On Tue, Feb 01, 2022 at 09:17:47AM +0000, David Laight wrote:
From: Kees Cook
Sent: 01 February 2022 00:10
...
While the initial code searches[6][7] turned up what appeared to be mostly corner case tests, trying to that just reject argv == NULL (or an immediately terminated pointer list) quickly started tripping[8] existing userspace programs.
The next best approach is forcing a single empty string into argv and adjusting argc to match. The number of programs depending on argc == 0 seems a smaller set than those calling execve with a NULL argv.
Has anyone considered using the pathname for argv[0]? So converting: execl(path, NULL); into: execl(path, path, NULL);
I've not spotted any such suggestion.
It came up on some IRC discussions at some point. I'm personally not a fan of this because it creates a bit of "new" ABI that has a lot of variability (depending on "" is one thing, but depending on a "missing" argv matching the exec path is very different). I think there were also concerns about dealing with fd-based exec ("what is the 'right' name"), etc.
I'd prefer we stay as simple as possible for this change.