From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Andrey Wagin <avagin@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>
Cc: linux-next@vger.kernel.org, linux-mm@kvack.org
Subject: Re: linux-next: Unable to write into a vma if it has been mapped without PROT_READ
Date: Mon, 29 Feb 2016 23:15:59 +0300 [thread overview]
Message-ID: <20160229201559.GB13188@node.shutemov.name> (raw)
In-Reply-To: <CANaxB-wA_3qh78NUBc2ODqYHyXJLK0O6FRCdWizXBRPpWoBaGQ@mail.gmail.com>
On Mon, Feb 29, 2016 at 11:11:37AM -0800, Andrey Wagin wrote:
> Hello Everyone,
>
> I found that now we can't write into a vma if it was mapped without PROT_READ:
>
> mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2ac7eb8000
> --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_ACCERR, si_addr=0x7f2ac7eb8000} ---
> +++ killed by SIGSEGV (core dumped) +++
> Segmentation fault
> [root@linux-next-test ~]# cat test.c
> #include <sys/mman.h>
> #include <stdlib.h>
>
> int main()
> {
> int *p;
>
> p = mmap(NULL, 4096, PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> p[0] = 1;
>
> return 0;
> }
>
> [root@linux-next-test ~]# uname -a
> Linux linux-next-test 4.5.0-rc6-next-20160229 #1 SMP Mon Feb 29
> 17:38:25 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
>
> This issue appeared in 4.5.0-rc5-next-20160226.
>
> https://ci.openvz.org/job/CRIU-linux-next/152/console
Looks like the regression is caused by change in access_error() by commit
62b5f7d013fc ("mm/core, x86/mm/pkeys: Add execute-only protection keys support")
as per next-20160229.
/*
* Assume all accesses require either read or execute
* permissions. This is not an instruction access, so
* it requires read permissions.
*/
if (!(vma->vm_flags & VM_READ))
return 1;
The assumption is false, taking this testcase into account.
Dave?
--
Kirill A. Shutemov
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-02-29 20:16 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-29 19:11 linux-next: Unable to write into a vma if it has been mapped without PROT_READ Andrey Wagin
2016-02-29 20:15 ` Kirill A. Shutemov [this message]
2016-03-01 1:00 ` Dave Hansen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160229201559.GB13188@node.shutemov.name \
--to=kirill@shutemov.name \
--cc=avagin@gmail.com \
--cc=dave.hansen@linux.intel.com \
--cc=linux-mm@kvack.org \
--cc=linux-next@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).