Messages in this thread | | | Date | Thu, 14 Feb 2019 17:08:21 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] exec: load_script: Allow interpreter argument truncation |
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On 02/13, Kees Cook wrote: > > While we want to make sure the kernel doesn't attempt to execute a > truncated interpreter path, we must allow the interpreter arguments to > be truncated. Perl, for example, will re-read the script itself to parse > arguments correctly.
Heh. I still think that 8099b047ecc4 does the right thing.
But I can't argue with the fact that it caused the regression, so it should be reverted.
> This documents the parsing steps, and will fail to exec if the string was > truncated with neither an end-of-line nor any trailing whitespace.
You know, I have already spent 3 hours trying to write something simple and clear, but failed. Still trying...
Nor I can really understand your fix ;) Will try to read it again, just one question for now,
> for (cp = bprm->buf+2;; cp++) { > - if (cp >= bprm->buf + BINPRM_BUF_SIZE) > - return -ENOEXEC; > - if (!*cp || (*cp == '\n')) > + if (cp == bprm->buf + BINPRM_BUF_SIZE - 1) { > + truncated = true;
Off-by-one, no? "bprm->buf + BINPRM_BUF_SIZE - 1" is the very last char, it can be '\n' or '\0', this should set end_of_interp.
> break; > + } > + if (!*cp || (*cp == '\n')) { > + end_of_interp = true; > + break; > + }
so unless I am totally confused you should move this block up before the "bprm->buf + BINPRM_BUF_SIZE - 1" check or that check should use "bprm->buf + BINPRM_BUF_SIZE".
No?
Oleg.
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