Default "tar" umask..

[Linus Torvalds <torvalds@osdl.org>]

We just had a posting on the kernel security list where a person was 
upset that the 2.6.19.1 and .2 tar-files were apparently group and 
world-writable.

Now, the default kernel releases don't do that (at least any more), 
because I've got

	[tar]
		umask=022

in my git config file these days, but the stable team apparently doesn't.

Looking at some of the tar-files I have lying around, they all seem to 
have used that 022 umask, and maybe we should just change the git default 
to that?

Anybody who wants to, can get the zero umask by just using the config 
file, but maybe the default should be the common case, and the case that 
isn't as likely to be a security issue if you untar it.

GNU tar has a "--no-same-permissions" flag to use the user umask at untar 
time, but I think that's a GNU-tar specific feature (at least I can't see 
any short flag to do the same), and I have to admit that I've _never_ used 
it even though I've used "tar" a long time, so at least going by my 
personal experience, I'd say it's very uncommon for people to use it.

The trivial untested patch below should do it.

		Linus

---
diff --git a/archive-tar.c b/archive-tar.c
index af47fdc..d4a2fa4 100644
--- a/archive-tar.c
+++ b/archive-tar.c
@@ -15,7 +15,7 @@ static char block[BLOCKSIZE];
 static unsigned long offset;
 
 static time_t archive_time;
-static int tar_umask;
+static int tar_umask = 022;
 static int verbose;
 
 /* writes out the whole block, but only if it is full */