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 3/5] x86/mm: fix 32-bit mmap() for 64-bit ELF Date: Sat, 11 Feb 2017 20:49:43 +0100 (CET) [thread overview] Message-ID: <alpine.DEB.2.20.1702111513460.3734@nanos> (raw) In-Reply-To: <20170130120432.6716-4-dsafonov@virtuozzo.com> On Mon, 30 Jan 2017, Dmitry Safonov wrote: > Fix 32-bit compat_sys_mmap() mapping VMA over 4Gb in 64-bit binaries > and 64-bit sys_mmap() mapping VMA only under 4Gb in 32-bit binaries. > Introduced new bases for compat syscalls in mm_struct: > mmap_compat_base and mmap_compat_legacy_base for top-down and > bottom-up allocations accordingly. > Taught arch_get_unmapped_area{,_topdown}() to use the new mmap_bases > in compat syscalls for high/low limits in vm_unmapped_area(). > > I discovered that bug on ZDTM tests for compat 32-bit C/R. > Working compat sys_mmap() in 64-bit binaries is really needed for that > purpose, as 32-bit applications are restored from 64-bit CRIU binary. Again that changelog sucks. Explain the problem/bug first. Then explain the way to fix it and do not tell fairy tales about what you did without explaing the bug in the first place. Documentation....SubittingPatches explains that very well. > +config HAVE_ARCH_COMPAT_MMAP_BASES > + bool > + help > + If this is set, one program can do native and compatible syscall > + mmap() on architecture. Thus kernel has different bases to > + compute high and low virtual address limits for allocation. Sigh. How is a user supposed to decode this? This allows 64bit applications to invoke syscalls in 64bit and 32bit mode. Required for .... > > @@ -113,10 +114,19 @@ static void find_start_end(unsigned long flags, unsigned long *begin, > if (current->flags & PF_RANDOMIZE) { > *begin = randomize_page(*begin, 0x02000000); > } > - } else { > - *begin = current->mm->mmap_legacy_base; > - *end = TASK_SIZE; > + return; > } > + > +#ifdef CONFIG_COMPAT Can you please find a solution which does not create that ifdef horror in the code? Just a few accessors to those compat fields are required to do that. > + > +#ifdef CONFIG_COMPAT > + arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base, > + arch_compat_rnd(), IA32_PAGE_OFFSET); > +#endif Ditto Thanks, tglx
WARNING: multiple messages have this Message-ID (diff)
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 3/5] x86/mm: fix 32-bit mmap() for 64-bit ELF Date: Sat, 11 Feb 2017 20:49:43 +0100 (CET) [thread overview] Message-ID: <alpine.DEB.2.20.1702111513460.3734@nanos> (raw) In-Reply-To: <20170130120432.6716-4-dsafonov@virtuozzo.com> On Mon, 30 Jan 2017, Dmitry Safonov wrote: > Fix 32-bit compat_sys_mmap() mapping VMA over 4Gb in 64-bit binaries > and 64-bit sys_mmap() mapping VMA only under 4Gb in 32-bit binaries. > Introduced new bases for compat syscalls in mm_struct: > mmap_compat_base and mmap_compat_legacy_base for top-down and > bottom-up allocations accordingly. > Taught arch_get_unmapped_area{,_topdown}() to use the new mmap_bases > in compat syscalls for high/low limits in vm_unmapped_area(). > > I discovered that bug on ZDTM tests for compat 32-bit C/R. > Working compat sys_mmap() in 64-bit binaries is really needed for that > purpose, as 32-bit applications are restored from 64-bit CRIU binary. Again that changelog sucks. Explain the problem/bug first. Then explain the way to fix it and do not tell fairy tales about what you did without explaing the bug in the first place. Documentation....SubittingPatches explains that very well. > +config HAVE_ARCH_COMPAT_MMAP_BASES > + bool > + help > + If this is set, one program can do native and compatible syscall > + mmap() on architecture. Thus kernel has different bases to > + compute high and low virtual address limits for allocation. Sigh. How is a user supposed to decode this? This allows 64bit applications to invoke syscalls in 64bit and 32bit mode. Required for .... > > @@ -113,10 +114,19 @@ static void find_start_end(unsigned long flags, unsigned long *begin, > if (current->flags & PF_RANDOMIZE) { > *begin = randomize_page(*begin, 0x02000000); > } > - } else { > - *begin = current->mm->mmap_legacy_base; > - *end = TASK_SIZE; > + return; > } > + > +#ifdef CONFIG_COMPAT Can you please find a solution which does not create that ifdef horror in the code? Just a few accessors to those compat fields are required to do that. > + > +#ifdef CONFIG_COMPAT > + arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base, > + arch_compat_rnd(), IA32_PAGE_OFFSET); > +#endif Ditto Thanks, tglx -- 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:[~2017-02-11 19:49 UTC|newest] Thread overview: 49+ 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 ` Dmitry Safonov 2017-01-30 12:04 ` [PATCHv4 1/5] x86/mm: split arch_mmap_rnd() on compat/native versions Dmitry Safonov 2017-01-30 12:04 ` Dmitry Safonov 2017-02-09 13:55 ` Borislav Petkov 2017-02-09 23:06 ` Andy Lutomirski 2017-02-09 23:06 ` Andy Lutomirski 2017-02-10 20:10 ` Thomas Gleixner 2017-02-10 20:10 ` Thomas Gleixner 2017-02-10 20:25 ` Borislav Petkov 2017-02-10 20:25 ` Borislav Petkov 2017-02-10 21:28 ` Dmitry Safonov 2017-02-10 21:28 ` Dmitry Safonov 2017-02-11 8:23 ` Thomas Gleixner 2017-02-11 8:23 ` Thomas Gleixner 2017-02-13 11:12 ` Dmitry Safonov 2017-02-13 11:12 ` Dmitry Safonov 2017-02-13 11:22 ` Thomas Gleixner 2017-02-13 11:22 ` Thomas Gleixner 2017-01-30 12:04 ` [PATCHv4 2/5] x86/mm: introduce mmap{,_legacy}_base Dmitry Safonov 2017-01-30 12:04 ` Dmitry Safonov 2017-02-11 14:13 ` Thomas Gleixner 2017-02-11 14:13 ` Thomas Gleixner 2017-02-13 13:02 ` Dmitry Safonov 2017-02-13 13:02 ` Dmitry Safonov 2017-02-13 13:13 ` Thomas Gleixner 2017-02-13 13:13 ` Thomas Gleixner 2017-02-13 14:37 ` Dmitry Safonov 2017-02-13 14:37 ` Dmitry Safonov 2017-02-13 15:35 ` Thomas Gleixner 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 2017-01-30 12:04 ` Dmitry Safonov 2017-02-11 19:49 ` Thomas Gleixner [this message] 2017-02-11 19:49 ` Thomas Gleixner 2017-02-14 15:24 ` Dmitry Safonov 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 2017-01-30 12:04 ` Dmitry Safonov 2017-02-11 20:13 ` Thomas Gleixner 2017-02-11 20:13 ` Thomas Gleixner 2017-02-14 16:11 ` Dmitry Safonov 2017-02-14 16:11 ` Dmitry Safonov 2017-02-14 16:14 ` 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 2017-01-30 12:04 ` Dmitry Safonov 2017-02-06 16:46 ` [PATCHv4 0/5] Fix compatible mmap() return pointer over 4Gb Dmitry Safonov 2017-02-06 16:46 ` Dmitry Safonov
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