kernel.git/arch/x86, branch linux-3.17.y

x86/tls: Don't validate lm in set_thread_area() after all

2015-01-08T18:27:47Z

commit 3fb2f4237bb452eb4e98f6a5dbd5a445b4fed9d0 upstream. It turns out that there's a lurking ABI issue. GCC, when compiling this in a 32-bit program: struct user_desc desc = { .entry_number = idx, .base_addr = base, .limit = 0xfffff, .seg_32bit = 1, .contents = 0, /* Data, grow-up */ .read_exec_only = 0, .limit_in_pages = 1, .seg_not_present = 0, .useable = 0, }; will leave .lm uninitialized. This means that anything in the kernel that reads user_desc.lm for 32-bit tasks is unreliable. Revert the .lm check in set_thread_area(). The value never did anything in the first place. Fixes: 0e58af4e1d21 ("x86/tls: Disallow unusual TLS segments") Signed-off-by: Andy Lutomirski Acked-by: Thomas Gleixner Cc: Linus Torvalds Link: http://lkml.kernel.org/r/d7875b60e28c512f6a6fc0baf5714d58e7eaadbb.1418856405.git.luto@amacapital.net Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

x86/asm/traps: Disable tracing and kprobes in fixup_bad_iret and sync_regs

2015-01-08T18:27:47Z

commit 7ddc6a2199f1da405a2fb68c40db8899b1a8cd87 upstream. These functions can be executed on the int3 stack, so kprobes are dangerous. Tracing is probably a bad idea, too. Fixes: b645af2d5905 ("x86_64, traps: Rework bad_iret") Signed-off-by: Andy Lutomirski Cc: Linus Torvalds Cc: Steven Rostedt Link: http://lkml.kernel.org/r/50e33d26adca60816f3ba968875801652507d0c4.1416870125.git.luto@amacapital.net Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

x86, kvm: Clear paravirt_enabled on KVM guests for espfix32's benefit

2015-01-08T18:27:44Z

commit 29fa6825463c97e5157284db80107d1bfac5d77b upstream. paravirt_enabled has the following effects: - Disables the F00F bug workaround warning. There is no F00F bug workaround any more because Linux's standard IDT handling already works around the F00F bug, but the warning still exists. This is only cosmetic, and, in any event, there is no such thing as KVM on a CPU with the F00F bug. - Disables 32-bit APM BIOS detection. On a KVM paravirt system, there should be no APM BIOS anyway. - Disables tboot. I think that the tboot code should check the CPUID hypervisor bit directly if it matters. - paravirt_enabled disables espfix32. espfix32 should *not* be disabled under KVM paravirt. The last point is the purpose of this patch. It fixes a leak of the high 16 bits of the kernel stack address on 32-bit KVM paravirt guests. Fixes CVE-2014-8134. Suggested-by: Konrad Rzeszutek Wilk Signed-off-by: Andy Lutomirski Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

x86_64, switch_to(): Load TLS descriptors before switching DS and ES

2015-01-08T18:27:44Z

commit f647d7c155f069c1a068030255c300663516420e upstream. Otherwise, if buggy user code points DS or ES into the TLS array, they would be corrupted after a context switch. This also significantly improves the comments and documents some gotchas in the code. Before this patch, the both tests below failed. With this patch, the es test passes, although the gsbase test still fails. ----- begin es test ----- /* * Copyright (c) 2014 Andy Lutomirski * GPL v2 */ static unsigned short GDT3(int idx) { return (idx << 3) | 3; } static int create_tls(int idx, unsigned int base) { struct user_desc desc = { .entry_number = idx, .base_addr = base, .limit = 0xfffff, .seg_32bit = 1, .contents = 0, /* Data, grow-up */ .read_exec_only = 0, .limit_in_pages = 1, .seg_not_present = 0, .useable = 0, }; if (syscall(SYS_set_thread_area, &desc) != 0) err(1, "set_thread_area"); return desc.entry_number; } int main() { int idx = create_tls(-1, 0); printf("Allocated GDT index %d\n", idx); unsigned short orig_es; asm volatile ("mov %%es,%0" : "=rm" (orig_es)); int errors = 0; int total = 1000; for (int i = 0; i < total; i++) { asm volatile ("mov %0,%%es" : : "rm" (GDT3(idx))); usleep(100); unsigned short es; asm volatile ("mov %%es,%0" : "=rm" (es)); asm volatile ("mov %0,%%es" : : "rm" (orig_es)); if (es != GDT3(idx)) { if (errors == 0) printf("[FAIL]\tES changed from 0x%hx to 0x%hx\n", GDT3(idx), es); errors++; } } if (errors) { printf("[FAIL]\tES was corrupted %d/%d times\n", errors, total); return 1; } else { printf("[OK]\tES was preserved\n"); return 0; } } ----- end es test ----- ----- begin gsbase test ----- /* * gsbase.c, a gsbase test * Copyright (c) 2014 Andy Lutomirski * GPL v2 */ static unsigned char *testptr, *testptr2; static unsigned char read_gs_testvals(void) { unsigned char ret; asm volatile ("movb %%gs:%1, %0" : "=r" (ret) : "m" (*testptr)); return ret; } int main() { int errors = 0; testptr = mmap((void *)0x200000000UL, 1, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS, -1, 0); if (testptr == MAP_FAILED) err(1, "mmap"); testptr2 = mmap((void *)0x300000000UL, 1, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED | MAP_ANONYMOUS, -1, 0); if (testptr2 == MAP_FAILED) err(1, "mmap"); *testptr = 0; *testptr2 = 1; if (syscall(SYS_arch_prctl, ARCH_SET_GS, (unsigned long)testptr2 - (unsigned long)testptr) != 0) err(1, "ARCH_SET_GS"); usleep(100); if (read_gs_testvals() == 1) { printf("[OK]\tARCH_SET_GS worked\n"); } else { printf("[FAIL]\tARCH_SET_GS failed\n"); errors++; } asm volatile ("mov %0,%%gs" : : "r" (0)); if (read_gs_testvals() == 0) { printf("[OK]\tWriting 0 to gs worked\n"); } else { printf("[FAIL]\tWriting 0 to gs failed\n"); errors++; } usleep(100); if (read_gs_testvals() == 0) { printf("[OK]\tgsbase is still zero\n"); } else { printf("[FAIL]\tgsbase was corrupted\n"); errors++; } return errors == 0 ? 0 : 1; } ----- end gsbase test ----- Signed-off-by: Andy Lutomirski Cc: Andi Kleen Cc: Linus Torvalds Link: http://lkml.kernel.org/r/509d27c9fec78217691c3dad91cec87e1006b34a.1418075657.git.luto@amacapital.net Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

x86/tls: Disallow unusual TLS segments

2015-01-08T18:27:44Z

commit 0e58af4e1d2166e9e33375a0f121e4867010d4f8 upstream. Users have no business installing custom code segments into the GDT, and segments that are not present but are otherwise valid are a historical source of interesting attacks. For completeness, block attempts to set the L bit. (Prior to this patch, the L bit would have been silently dropped.) This is an ABI break. I've checked glibc, musl, and Wine, and none of them look like they'll have any trouble. Note to stable maintainers: this is a hardening patch that fixes no known bugs. Given the possibility of ABI issues, this probably shouldn't be backported quickly. Signed-off-by: Andy Lutomirski Acked-by: H. Peter Anvin Cc: Konrad Rzeszutek Wilk Cc: Linus Torvalds Cc: Willy Tarreau Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

x86/tls: Validate TLS entries to protect espfix

2015-01-08T18:27:44Z

commit 41bdc78544b8a93a9c6814b8bbbfef966272abbe upstream. Installing a 16-bit RW data segment into the GDT defeats espfix. AFAICT this will not affect glibc, Wine, or dosemu at all. Signed-off-by: Andy Lutomirski Acked-by: H. Peter Anvin Cc: Konrad Rzeszutek Wilk Cc: Linus Torvalds Cc: Willy Tarreau Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

x86: Use $(OBJDUMP) instead of plain objdump

2014-12-16T17:37:08Z

commit e2e68ae688b0a3766cd75aedf4ed4e39be402009 upstream. commit e6023367d779 'x86, kaslr: Prevent .bss from overlaping initrd' broke the cross compile of x86. It added a objdump invocation, which invokes the host native objdump and ignores an active cross tool chain. Use $(OBJDUMP) instead which takes the CROSS_COMPILE prefix into account. [ tglx: Massage changelog and use $(OBJDUMP) ] Fixes: e6023367d779 'x86, kaslr: Prevent .bss from overlaping initrd' Signed-off-by: Chris Clayton Acked-by: Kees Cook Acked-by: Borislav Petkov Cc: Junjie Mao Cc: Ingo Molnar Cc: H. Peter Anvin Link: http://lkml.kernel.org/r/54705C8E.1080400@googlemail.com Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

x86: kvm: use alternatives for VMCALL vs. VMMCALL if kernel text is read-only

2014-12-06T23:57:34Z

commit c1118b3602c2329671ad5ec8bdf8e374323d6343 upstream. On x86_64, kernel text mappings are mapped read-only with CONFIG_DEBUG_RODATA. In that case, KVM will fail to patch VMCALL instructions to VMMCALL as required on AMD processors. The failure mode is currently a divide-by-zero exception, which obviously is a KVM bug that has to be fixed. However, picking the right instruction between VMCALL and VMMCALL will be faster and will help if you cannot upgrade the hypervisor. Reported-by: Chris Webb Tested-by: Chris Webb Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Acked-by: Borislav Petkov Signed-off-by: Paolo Bonzini Cc: Chris J Arges Signed-off-by: Greg Kroah-Hartman

uprobes, x86: Fix _TIF_UPROBE vs _TIF_NOTIFY_RESUME

2014-12-06T23:57:16Z

commit 82975bc6a6df743b9a01810fb32cb65d0ec5d60b upstream. x86 call do_notify_resume on paranoid returns if TIF_UPROBE is set but not on non-paranoid returns. I suspect that this is a mistake and that the code only works because int3 is paranoid. Setting _TIF_NOTIFY_RESUME in the uprobe code was probably a workaround for the x86 bug. With that bug fixed, we can remove _TIF_NOTIFY_RESUME from the uprobes code. Reported-by: Oleg Nesterov Acked-by: Srikar Dronamraju Acked-by: Borislav Petkov Signed-off-by: Andy Lutomirski Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

x86, kaslr: Handle Gold linker for finding bss/brk

2014-12-06T23:57:15Z

commit 70b61e362187b5fccac206506d402f3424e3e749 upstream. When building with the Gold linker, the .bss and .brk areas of vmlinux are shown as consecutive instead of having the same file offset. Allow for either state, as long as things add up correctly. Fixes: e6023367d779 ("x86, kaslr: Prevent .bss from overlaping initrd") Reported-by: Markus Trippelsdorf Signed-off-by: Kees Cook Cc: Junjie Mao Link: http://lkml.kernel.org/r/20141118001604.GA25045@www.outflux.net Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman