From: Dan Carpenter <dan.carpenter@oracle.com>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
security@kernel.org, ben.dooks@codethink.co.uk
Subject: Re: [PATCH] exec: warn if process starts with executable stack
Date: Tue, 19 Nov 2019 08:32:30 +0300 [thread overview]
Message-ID: <20191119053230.GC5626@kadam> (raw)
In-Reply-To: <20191118215227.GA24536@avx2>
On Tue, Nov 19, 2019 at 12:52:27AM +0300, Alexey Dobriyan wrote:
> There were few episodes of silent downgrade to an executable stack:
>
> 1) linking innocent looking assembly file
>
> $ cat f.S
> .intel_syntax noprefix
> .text
> .globl f
> f:
> ret
>
> $ cat main.c
> void f(void);
> int main(void)
> {
> f();
> return 0;
> }
>
> $ gcc main.c f.S
> $ readelf -l ./a.out
> GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000
> 0x0000000000000000 0x0000000000000000 RWE 0x10
>
> 2) converting C99 nested function into a closure
> https://nullprogram.com/blog/2019/11/15/
>
> void intsort2(int *base, size_t nmemb, _Bool invert)
> {
> int cmp(const void *a, const void *b)
> {
> int r = *(int *)a - *(int *)b;
> return invert ? -r : r;
> }
> qsort(base, nmemb, sizeof(*base), cmp);
> }
>
> will silently require stack trampolines while non-closure version will not.
>
> While without a double this behaviour is documented somewhere, add a warning
^^^^^^
doubt
> so that developers and users can at least notice. After so many years of x86_64
> having proper executable stack support it should not cause too much problems.
>
> If the system is old or CPU is old, then there will be an early warning
> against init and/or support personnel will write that "uh-oh, our Enterprise
> Software absolutely requires executable stack" and close tickets and customers
> will nod heads and life moves on.
>
regards,
dan carpenter
next prev parent reply other threads:[~2019-11-19 5:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-18 14:51 [PATCH] ELF: warn if process starts with executable stack Alexey Dobriyan
2019-11-18 17:13 ` Ben Dooks
2019-11-18 20:54 ` Andrew Morton
2019-11-18 21:36 ` Alexey Dobriyan
2019-11-18 21:52 ` [PATCH] exec: " Alexey Dobriyan
2019-11-19 5:32 ` Dan Carpenter [this message]
2019-11-20 19:17 ` Will Deacon
2019-11-20 20:28 ` Eric W. Biederman
2019-11-21 9:38 ` Will Deacon
2019-12-08 16:43 ` Alexey Dobriyan
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