[PATCH] Prevent git blame from segfaulting on a missing author name

David Reiss· Dec 22, 2009, 04:22 UTC · lore

The author name should never be missing in a valid commit, but git shouldn't segfault no matter what is in the object database.

Signed-off-by: David Reiss <dreiss@facebook.com>
---
git blame was segfaulting on a repro produced by piping mtn git_export
from the Pidgin repository to git fast-import.  This was the most obvious
fix, but I'm not sure if it is the best solution.

Here's a script that reproduces the segfault.

#!/bin/sh set -e git init echo line > afile git add afile TREE=`git write-tree` cat >badcommit <<EOF tree $TREE author <noname> 1234567890 +0000 committer David Reiss <dreiss@facebook.com> 1234567890 +0000

some message EOF COMMIT=`git hash-object -t commit -w badcommit` echo "git --no-pager blame $COMMIT -- afile" git --no-pager blame $COMMIT -- afile

 builtin-blame.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

Show changes to builtin-blame.c +1 −1

diff --git a/builtin-blame.c b/builtin-blame.c
index d4e25a5..5e19c79 100644
--- a/builtin-blame.c
+++ b/builtin-blame.c
@@ -1326,7 +1326,7 @@ static void get_ac_line(const char *inbuf, const char *what,
 	timepos = tmp;
 
 	*tmp = 0;
-	while (*tmp != ' ')
+	while (tmp > person && *tmp != ' ')
 		tmp--;
 	mailpos = tmp + 1;
 	*tmp = 0;

-- 
1.6.3.3

Junio C Hamano· Dec 22, 2009, 07:25 UTC · re: David Reiss · lore

Re: [PATCH] Prevent git blame from segfaulting on a missing author name

David Reiss <dreiss@facebook.com> writes:

Show 8 quoted lines

> The author name should never be missing in a valid commit, but
> git shouldn't segfault no matter what is in the object database.
>
> Signed-off-by: David Reiss <dreiss@facebook.com>
> ---
> git blame was segfaulting on a repro produced by piping mtn git_export
> from the Pidgin repository to git fast-import.  This was the most obvious
> fix, but I'm not sure if it is the best solution.

Thanks.

While it is _unusual_ not to have a human readable name, if the commits come from foreign systems (e.g. CVS/SVN), there often are not sufficient information in the source to fabricate names, so we should tolerate them.

We might want to also teach fast-import to warn when asked (i.e. when we are feeding from a foreign interface that is designed to read from a source that is capable of recording real names), but we shouldn't prevent it from creating such a commit.

> Here's a script that reproduces the segfault.

Please make that into a new test in an existing test suite somewhere in t/ directory.

I think we probably should prepare ourselves to be fed with even more broken commits, perhaps like this, if we are fixing it..

 builtin-blame.c |   13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)

Show changes to builtin-blame.c +10 −3

diff --git a/builtin-blame.c b/builtin-blame.c
index d4e25a5..14830a3 100644
--- a/builtin-blame.c
+++ b/builtin-blame.c
@@ -1305,6 +1305,7 @@ static void get_ac_line(const char *inbuf, const char *what,
 	error_out:
 		/* Ugh */
 		*tz = "(unknown)";
+		strcpy(person, *tz);
 		strcpy(mail, *tz);
 		*time = 0;
 		return;
@@ -1314,20 +1315,26 @@ static void get_ac_line(const char *inbuf, const char *what,
 	tmp = person;
 	tmp += len;
 	*tmp = 0;
-	while (*tmp != ' ')
+	while (person < tmp && *tmp != ' ')
 		tmp--;
+	if (tmp == person)
+		goto error_out;
 	*tz = tmp+1;
 	tzlen = (person+len)-(tmp+1);
 
 	*tmp = 0;
-	while (*tmp != ' ')
+	while (person < tmp && *tmp != ' ')
 		tmp--;
+	if (tmp == person)
+		goto error_out;
 	*time = strtoul(tmp, NULL, 10);
 	timepos = tmp;
 
 	*tmp = 0;
-	while (*tmp != ' ')
+	while (person < tmp && *tmp != ' ')
 		tmp--;
+	if (tmp <= person)
+		return;
 	mailpos = tmp + 1;
 	*tmp = 0;
 	maillen = timepos - tmp;

patchPrevent git blame from segfaulting on a missing author name