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The STR and SLDT instructions are not valid when running on virtual-8086
mode and generate an invalid operand exception. These two instructions are
protected by the Intel User-Mode Instruction Prevention (UMIP) security
feature. In protected mode, if UMIP is enabled, these instructions generate
a general protection fault if called from CPL > 0. Linux traps the general
protection fault and emulates the instructions sgdt, sidt and smsw; but not
str and sldt.
These tests are added to verify that the emulation code does not emulate
these two instructions but the expected invalid operand exception is
seen.
Tests fallback to exit with INT3 in case emulation does happen.
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: ricardo.neri@intel.com
Link: http://lkml.kernel.org/r/1509935277-22138-13-git-send-email-ricardo.neri-calderon@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Certain user space programs that run on virtual-8086 mode may utilize
instructions protected by the User-Mode Instruction Prevention (UMIP)
security feature present in new Intel processors: SGDT, SIDT and SMSW. In
such a case, a general protection fault is issued if UMIP is enabled. When
such a fault happens, the kernel traps it and emulates the results of
these instructions with dummy values. The purpose of this new
test is to verify whether the impacted instructions can be executed
without causing such #GP. If no #GP exceptions occur, we expect to exit
virtual-8086 mode from INT3.
The instructions protected by UMIP are executed in representative use
cases:
a) displacement-only memory addressing
b) register-indirect memory addressing
c) results stored directly in operands
Unfortunately, it is not possible to check the results against a set of
expected values because no emulation will occur in systems that do not
have the UMIP feature. Instead, results are printed for verification. A
simple verification is done to ensure that results of all tests are
identical.
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: ricardo.neri@intel.com
Link: http://lkml.kernel.org/r/1509935277-22138-12-git-send-email-ricardo.neri-calderon@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Mere possession of vm86 state is strange. Make sure that nothing
gets corrupted if we fork after calling vm86().
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Stas Sergeev <stsp@list.ru>
Link: http://lkml.kernel.org/r/08f83295460a80e41dc5e3e81ec40d6844d316f5.1446270067.git.luto@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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vm86 exposes an interesting attack surface against the entry
code. Since vm86 is mostly useless anyway if mmap_min_addr != 0,
just turn it off in that case.
There are some reports that vbetool can work despite setting
mmap_min_addr to zero. This shouldn't break that use case,
as CAP_SYS_RAWIO already overrides mmap_min_addr.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Austin S Hemmelgarn <ahferroin7@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Josh Boyer <jwboyer@fedoraproject.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stas Sergeev <stsp@list.ru>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The test failed due to an oversight on my part when run on a
64-bit kernel. vm86 isn't expected to work at all, and I
mistakenly failed one part of the test because no signal was
delivered.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/502c8bef877b33fe4943885ded6125dfcc7892db.1438205722.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The entry_from_vm86 selftest was very weak. Improve it: test
more types of kernel entries from vm86 mode and test them more
carefully.
While we're at it, try to improve behavior on non-SEP CPUs. The
old code was buggy because I misunderstood the intended
semantics of #UD in vm86, so I didn't handle a possible signal.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/d8ef1d7368ac70d8342481563ed50f9a7d2eea6f.1436492057.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Test a couple of special cases in 32-bit kernels for entries
from vm86 mode. This will OOPS both old kernels due to a bug
and and 4.1-rc5 due to a regression I introduced, and it should
make sure that the SYSENTER-from-vm86-mode hack in the kernel
keeps working.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/09a9916761e0a9e42d4922f147af45a0079cc1e8.1432936374.git.luto@kernel.org
Tests: 394838c96013 x86/asm/entry/32: Fix user_mode() misuses
Tests: 7ba554b5ac69 x86/asm/entry/32: Really make user_mode() work correctly for VM86 mode
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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