This is a note to let you know that I've just added the patch titled

selftests/x86/ldt_gdt: Robustify against set_thread_area() and LAR oddities

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: selftests-x86-ldt_gdt-robustify-against-set_thread_area-and-lar-oddities.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Wed Dec 6 18:04:41 CET 2017

From: Andy Lutomirski luto@kernel.org Date: Sat, 4 Nov 2017 04:19:49 -0700 Subject: selftests/x86/ldt_gdt: Robustify against set_thread_area() and LAR oddities

From: Andy Lutomirski luto@kernel.org

[ Upstream commit d60ad744c9741586010d4bea286f09a063a90fbd ]

Bits 19:16 of LAR's result are undefined, and some upcoming improvements to the test case seem to trigger this. Mask off those bits to avoid spurious failures.

commit 5b781c7e317f ("x86/tls: Forcibly set the accessed bit in TLS segments") adds a valid case in which LAR's output doesn't quite agree with set_thread_area()'s input. This isn't triggered in the test as is, but it will be if we start calling set_thread_area() with the accessed bit clear. Work around this discrepency.

I've added a Fixes tag so that -stable can pick this up if neccesary.

Signed-off-by: Andy Lutomirski luto@kernel.org Cc: Borislav Petkov bpetkov@suse.de Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Fixes: 5b781c7e317f ("x86/tls: Forcibly set the accessed bit in TLS segments") Link: http://lkml.kernel.org/r/b82f3f89c034b53580970ac865139fd8863f44e2.1509794321... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/testing/selftests/x86/ldt_gdt.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/tools/testing/selftests/x86/ldt_gdt.c +++ b/tools/testing/selftests/x86/ldt_gdt.c @@ -115,7 +115,15 @@ static void check_valid_segment(uint16_t return; }

- if (ar != expected_ar) { + /* The SDM says "bits 19:16 are undefined". Thanks. */ + ar &= ~0xF0000; + + /* + * NB: Different Linux versions do different things with the + * accessed bit in set_thread_area(). + */ + if (ar != expected_ar && + (ldt || ar != (expected_ar | AR_ACCESSED))) { printf("[FAIL]\t%s entry %hu has AR 0x%08X but expected 0x%08X\n", (ldt ? "LDT" : "GDT"), index, ar, expected_ar); nerrs++;

Patches currently in stable-queue which might be from luto@kernel.org are

queue-4.14/selftests-x86-ldt_get-add-a-few-additional-tests-for-limits.patch queue-4.14/selftests-x86-ldt_gdt-robustify-against-set_thread_area-and-lar-oddities.patch queue-4.14/x86-entry-use-syscall_define-macros-for-sys_modify_ldt.patch