mm: Check if PUD is large when validating a kernel address
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Dave Jones
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477047eeed
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@ -791,6 +791,8 @@ Patch22247: ath9k_rx_dma_stop_check.patch
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Patch23000: silence-brcmsmac-warning.patch
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Patch23100: validate-pud-largepage.patch
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# END OF PATCH DEFINITIONS
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%endif
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@ -1519,6 +1521,8 @@ ApplyPatch ath9k_rx_dma_stop_check.patch
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ApplyPatch silence-brcmsmac-warning.patch
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ApplyPatch validate-pud-largepage.patch
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# END OF PATCH APPLICATIONS
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%endif
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@ -2382,6 +2386,9 @@ fi
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# ||----w |
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# || ||
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%changelog
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* Tue Feb 12 2013 Dave Jones <davej@redhat.com>
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- mm: Check if PUD is large when validating a kernel address
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* Tue Feb 12 2013 Dave Jones <davej@redhat.com>
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- Silence brcmsmac warnings. (Fixed in 3.8, but not backporting to 3.7)
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@ -0,0 +1,102 @@
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Date: Mon, 11 Feb 2013 14:52:36 +0000
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From: Mel Gorman <mgorman@suse.de>
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To: Ingo Molnar <mingo@kernel.org>, Andrew Morton <akpm@linux-foundation.org>
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Cc: Mel Gorman <mgorman@suse.de>, linux-kernel@vger.kernel.org, linux-mm@kvack.org
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Subject: [PATCH] x86: mm: Check if PUD is large when validating a kernel address
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Message-ID: <20130211145236.GX21389@suse.de>
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MIME-Version: 1.0
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A user reported the following oops when a backup process read
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/proc/kcore.
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BUG: unable to handle kernel paging request at ffffbb00ff33b000
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IP: [<ffffffff8103157e>] kern_addr_valid+0xbe/0x110
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PGD 0
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Oops: 0000 [#1] SMP
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CPU 6
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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
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Pid: 16196, comm: Hibackp Not tainted 3.0.13-0.27-default #1 IBM System x3550 M3 -[7944 K3G]-/94Y7614
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RIP: 0010:[<ffffffff8103157e>] [<ffffffff8103157e>] kern_addr_valid+0xbe/0x110
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RSP: 0018:ffff88094165fe80 EFLAGS: 00010246
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RAX: 00003300ff33b000 RBX: ffff880100000000 RCX: 0000000000000000
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RDX: 0000000100000000 RSI: ffff880000000000 RDI: ff32b300ff33b400
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RBP: 0000000000001000 R08: 00003ffffffff000 R09: 0000000000000000
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R10: 22302e31223d6e6f R11: 0000000000000246 R12: 0000000000001000
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R13: 0000000000003000 R14: 0000000000571be0 R15: ffff88094165ff50
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FS: 00007ff152d33700(0000) GS:ffff88097f2c0000(0000) knlGS:0000000000000000
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CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
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CR2: ffffbb00ff33b000 CR3: 00000009405a3000 CR4: 00000000000006e0
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DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
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DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
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Process Hibackp (pid: 16196, threadinfo ffff88094165e000, task ffff8808eb9ba600)
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Stack:
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ffffffff811b8aaa 0000000000004000 ffff880943fea480 ffff8808ef2bae50
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ffff880943d32980 fffffffffffffffb ffff8808ef2bae40 ffff88094165ff50
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0000000000004000 000000000056ebe0 ffffffff811ad847 000000000056ebe0
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Call Trace:
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[<ffffffff811b8aaa>] read_kcore+0x17a/0x370
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[<ffffffff811ad847>] proc_reg_read+0x77/0xc0
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[<ffffffff81151687>] vfs_read+0xc7/0x130
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[<ffffffff811517f3>] sys_read+0x53/0xa0
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[<ffffffff81449692>] system_call_fastpath+0x16/0x1b
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Investigation determined that the bug triggered when reading system RAM
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at the 4G mark. On this system, that was the first address using 1G pages
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for the virt->phys direct mapping so the PUD is pointing to a physical
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address, not a PMD page. The problem is that the page table walker in
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kern_addr_valid() is not checking pud_large() and treats the physical
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address as if it was a PMD. If it happens to look like pmd_none then it'll
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silently fail, probably returning zeros instead of real data. If the data
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happens to look like a present PMD though, it will be walked resulting in
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the oops above. This patch adds the necessary pud_large() check.
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Unfortunately the problem was not readily reproducible and now they are
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running the backup program without accessing /proc/kcore so the patch has
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not been validated but I think it makes sense. If reviewers agree then it
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should also be included in -stable back as far as 3.0-stable.
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Cc: stable@vger.kernel.org
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Signed-off-by: Mel Gorman <mgorman@suse.de>
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---
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arch/x86/include/asm/pgtable.h | 5 +++++
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arch/x86/mm/init_64.c | 3 +++
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2 files changed, 8 insertions(+)
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diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
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index 5199db2..1c1a955 100644
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--- a/arch/x86/include/asm/pgtable.h
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+++ b/arch/x86/include/asm/pgtable.h
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@@ -142,6 +142,11 @@ static inline unsigned long pmd_pfn(pmd_t pmd)
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return (pmd_val(pmd) & PTE_PFN_MASK) >> PAGE_SHIFT;
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}
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+static inline unsigned long pud_pfn(pud_t pud)
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+{
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+ return (pud_val(pud) & PTE_PFN_MASK) >> PAGE_SHIFT;
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+}
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+
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#define pte_page(pte) pfn_to_page(pte_pfn(pte))
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static inline int pmd_large(pmd_t pte)
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diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
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index 2ead3c8..75c9a6a 100644
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--- a/arch/x86/mm/init_64.c
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+++ b/arch/x86/mm/init_64.c
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@@ -831,6 +831,9 @@ int kern_addr_valid(unsigned long addr)
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if (pud_none(*pud))
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return 0;
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+ if (pud_large(*pud))
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+ return pfn_valid(pud_pfn(*pud));
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+
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pmd = pmd_offset(pud, addr);
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if (pmd_none(*pmd))
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return 0;
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--
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