Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752188Ab3CAGoF (ORCPT ); Fri, 1 Mar 2013 01:44:05 -0500 Received: from mail-pb0-f52.google.com ([209.85.160.52]:51362 "EHLO mail-pb0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751988Ab3CAGoD (ORCPT ); Fri, 1 Mar 2013 01:44:03 -0500 Message-ID: <51304E29.40900@gmail.com> Date: Fri, 01 Mar 2013 14:43:53 +0800 From: Simon Jeons User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130221 Thunderbird/17.0.3 MIME-Version: 1.0 To: Mel Gorman CC: Ingo Molnar , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, riel@redhat.com, mhocko@suse.cz, hannes@cmpxchg.org Subject: Re: [PATCH] x86: mm: Check if PUD is large when validating a kernel address v2 References: <20130211145236.GX21389@suse.de> <20130213110202.GI4100@suse.de> In-Reply-To: <20130213110202.GI4100@suse.de> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5057 Lines: 106 On 02/13/2013 07:02 PM, Mel Gorman wrote: > Andrew or Ingo, please pick up. > > Changelog since v1 > o Add reviewed-bys and acked-bys > > A user reported a bug whereby a backup process accessing /proc/kcore > caused an oops. > > BUG: unable to handle kernel paging request at ffffbb00ff33b000 > IP: [] kern_addr_valid+0xbe/0x110 > PGD 0 > Oops: 0000 [#1] SMP > CPU 6 > Modules linked in: af_packet nfs lockd fscache auth_rpcgss nfs_acl sunrpc 8021q garp stp llc cpufreq_conservative cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf microcode fuse nls_iso8859_1 nls_cp437 vfat fat loop dm_mod ioatdma ipv6 ipv6_lib igb dca i7core_edac edac_core i2c_i801 i2c_core cdc_ether usbnet bnx2 mii iTCO_wdt iTCO_vendor_support shpchp rtc_cmos pci_hotplug tpm_tis sg tpm pcspkr tpm_bios serio_raw button ext3 jbd mbcache uhci_hcd ehci_hcd usbcore sd_mod crc_t10dif usb_common processor thermal_sys hwmon scsi_dh_emc scsi_dh_rdac scsi_dh_alua scsi_dh_hp_sw scsi_dh ata_generic ata_piix libata megaraid_sas scsi_mod > > Pid: 16196, comm: Hibackp Not tainted 3.0.13-0.27-default #1 IBM System x3550 M3 -[7944 K3G]-/94Y7614 > RIP: 0010:[] [] kern_addr_valid+0xbe/0x110 > RSP: 0018:ffff88094165fe80 EFLAGS: 00010246 > RAX: 00003300ff33b000 RBX: ffff880100000000 RCX: 0000000000000000 > RDX: 0000000100000000 RSI: ffff880000000000 RDI: ff32b300ff33b400 > RBP: 0000000000001000 R08: 00003ffffffff000 R09: 0000000000000000 > R10: 22302e31223d6e6f R11: 0000000000000246 R12: 0000000000001000 > R13: 0000000000003000 R14: 0000000000571be0 R15: ffff88094165ff50 > FS: 00007ff152d33700(0000) GS:ffff88097f2c0000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > CR2: ffffbb00ff33b000 CR3: 00000009405a3000 CR4: 00000000000006e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > Process Hibackp (pid: 16196, threadinfo ffff88094165e000, task ffff8808eb9ba600) > Stack: > ffffffff811b8aaa 0000000000004000 ffff880943fea480 ffff8808ef2bae50 > ffff880943d32980 fffffffffffffffb ffff8808ef2bae40 ffff88094165ff50 > 0000000000004000 000000000056ebe0 ffffffff811ad847 000000000056ebe0 > Call Trace: > [] read_kcore+0x17a/0x370 > [] proc_reg_read+0x77/0xc0 > [] vfs_read+0xc7/0x130 > [] sys_read+0x53/0xa0 > [] system_call_fastpath+0x16/0x1b > > Investigation determined that the bug triggered when reading system RAM > at the 4G mark. On this system, that was the first address using 1G pages Do you mean there is one page which is 1G? > for the virt->phys direct mapping so the PUD is pointing to a physical > address, not a PMD page. The problem is that the page table walker in > kern_addr_valid() is not checking pud_large() and treats the physical > address as if it was a PMD. If it happens to look like pmd_none then it'll > silently fail, probably returning zeros instead of real data. If the data > happens to look like a present PMD though, it will be walked resulting in > the oops above. This patch adds the necessary pud_large() check. > > Cc: stable@vger.kernel.org > Signed-off-by: Mel Gorman > Reviewed-by: Rik van Riel > Reviewed-by: Michal Hocko > Acked-by: Johannes Weiner > --- > arch/x86/include/asm/pgtable.h | 5 +++++ > arch/x86/mm/init_64.c | 3 +++ > 2 files changed, 8 insertions(+) > > diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h > index 5199db2..1c1a955 100644 > --- a/arch/x86/include/asm/pgtable.h > +++ b/arch/x86/include/asm/pgtable.h > @@ -142,6 +142,11 @@ static inline unsigned long pmd_pfn(pmd_t pmd) > return (pmd_val(pmd) & PTE_PFN_MASK) >> PAGE_SHIFT; > } > > +static inline unsigned long pud_pfn(pud_t pud) > +{ > + return (pud_val(pud) & PTE_PFN_MASK) >> PAGE_SHIFT; > +} > + > #define pte_page(pte) pfn_to_page(pte_pfn(pte)) > > static inline int pmd_large(pmd_t pte) > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c > index 2ead3c8..75c9a6a 100644 > --- a/arch/x86/mm/init_64.c > +++ b/arch/x86/mm/init_64.c > @@ -831,6 +831,9 @@ int kern_addr_valid(unsigned long addr) > if (pud_none(*pud)) > return 0; > > + if (pud_large(*pud)) > + return pfn_valid(pud_pfn(*pud)); > + > pmd = pmd_offset(pud, addr); > if (pmd_none(*pmd)) > return 0; > > -- > 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: email@kvack.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/