lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 29 Aug 2014 09:04:41 -0700 From: Kees Cook <keescook@...omium.org> To: Will Deacon <will.deacon@....com> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Rob Herring <robh@...nel.org>, Laura Abbott <lauraa@...eaurora.org>, Leif Lindholm <leif.lindholm@...aro.org>, Stephen Boyd <sboyd@...eaurora.org>, "msalter@...hat.com" <msalter@...hat.com>, Rabin Vincent <rabin@....in>, Liu hua <sdu.liu@...wei.com>, Nikolay Borisov <Nikolay.Borisov@....com>, Nicolas Pitre <nicolas.pitre@...aro.org>, Tomasz Figa <t.figa@...sung.com>, Doug Anderson <dianders@...gle.com>, Jason Wessel <jason.wessel@...driver.com>, Catalin Marinas <Catalin.Marinas@....com>, Russell King - ARM Linux <linux@....linux.org.uk>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org> Subject: Re: [PATCH v4 7/8] ARM: mm: allow non-text sections to be non-executable On Tue, Aug 26, 2014 at 7:43 AM, Will Deacon <will.deacon@....com> wrote: > On Wed, Aug 20, 2014 at 01:37:14PM +0100, Kees Cook wrote: >> On Tue, Aug 19, 2014 at 7:33 AM, Will Deacon <will.deacon@....com> wrote: >> > On Wed, Aug 13, 2014 at 06:06:32PM +0100, Kees Cook wrote: >> >> +/* >> >> + * Updates section permissions only for the current mm (sections are >> >> + * copied into each mm). During startup, this is the init_mm. >> >> + */ >> >> +static inline void section_update(unsigned long addr, pmdval_t mask, >> >> + pmdval_t prot) >> >> +{ >> >> + struct mm_struct *mm; >> >> + pmd_t *pmd; >> >> + >> >> + mm = current->active_mm; >> >> + pmd = pmd_offset(pud_offset(pgd_offset(mm, addr), addr), addr); >> >> + >> >> +#ifdef CONFIG_ARM_LPAE >> >> + pmd[0] = __pmd((pmd_val(pmd[0]) & mask) | prot); >> >> +#else >> >> + if (addr & SECTION_SIZE) >> >> + pmd[1] = __pmd((pmd_val(pmd[1]) & mask) | prot); >> >> + else >> >> + pmd[0] = __pmd((pmd_val(pmd[0]) & mask) | prot); >> >> +#endif >> >> + flush_pmd_entry(pmd); >> >> + local_flush_tlb_kernel_range(addr, addr + SECTION_SIZE); >> > >> > Why only a local flush? You're changing global mappings here, right? >> >> Yes, but with the a15 errata, it cannot use a global flush. As a >> result, section_update can only be used by a single CPU which is how >> the usage is managed. Perhaps I should add some comments to that >> effect? (There was a thread a few months ago on this problem and this >> shook out as a solution.) > > Hmm, so do you mandate that preemption is disabled during sections of code > where the permissions must be changed after boot? (e.g. ftrace patching) I guess it's not enforced (how do I make sure preempt is off?), but it's only used during the ftrace patching. I'm open to suggestions! (I had avoided going the fixmap route since I would have expected that to be much slower.) -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists