kernel.git/arch/x86, branch linux-4.12.y

x86/switch_to/64: Rewrite FS/GS switching yet again to fix AMD CPUs

2017-09-20T06:22:11Z

commit e137a4d8f4dd2e277e355495b6b2cb241a8693c3 upstream. Switching FS and GS is a mess, and the current code is still subtly wrong: it assumes that "Loading a nonzero value into FS sets the index and base", which is false on AMD CPUs if the value being loaded is 1, 2, or 3. (The current code came from commit 3e2b68d752c9 ("x86/asm, sched/x86: Rewrite the FS and GS context switch code"), which made it better but didn't fully fix it.) Rewrite it to be much simpler and more obviously correct. This should fix it fully on AMD CPUs and shouldn't adversely affect performance. Signed-off-by: Andy Lutomirski Cc: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Chang Seok Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

x86/fsgsbase/64: Report FSBASE and GSBASE correctly in core dumps

2017-09-20T06:22:11Z

commit 9584d98bed7a7a904d0702ad06bbcc94703cb5b4 upstream. In ELF_COPY_CORE_REGS, we're copying from the current task, so accessing thread.fsbase and thread.gsbase makes no sense. Just read the values from the CPU registers. In practice, the old code would have been correct most of the time simply because thread.fsbase and thread.gsbase usually matched the CPU registers. Signed-off-by: Andy Lutomirski Cc: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Chang Seok Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

x86/fsgsbase/64: Fully initialize FS and GS state in start_thread_common

2017-09-20T06:22:11Z

commit 767d035d838f4fd6b5a5bbd7a3f6d293b7f65a49 upstream. execve used to leak FSBASE and GSBASE on AMD CPUs. Fix it. The security impact of this bug is small but not quite zero -- it could weaken ASLR when a privileged task execs a less privileged program, but only if program changed bitness across the exec, or the child binary was highly unusual or actively malicious. A child program that was compromised after the exec would not have access to the leaked base. Signed-off-by: Andy Lutomirski Cc: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Chang Seok Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

KVM: SVM: Limit PFERR_NESTED_GUEST_PAGE error_code check to L1 guest

2017-09-13T21:17:30Z

commit 64531a3b70b17c8d3e77f2e49e5e1bb70f571266 upstream. Commit 147277540bbc ("kvm: svm: Add support for additional SVM NPF error codes", 2016-11-23) added a new error code to aid nested page fault handling. The commit unprotects (kvm_mmu_unprotect_page) the page when we get a NPF due to guest page table walk where the page was marked RO. However, if an L0->L2 shadow nested page table can also be marked read-only when a page is read only in L1's nested page table. If such a page is accessed by L2 while walking page tables it can cause a nested page fault (page table walks are write accesses). However, after kvm_mmu_unprotect_page we may get another page fault, and again in an endless stream. To cover this use case, we qualify the new error_code check with vcpu->arch.mmu_direct_map so that the error_code check would run on L1 guest, and not the L2 guest. This avoids hitting the above scenario. Fixes: 147277540bbc54119172481c8ef6d930cc9fbfc2 Cc: Paolo Bonzini Cc: Radim Krčmář Cc: Thomas Lendacky Signed-off-by: Brijesh Singh Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

x86/io: Add "memory" clobber to insb/insw/insl/outsb/outsw/outsl

2017-09-07T06:37:14Z

commit 7206f9bf108eb9513d170c73f151367a1bdf3dbf upstream. The x86 version of insb/insw/insl uses an inline assembly that does not have the target buffer listed as an output. This can confuse the compiler, leading it to think that a subsequent access of the buffer is uninitialized: drivers/net/wireless/wl3501_cs.c: In function ‘wl3501_mgmt_scan_confirm’: drivers/net/wireless/wl3501_cs.c:665:9: error: ‘sig.status’ is used uninitialized in this function [-Werror=uninitialized] drivers/net/wireless/wl3501_cs.c:668:12: error: ‘sig.cap_info’ may be used uninitialized in this function [-Werror=maybe-uninitialized] drivers/net/sb1000.c: In function 'sb1000_rx': drivers/net/sb1000.c:775:9: error: 'st[0]' is used uninitialized in this function [-Werror=uninitialized] drivers/net/sb1000.c:776:10: error: 'st[1]' may be used uninitialized in this function [-Werror=maybe-uninitialized] drivers/net/sb1000.c:784:11: error: 'st[1]' may be used uninitialized in this function [-Werror=maybe-uninitialized] I tried to mark the exact input buffer as an output here, but couldn't figure it out. As suggested by Linus, marking all memory as clobbered however is good enough too. For the outs operations, I also add the memory clobber, to force the input to be written to local variables. This is probably already guaranteed by the "asm volatile", but it can't hurt to do this for symmetry. Suggested-by: Linus Torvalds Signed-off-by: Arnd Bergmann Acked-by: Linus Torvalds Cc: Borislav Petkov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Tom Lendacky Link: http://lkml.kernel.org/r/20170719125310.2487451-5-arnd@arndb.de Link: https://lkml.org/lkml/2017/7/12/605 Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

x86/mm: Fix use-after-free of ldt_struct

2017-08-30T08:26:40Z

commit ccd5b3235180eef3cfec337df1c8554ab151b5cc upstream. The following commit: 39a0526fb3f7 ("x86/mm: Factor out LDT init from context init") renamed init_new_context() to init_new_context_ldt() and added a new init_new_context() which calls init_new_context_ldt(). However, the error code of init_new_context_ldt() was ignored. Consequently, if a memory allocation in alloc_ldt_struct() failed during a fork(), the ->context.ldt of the new task remained the same as that of the old task (due to the memcpy() in dup_mm()). ldt_struct's are not intended to be shared, so a use-after-free occurred after one task exited. Fix the bug by making init_new_context() pass through the error code of init_new_context_ldt(). This bug was found by syzkaller, which encountered the following splat: BUG: KASAN: use-after-free in free_ldt_struct.part.2+0x10a/0x150 arch/x86/kernel/ldt.c:116 Read of size 4 at addr ffff88006d2cb7c8 by task kworker/u9:0/3710 CPU: 1 PID: 3710 Comm: kworker/u9:0 Not tainted 4.13.0-rc4-next-20170811 #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:52 print_address_description+0x73/0x250 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report+0x24e/0x340 mm/kasan/report.c:409 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429 free_ldt_struct.part.2+0x10a/0x150 arch/x86/kernel/ldt.c:116 free_ldt_struct arch/x86/kernel/ldt.c:173 [inline] destroy_context_ldt+0x60/0x80 arch/x86/kernel/ldt.c:171 destroy_context arch/x86/include/asm/mmu_context.h:157 [inline] __mmdrop+0xe9/0x530 kernel/fork.c:889 mmdrop include/linux/sched/mm.h:42 [inline] exec_mmap fs/exec.c:1061 [inline] flush_old_exec+0x173c/0x1ff0 fs/exec.c:1291 load_elf_binary+0x81f/0x4ba0 fs/binfmt_elf.c:855 search_binary_handler+0x142/0x6b0 fs/exec.c:1652 exec_binprm fs/exec.c:1694 [inline] do_execveat_common.isra.33+0x1746/0x22e0 fs/exec.c:1816 do_execve+0x31/0x40 fs/exec.c:1860 call_usermodehelper_exec_async+0x457/0x8f0 kernel/umh.c:100 ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431 Allocated by task 3700: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551 kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3627 kmalloc include/linux/slab.h:493 [inline] alloc_ldt_struct+0x52/0x140 arch/x86/kernel/ldt.c:67 write_ldt+0x7b7/0xab0 arch/x86/kernel/ldt.c:277 sys_modify_ldt+0x1ef/0x240 arch/x86/kernel/ldt.c:307 entry_SYSCALL_64_fastpath+0x1f/0xbe Freed by task 3700: save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59 save_stack+0x43/0xd0 mm/kasan/kasan.c:447 set_track mm/kasan/kasan.c:459 [inline] kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524 __cache_free mm/slab.c:3503 [inline] kfree+0xca/0x250 mm/slab.c:3820 free_ldt_struct.part.2+0xdd/0x150 arch/x86/kernel/ldt.c:121 free_ldt_struct arch/x86/kernel/ldt.c:173 [inline] destroy_context_ldt+0x60/0x80 arch/x86/kernel/ldt.c:171 destroy_context arch/x86/include/asm/mmu_context.h:157 [inline] __mmdrop+0xe9/0x530 kernel/fork.c:889 mmdrop include/linux/sched/mm.h:42 [inline] __mmput kernel/fork.c:916 [inline] mmput+0x541/0x6e0 kernel/fork.c:927 copy_process.part.36+0x22e1/0x4af0 kernel/fork.c:1931 copy_process kernel/fork.c:1546 [inline] _do_fork+0x1ef/0xfb0 kernel/fork.c:2025 SYSC_clone kernel/fork.c:2135 [inline] SyS_clone+0x37/0x50 kernel/fork.c:2129 do_syscall_64+0x26c/0x8c0 arch/x86/entry/common.c:287 return_from_SYSCALL_64+0x0/0x7a Here is a C reproducer: #include #include #include #include #include #include #include static void *fork_thread(void *_arg) { fork(); } int main(void) { struct user_desc desc = { .entry_number = 8191 }; syscall(__NR_modify_ldt, 1, &desc, sizeof(desc)); for (;;) { if (fork() == 0) { pthread_t t; srand(getpid()); pthread_create(&t, NULL, fork_thread, NULL); usleep(rand() % 10000); syscall(__NR_exit_group, 0); } wait(NULL); } } Note: the reproducer takes advantage of the fact that alloc_ldt_struct() may use vmalloc() to allocate a large ->entries array, and after commit: 5d17a73a2ebe ("vmalloc: back off when the current task is killed") it is possible for userspace to fail a task's vmalloc() by sending a fatal signal, e.g. via exit_group(). It would be more difficult to reproduce this bug on kernels without that commit. This bug only affected kernels with CONFIG_MODIFY_LDT_SYSCALL=y. Signed-off-by: Eric Biggers Acked-by: Dave Hansen Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Christoph Hellwig Cc: Denys Vlasenko Cc: Dmitry Vyukov Cc: Linus Torvalds Cc: Michal Hocko Cc: Peter Zijlstra Cc: Rik van Riel Cc: Tetsuo Handa Cc: Thomas Gleixner Cc: linux-mm@kvack.org Fixes: 39a0526fb3f7 ("x86/mm: Factor out LDT init from context init") Link: http://lkml.kernel.org/r/20170824175029.76040-1-ebiggers3@gmail.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

KVM: x86: block guest protection keys unless the host has them enabled

2017-08-30T08:26:30Z

commit c469268cd523245cc58255f6696e0c295485cb0b upstream. If the host has protection keys disabled, we cannot read and write the guest PKRU---RDPKRU and WRPKRU fail with #GP(0) if CR4.PKE=0. Block the PKU cpuid bit in that case. This ensures that guest_CR4.PKE=1 implies host_CR4.PKE=1. Fixes: 1be0e61c1f255faaeab04a390e00c8b9b9042870 Reviewed-by: David Hildenbrand Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

KVM, pkeys: do not use PKRU value in vcpu->arch.guest_fpu.state

2017-08-30T08:26:30Z

commit 38cfd5e3df9c4f88e76b547eee2087ee5c042ae2 upstream. The host pkru is restored right after vcpu exit (commit 1be0e61), so KVM_GET_XSAVE will return the host PKRU value instead. Fix this by using the guest PKRU explicitly in fill_xsave and load_xsave. This part is based on a patch by Junkang Fu. The host PKRU data may also not match the value in vcpu->arch.guest_fpu.state, because it could have been changed by userspace since the last time it was saved, so skip loading it in kvm_load_guest_fpu. Reported-by: Junkang Fu Cc: Yang Zhang Fixes: 1be0e61c1f255faaeab04a390e00c8b9b9042870 Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

KVM: x86: simplify handling of PKRU

2017-08-30T08:26:30Z

commit b9dd21e104bcd45e124acfe978a79df71259e59b upstream. Move it to struct kvm_arch_vcpu, replacing guest_pkru_valid with a simple comparison against the host value of the register. The write of PKRU in addition can be skipped if the guest has not enabled the feature. Once we do this, we need not test OSPKE in the host anymore, because guest_CR4.PKE=1 implies host_CR4.PKE=1. The static PKU test is kept to elide the code on older CPUs. Suggested-by: Yang Zhang Fixes: 1be0e61c1f255faaeab04a390e00c8b9b9042870 Reviewed-by: David Hildenbrand Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman

debug: Fix WARN_ON_ONCE() for modules

2017-08-25T00:15:05Z

commit 325cdacd03c12629aa5f9ee2ace49b1f3dc184a8 upstream. Mike Galbraith reported a situation where a WARN_ON_ONCE() call in DRM code turned into an oops. As it turns out, WARN_ON_ONCE() seems to be completely broken when called from a module. The bug was introduced with the following commit: 19d436268dde ("debug: Add _ONCE() logic to report_bug()") That commit changed WARN_ON_ONCE() to move its 'once' logic into the bug trap handler. It requires a writable bug table so that the BUGFLAG_DONE bit can be written to the flags to indicate the first warning has occurred. The bug table was made writable for vmlinux, which relies on vmlinux.lds.S and vmlinux.lds.h for laying out the sections. However, it wasn't made writable for modules, which rely on the ELF section header flags. Reported-by: Mike Galbraith Tested-by: Masami Hiramatsu Signed-off-by: Josh Poimboeuf Acked-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 19d436268dde ("debug: Add _ONCE() logic to report_bug()") Link: http://lkml.kernel.org/r/a53b04235a65478dd9afc51f5b329fdc65c84364.1500095401.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar Signed-off-by: Changbin Du Signed-off-by: Greg Kroah-Hartman