| From | Linus Torvalds <> | Date | Sat, 9 May 2020 13:16:53 -0700 | Subject | Re: [PATCH 3/5] exec: Remove recursion from search_binary_handler |
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On Sat, May 9, 2020 at 12:45 PM Eric W. Biederman <ebiederm@xmission.com> wrote: > > Instead of recursing in search_binary_handler have the methods that > would recurse return a positive value, and simply loop in exec_binprm. > > This is a trivial change as all of the methods that would recurse do > so as effectively the last thing they do. Making this a trivial code > change.
Looks good.
I'd suggest doing that loop slightly differently:
> - ret = search_binary_handler(bprm); > + do { > + depth++; > + ret = search_binary_handler(bprm); > + /* This allows 4 levels of binfmt rewrites before failing hard. */ > + if ((ret > 0) && (depth > 5)) > + ret = -ELOOP; > + } while (ret > 0); > if (ret >= 0) {
That's really an odd way to write this.
So honestly, if "ret < 0", then we can just return directly.
So I think would make much more sense to do this loop something like
for (depth = 0; depth < 5; depth++) { int ret;
ret = search_binary_handler(bprm); if (ret < 0) return ret;
/* Continue searching for the next binary handler? */ if (ret > 0) continue;
/* Success! */ audit_bprm(bprm); trace_sched_process_exec(current, old_pid, bprm); ptrace_event(PTRACE_EVENT_EXEC, old_vpid); proc_exec_connector(current); return 0; } return -ELOOP;
(if I read the logic of exec_binprm() right - I might have missed something).
Linus
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