From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx165.postini.com [74.125.245.165]) by kanga.kvack.org (Postfix) with SMTP id 19A246B0005 for ; Wed, 13 Feb 2013 06:02:09 -0500 (EST) Date: Wed, 13 Feb 2013 11:02:02 +0000 From: Mel Gorman Subject: [PATCH] x86: mm: Check if PUD is large when validating a kernel address v2 Message-ID: <20130213110202.GI4100@suse.de> References: <20130211145236.GX21389@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20130211145236.GX21389@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar , Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, riel@redhat.com, mhocko@suse.cz, hannes@cmpxchg.org 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 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