    # [ $(git rev-parse --short $INITIAL_COMMIT_HASH | wc -c) -eq 13 ]
+    if len(short_hash) > 12 and INITIAL_COMMIT_HASH.startswith(short_hash):
+        return INITIAL_COMMIT_HASH
 
     url = 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/patch/?id=' + short_hash
     with urllib.request.urlopen(url) as response:
-       patch = response.read().decode('utf-8')
+        try:
+            # we only need the first line of the patch so limit to the first
+            # 1024 bytes
+            patch = response.read(1024).decode('utf-8')
+        except Exception as e:
+            print("Failed to fetch patch via url '%s': %s" % (url, str(e)), file=sys.stderr)
+            return short_hash
 
     for line in patch.split("\n"):
         if line.startswith("From "):