From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id B6AABB6F64 for ; Fri, 2 Dec 2011 12:25:38 +1100 (EST) Message-ID: <1322789008.3729.42.camel@pasglop> Subject: Re: [PATCH][v2] Enable CONFIG_STRICT_DEVMEM support for Powerpc From: Benjamin Herrenschmidt To: Sukadev Bhattiprolu Date: Fri, 02 Dec 2011 12:23:28 +1100 In-Reply-To: <20111202001141.GA14860@us.ibm.com> References: <20111202001141.GA14860@us.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, sbest@us.ibm.com, paulus@samba.org, anton@samba.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 2011-12-01 at 16:11 -0800, Sukadev Bhattiprolu wrote: > >From aebed2e9fb9fba7dd0a34595780b828d7a545ba2 Mon Sep 17 00:00:00 2001 > From: Sukadev Bhattiprolu > Date: Mon, 29 Aug 2011 14:12:08 -0700 > Subject: [PATCH 1/1][v2] Enable CONFIG_STRICT_DEVMEM support for Powerpc. > > As described in the help text in the patch, this token restricts general > access to /dev/mem as a way of increasing security. Specifically, access > to exclusive IOMEM and kernel RAM is denied unless CONFIG_STRICT_DEVMEM is > set to 'n'. > > Implement the 'devmem_is_allowed()' interface for POWER. It will be > called from range_is_allowed() when userpsace attempts to access /dev/mem. > > This patch is based on an earlier patch from Steve Best and with input from > Paul Mackerras. A slightly different version of that patch is already in my -next branch since earlier this week. Please send a followup patch adding the missing rtas bit. Note that I've dropped the generic printk change which has nothing to do in that patch and can/should be submitted separately if it's really needed. Cheers, Ben. > A test for this patch: > > # cat /proc/rtas/rmo_buffer > 000000000f190000 10000 > > # python -c "print 0x000000000f190000 / 0x10000" > 3865 > > # dd if=/dev/mem of=/tmp/foo count=1 bs=64k skip=3865 > 1+0 records in > 1+0 records out > 65536 bytes (66 kB) copied, 0.000205235 s, 319 MB/s > > # dd if=/dev/mem of=/tmp/foo count=1 bs=64k skip=3864 > dd: reading `/dev/mem': Operation not permitted > 0+0 records in > 0+0 records out > 0 bytes (0 B) copied, 0.000226844 s, 0.0 kB/s > > # dd if=/dev/mem of=/tmp/foo count=1 bs=64k skip=3866 > dd: reading `/dev/mem': Operation not permitted > 0+0 records in > 0+0 records out > 0 bytes (0 B) copied, 0.00023542 s, 0.0 kB/s > > # dd if=/dev/mem of=/tmp/foo > dd: reading `/dev/mem': Operation not permitted > 0+0 records in > 0+0 records out > 0 bytes (0 B) copied, 0.00022519 s, 0.0 kB/s > > Changelog[v2]: > - [Anton Blanchard] Punch a hole in devmem to allow librtas/dlpar > tools access to /dev/mem. > > Signed-off-by: Sukadev Bhattiprolu > --- > arch/powerpc/Kconfig.debug | 12 ++++++++++++ > arch/powerpc/include/asm/page.h | 1 + > arch/powerpc/kernel/rtas.c | 10 ++++++++++ > arch/powerpc/mm/mem.c | 20 ++++++++++++++++++++ > drivers/char/mem.c | 5 +++-- > 5 files changed, 46 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug > index 067cb84..1cf1b00 100644 > --- a/arch/powerpc/Kconfig.debug > +++ b/arch/powerpc/Kconfig.debug > @@ -298,4 +298,16 @@ config PPC_EARLY_DEBUG_CPM_ADDR > platform probing is done, all platforms selected must > share the same address. > > +config STRICT_DEVMEM > + def_bool y > + prompt "Filter access to /dev/mem" > + help > + This option restricts access to /dev/mem. If this option is > + disabled, you allow userspace access to all memory, including > + kernel and userspace memory. Accidental memory access is likely > + to be disastrous. > + Memory access is required for experts who want to debug the kernel. > + > + If you are unsure, say Y. > + > endmenu > diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h > index 2cd664e..dc2ec96 100644 > --- a/arch/powerpc/include/asm/page.h > +++ b/arch/powerpc/include/asm/page.h > @@ -261,6 +261,7 @@ extern void clear_user_page(void *page, unsigned long vaddr, struct page *pg); > extern void copy_user_page(void *to, void *from, unsigned long vaddr, > struct page *p); > extern int page_is_ram(unsigned long pfn); > +extern int devmem_is_allowed(unsigned long pfn); > > #ifdef CONFIG_PPC_SMLPAR > void arch_free_page(struct page *page, int order); > diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c > index d5ca823..07cf2cf 100644 > --- a/arch/powerpc/kernel/rtas.c > +++ b/arch/powerpc/kernel/rtas.c > @@ -937,6 +937,16 @@ asmlinkage int ppc_rtas(struct rtas_args __user *uargs) > return 0; > } > > +int page_is_rtas(unsigned long pfn) > +{ > + unsigned long paddr = (pfn << PAGE_SHIFT); > + > + if (paddr >= rtas_rmo_buf && paddr < (rtas_rmo_buf + RTAS_RMOBUF_MAX)) > + return 1; > + > + return 0; > +} > + > /* > * Call early during boot, before mem init or bootmem, to retrieve the RTAS > * informations from the device-tree and allocate the RMO buffer for userland > diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c > index c781bbc..d21dbc6 100644 > --- a/arch/powerpc/mm/mem.c > +++ b/arch/powerpc/mm/mem.c > @@ -549,3 +549,23 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, > hash_preload(vma->vm_mm, address, access, trap); > #endif /* CONFIG_PPC_STD_MMU */ > } > + > +extern int page_is_rtas(unsigned long pfn); > + > +/* > + * devmem_is_allowed(): check to see if /dev/mem access to a certain address > + * is valid. The argument is a physical page number. > + * > + * Access has to be given to non-kernel-ram areas as well, these contain the > + * PCI mmio resources as well as potential bios/acpi data regions. > + */ > +int devmem_is_allowed(unsigned long pfn) > +{ > + if (iomem_is_exclusive(pfn << PAGE_SHIFT)) > + return 0; > + if (!page_is_ram(pfn)) > + return 1; > + if (page_is_rtas(pfn)) > + return 1; > + return 0; > +} > diff --git a/drivers/char/mem.c b/drivers/char/mem.c > index 8fc04b4..64917e8 100644 > --- a/drivers/char/mem.c > +++ b/drivers/char/mem.c > @@ -29,6 +29,7 @@ > > #include > #include > +#include > > #ifdef CONFIG_IA64 > # include > @@ -66,8 +67,8 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size) > while (cursor < to) { > if (!devmem_is_allowed(pfn)) { > printk(KERN_INFO > - "Program %s tried to access /dev/mem between %Lx->%Lx.\n", > - current->comm, from, to); > + "Program %s tried to access /dev/mem between %Lx->%Lx and " > + "pfn %lu.\n", current->comm, from, to, pfn); > return 0; > } > cursor += PAGE_SIZE;