From: Thomas Gleixner <tglx@linutronix.de>
To: Dmitry Safonov <dsafonov@virtuozzo.com>
Cc: linux-kernel@vger.kernel.org, 0x7f454c46@gmail.com,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@suse.de>,
x86@kernel.org, linux-mm@kvack.org
Subject: Re: [PATCHv4 4/5] x86/mm: check in_compat_syscall() instead TIF_ADDR32 for mmap(MAP_32BIT)
Date: Sat, 11 Feb 2017 21:13:01 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1702112107490.3734@nanos> (raw)
In-Reply-To: <20170130120432.6716-5-dsafonov@virtuozzo.com>
On Mon, 30 Jan 2017, Dmitry Safonov wrote:
> At this momet, logic in arch_get_unmapped_area{,_topdown} for mmaps with
> MAP_32BIT flag checks TIF_ADDR32 which means:
> o if 32-bit ELF changes mode to 64-bit on x86_64 and then tries to
> mmap() with MAP_32BIT it'll result in addr over 4Gb (as default is
> top-down allocation)
> o if 64-bit ELF changes mode to 32-bit and tries mmap() with MAP_32BIT,
> it'll allocate only memory in 1GB space: [0x40000000, 0x80000000).
>
> Fix it by handeling MAP_32BIT in 64-bit syscalls only.
I really have a hard time to understand what is fixed and how that is
related to the $subject.
Again. Please explain the problem first properly so one can understand the
issue immediately.
> As a little bonus it'll make thread flag a little less used.
I really do not understand the bonus part here. You replace the thread flag
check with a different one and AFAICT this looks like oart of the 'fix'.
Thanks,
tglx
> @@ -101,7 +101,7 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
> static void find_start_end(unsigned long flags, unsigned long *begin,
> unsigned long *end)
> {
> - if (!test_thread_flag(TIF_ADDR32) && (flags & MAP_32BIT)) {
> + if (!in_compat_syscall() && (flags & MAP_32BIT)) {
> /* This is usually used needed to map code in small
> model, so it needs to be in the first 31bit. Limit
> it to that. This means we need to move the
> @@ -195,7 +195,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
> return addr;
>
> /* for MAP_32BIT mappings we force the legacy mmap base */
> - if (!test_thread_flag(TIF_ADDR32) && (flags & MAP_32BIT))
> + if (!in_compat_syscall() && (flags & MAP_32BIT))
> goto bottomup;
>
> /* requesting a specific address */
> --
> 2.11.0
>
>
next prev parent reply other threads:[~2017-02-11 20:13 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-30 12:04 [PATCHv4 0/5] Fix compatible mmap() return pointer over 4Gb Dmitry Safonov
2017-01-30 12:04 ` [PATCHv4 1/5] x86/mm: split arch_mmap_rnd() on compat/native versions Dmitry Safonov
2017-02-09 13:55 ` Borislav Petkov
2017-02-09 23:06 ` Andy Lutomirski
2017-02-10 20:10 ` Thomas Gleixner
2017-02-10 20:25 ` Borislav Petkov
2017-02-10 21:28 ` Dmitry Safonov
2017-02-11 8:23 ` Thomas Gleixner
2017-02-13 11:12 ` Dmitry Safonov
2017-02-13 11:22 ` Thomas Gleixner
2017-01-30 12:04 ` [PATCHv4 2/5] x86/mm: introduce mmap{,_legacy}_base Dmitry Safonov
2017-02-11 14:13 ` Thomas Gleixner
2017-02-13 13:02 ` Dmitry Safonov
2017-02-13 13:13 ` Thomas Gleixner
2017-02-13 14:37 ` Dmitry Safonov
2017-02-13 15:35 ` Thomas Gleixner
2017-01-30 12:04 ` [PATCHv4 3/5] x86/mm: fix 32-bit mmap() for 64-bit ELF Dmitry Safonov
2017-02-11 19:49 ` Thomas Gleixner
2017-02-14 15:24 ` Dmitry Safonov
2017-01-30 12:04 ` [PATCHv4 4/5] x86/mm: check in_compat_syscall() instead TIF_ADDR32 for mmap(MAP_32BIT) Dmitry Safonov
2017-02-11 20:13 ` Thomas Gleixner [this message]
2017-02-14 16:11 ` Dmitry Safonov
2017-02-14 16:14 ` Dmitry Safonov
2017-01-30 12:04 ` [PATCHv4 5/5] selftests/x86: add test to check compat mmap() return addr Dmitry Safonov
2017-02-06 16:46 ` [PATCHv4 0/5] Fix compatible mmap() return pointer over 4Gb Dmitry Safonov
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=alpine.DEB.2.20.1702112107490.3734@nanos \
--to=tglx@linutronix.de \
--cc=0x7f454c46@gmail.com \
--cc=bp@suse.de \
--cc=dsafonov@virtuozzo.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=x86@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).