From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f70.google.com (mail-pl0-f70.google.com [209.85.160.70]) by kanga.kvack.org (Postfix) with ESMTP id A14596B0280 for ; Sun, 17 Jun 2018 07:49:32 -0400 (EDT) Received: by mail-pl0-f70.google.com with SMTP id i1-v6so8240255pld.11 for ; Sun, 17 Jun 2018 04:49:32 -0700 (PDT) Received: from mail.kernel.org (mail.kernel.org. [198.145.29.99]) by mx.google.com with ESMTPS id n11-v6si12517427plg.230.2018.06.17.04.49.31 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 17 Jun 2018 04:49:31 -0700 (PDT) Subject: Patch "x86/pkeys/selftests: Avoid printf-in-signal deadlocks" has been added to the 4.16-stable tree From: Date: Sun, 17 Jun 2018 13:23:53 +0200 Message-ID: <152923463324762@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: 20180509171344.C53FD2F3@viggo.jf.intel.com, akpm@linux-foundation.org, alexander.levin@microsoft.com, dave.hansen@intel.com, dave.hansen@linux.intel.com, gregkh@linuxfoundation.org, linux-mm@kvack.org, linuxram@us.ibm.com, mingo@kernel.org, mpe@ellerman.id.au, peterz@infradead.org, shuah@kernel.org, tglx@linutronix.de, torvalds@linux-foundation.org Cc: stable-commits@vger.kernel.org This is a note to let you know that I've just added the patch titled x86/pkeys/selftests: Avoid printf-in-signal deadlocks to the 4.16-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-pkeys-selftests-avoid-printf-in-signal-deadlocks.patch and it can be found in the queue-4.16 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From foo@baz Sun Jun 17 12:07:34 CEST 2018 From: Dave Hansen Date: Wed, 9 May 2018 10:13:44 -0700 Subject: x86/pkeys/selftests: Avoid printf-in-signal deadlocks From: Dave Hansen [ Upstream commit caf9eb6b4c82fc6cbd03697052ff22d97b0c377b ] printf() and friends are unusable in signal handlers. They deadlock. The pkey selftest does not do any normal printing in signal handlers, only extra debugging. So, just print the format string so we get *some* output when debugging. Signed-off-by: Dave Hansen Cc: Andrew Morton Cc: Dave Hansen Cc: Linus Torvalds Cc: Michael Ellermen Cc: Peter Zijlstra Cc: Ram Pai Cc: Shuah Khan Cc: Thomas Gleixner Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20180509171344.C53FD2F3@viggo.jf.intel.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- tools/testing/selftests/x86/pkey-helpers.h | 20 ++++++++------------ 1 file changed, 8 insertions(+), 12 deletions(-) --- a/tools/testing/selftests/x86/pkey-helpers.h +++ b/tools/testing/selftests/x86/pkey-helpers.h @@ -26,30 +26,26 @@ static inline void sigsafe_printf(const { va_list ap; - va_start(ap, format); if (!dprint_in_signal) { + va_start(ap, format); vprintf(format, ap); + va_end(ap); } else { int ret; - int len = vsnprintf(dprint_in_signal_buffer, - DPRINT_IN_SIGNAL_BUF_SIZE, - format, ap); /* - * len is amount that would have been printed, - * but actual write is truncated at BUF_SIZE. + * No printf() functions are signal-safe. + * They deadlock easily. Write the format + * string to get some output, even if + * incomplete. */ - if (len > DPRINT_IN_SIGNAL_BUF_SIZE) - len = DPRINT_IN_SIGNAL_BUF_SIZE; - ret = write(1, dprint_in_signal_buffer, len); + ret = write(1, format, strlen(format)); if (ret < 0) - abort(); + exit(1); } - va_end(ap); } #define dprintf_level(level, args...) do { \ if (level <= DEBUG_LEVEL) \ sigsafe_printf(args); \ - fflush(NULL); \ } while (0) #define dprintf0(args...) dprintf_level(0, args) #define dprintf1(args...) dprintf_level(1, args) Patches currently in stable-queue which might be from dave.hansen@linux.intel.com are queue-4.16/x86-pkeys-selftests-factor-out-instruction-page.patch queue-4.16/x86-pkeys-selftests-fix-pointer-math.patch queue-4.16/x86-pkeys-selftests-adjust-the-self-test-to-fresh-distros-that-export-the-pkeys-abi.patch queue-4.16/x86-pkeys-selftests-add-a-test-for-pkey-0.patch queue-4.16/x86-pkeys-selftests-stop-using-assert.patch queue-4.16/x86-pkeys-selftests-save-off-prot-for-allocations.patch queue-4.16/x86-pkeys-selftests-remove-dead-debugging-code-fix-dprint_in_signal.patch queue-4.16/x86-mpx-selftests-adjust-the-self-test-to-fresh-distros-that-export-the-mpx-abi.patch queue-4.16/x86-pkeys-selftests-add-prot_exec-test.patch queue-4.16/x86-pkeys-selftests-allow-faults-on-unknown-keys.patch queue-4.16/x86-pkeys-selftests-give-better-unexpected-fault-error-messages.patch queue-4.16/x86-pkeys-selftests-avoid-printf-in-signal-deadlocks.patch queue-4.16/x86-pkeys-selftests-fix-pkey-exhaustion-test-off-by-one.patch