Re: [patch] strtok.3 add note about glibc-2.25+ segfault for call like strtok_r(NULL,"|",NULL)

From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
To: Marcin Stolarek <stolarek.marcin@gmail.com>,
	"mtk.manpages@gmail.com" <mtk.manpages@gmail.com>
Cc: linux-man <linux-man@vger.kernel.org>
Subject: Re: [patch] strtok.3 add note about glibc-2.25+ segfault for call like strtok_r(NULL,"|",NULL)
Date: Sat, 25 Apr 2020 16:54:45 +0000	[thread overview]
Message-ID: <DB8PR08MB50360CF57C6AD1A2C7EEB43A83D10@DB8PR08MB5036.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <CAC8K6BP1TFVjQRxs873FUCBNdOVNAkb+d1exd41Q_CTUvCjnSw@mail.gmail.com>

Hi,

> It worked fine prior to 2.25, since it's a change I thoight it may be nice to document that this set
> of arguments will segfault and has to be avoided by calling app itself.

Did it ever? Even much older versions have always accessed *save_ptr with a NULL input, so a crash
is guaranteed. And *s is also always accessed, so it had better never be NULL. Eg. this is what it did
back in 2007 ([1]):

  if (s == NULL)
    s = *save_ptr;  // crash here

  /* Scan leading delimiters.  */
  s += strspn (s, delim);
  if (*s == '\0')
    {
      *save_ptr = s;
      return NULL;
    }

Cheers,
Wilco

[1] https://github.com/bminor/glibc/blob/0ecb606cb6cf65de1d9fc8a919bceb4be476c602/string/strtok_r.c

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