From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <sourceware-bugzilla@sourceware.org>
Received: by sourceware.org (Postfix, from userid 48)
	id C80CA3858C56; Wed, 28 Sep 2022 10:31:57 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C80CA3858C56
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org;
	s=default; t=1664361117;
	bh=hqqq6OyIe8DD/z6iNFIYX/cMJD+1KFrEGr98/M+vMAk=;
	h=From:To:Subject:Date:From;
	b=OEIHjtnwFoKxucPOYP2UKDfKEZTkYlENWrFA4oyVbT3xH93gbMJlzHBOslkMvHk98
	 DvFltIHPuil9/lONRN348a0e/5sQqONyLsMPtor7MYSSHkPgi+VOlgBt8kcC50I0p1
	 5N6iivyx6o0inHe8ZhX3fDp8tFBVifujrm7/mOd4=
From: "ycliang at andestech dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug malloc/29624] New: errno is not cleared when entering main
Date: Wed, 28 Sep 2022 10:31:56 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: glibc
X-Bugzilla-Component: malloc
X-Bugzilla-Version: 2.35
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: ycliang at andestech dot com
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: unassigned at sourceware dot org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-29624-131@http.sourceware.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://sourceware.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <glibc-bugs.sourceware.org>

https://sourceware.org/bugzilla/show_bug.cgi?id=3D29624

            Bug ID: 29624
           Summary: errno is not cleared when entering main
           Product: glibc
           Version: 2.35
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: malloc
          Assignee: unassigned at sourceware dot org
          Reporter: ycliang at andestech dot com
  Target Milestone: ---

According to the ANSI C standard "7.5 Errors <errno.h>" section 3[1],=20
"The value of errno is zero at program startup,
but is never set to zero by any library function."

The "program startup" is also defined in ANSI C standard=20
"5.1.2.2.1 Program startup" section 1[2],
"The function called at program startup is named main."

Therefore, it should be reasonable to expect=20
errno be zero when main is executed.

However, we found that=20
the following program would get non-zero errno under some circumstances.

```
/* errno.c */
#include <errno.h>
#include <stdio.h>

int main()
{
        printf("errno: %d\n", errno);
        return 0;
}


$ riscv64-linux-gcc -O0 -g -static -o errno_st errno.c

[   51.968765] random: fast init done
/mnt # ./errno
errno: 11

[   51.968765] random: fast init done
[  262.517056] crng init done
/mnt # ./errno
errno: 0
```

If the above program is statically-linked,=20
and if the program is executed before "crng init done",
the errno will not be zero when entering main.

There seems to be syscall (__getrandom) before main is entered,
and if the crng is not initialized,=20
the syscall will fail causing the errno to be set.
(_dl_get_origin -> __libc_malloc -> ptmalloc_init -> tcache_key_initialize =
->
__getrandom)

Thanks to Florian's suggestion:
"Hiding the getrandom failure is probably sufficient.  All other
failures in malloc will lead to the process failing to start, so those
errors don't need to be masked."

We should clear the errno for the getrandom failure

Related discussion:
https://sourceware.org/pipermail/libc-help/2022-September/006301.html

--=20
You are receiving this mail because:
You are on the CC list for the bug.=