Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757655AbaLJOXr (ORCPT ); Wed, 10 Dec 2014 09:23:47 -0500 Received: from e06smtp15.uk.ibm.com ([195.75.94.111]:50194 "EHLO e06smtp15.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757448AbaLJOXm (ORCPT ); Wed, 10 Dec 2014 09:23:42 -0500 From: David Hildenbrand To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Cc: benh@kernel.crashing.org, paulus@samba.org, akpm@linux-foundation.org, heiko.carstens@de.ibm.com, dahi@linux.vnet.ibm.com, schwidefsky@de.ibm.com, borntraeger@de.ibm.com, mst@redhat.com, tglx@linutronix.de, David.Laight@ACULAB.COM, peterz@infradead.org, hughd@google.com, hocko@suse.cz Subject: [PATCH v2 0/5] Reenable might_sleep() checks for might_fault() Date: Wed, 10 Dec 2014 15:23:29 +0100 Message-Id: <1418221414-60110-1-git-send-email-dahi@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.5.5 X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14121014-0021-0000-0000-00000216B9C5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org v1 -> v2: - moved pagefault_count to the end of thread_info for all archs that would have required manually calculating asm-offsets - to keep changes minimal. - remove unlikely() from "mm, uaccess: trigger might_sleep() in" and keep changes minimal (in_atomic() -> pagefault_disabled()) ---- I recently discovered that might_fault() doesn't call might_sleep() anymore. Therefore bugs like: spin_lock(&lock); rc = copy_to_user(...); spin_unlock(&lock); would not be detected with CONFIG_DEBUG_ATOMIC_SLEEP. The code was changed to disable false positives for code like: pagefault_disable(); rc = copy_to_user(...); pagefault_enable(); Until now, pagefault_disable() and pagefault_enable() simply modified the preempt count, therefore telling the pagefault handler that the context is atomic and sleeping is disallowed. In order to reenable might_sleep() checks for the correct path, we need a way to detect whether we run in a pagefault_disable() context. This series therefore introduces a separate pagefault_count and uses it to count the levels of pagefault_disable() per thread. might_sleep() checks are reactivated for the !pagefault_disable() path. So this should now work: spin_lock(&lock); /* also if left away */ pagefault_disable() rc = copy_to_user(...); pagefault_enable(); spin_unlock(&lock); And this should report a warning again: spin_lock(&lock); rc = copy_to_user(...); spin_unlock(&lock); Please note that this series will not completely split the handling of pagefault_disable() and the preempt count. This will be done in another series. Purpose of this series is to reenable might_sleep() checks for might_fault(), avoiding to produce false positives. Cross compiled on powerpc, arm, sparc, sparc64, arm64, x86_64, i386, mips, alpha, ia64, xtensa, m68k, microblaze. Tested on s390. David Hildenbrand (5): uaccess: add pagefault_count to thread_info uaccess: count pagefault_disable() levels in pagefault_count mm, uaccess: trigger might_sleep() in might_fault() when pagefaults are disabled uaccess: clarify that uaccess may only sleep if pagefaults are not disabled uaccess: CONFIG_DEBUG_PAGEFAULT_COUNT to debug pagefault_count arch/alpha/include/asm/thread_info.h | 1 + arch/arc/include/asm/thread_info.h | 1 + arch/arm/include/asm/thread_info.h | 1 + arch/arm64/include/asm/thread_info.h | 1 + arch/avr32/include/asm/thread_info.h | 1 + arch/avr32/include/asm/uaccess.h | 12 +++++--- arch/blackfin/include/asm/thread_info.h | 1 + arch/c6x/include/asm/thread_info.h | 1 + arch/cris/include/asm/thread_info.h | 1 + arch/frv/include/asm/thread_info.h | 1 + arch/hexagon/include/asm/thread_info.h | 1 + arch/hexagon/include/asm/uaccess.h | 3 +- arch/ia64/include/asm/thread_info.h | 1 + arch/m32r/include/asm/thread_info.h | 1 + arch/m32r/include/asm/uaccess.h | 30 ++++++++++++------ arch/m68k/include/asm/thread_info.h | 1 + arch/metag/include/asm/thread_info.h | 1 + arch/microblaze/include/asm/thread_info.h | 1 + arch/microblaze/include/asm/uaccess.h | 6 ++-- arch/mips/include/asm/thread_info.h | 1 + arch/mips/include/asm/uaccess.h | 45 ++++++++++++++++++--------- arch/mn10300/include/asm/thread_info.h | 1 + arch/openrisc/include/asm/thread_info.h | 1 + arch/parisc/include/asm/thread_info.h | 1 + arch/powerpc/include/asm/thread_info.h | 1 + arch/s390/include/asm/thread_info.h | 1 + arch/s390/include/asm/uaccess.h | 15 ++++++--- arch/score/include/asm/thread_info.h | 1 + arch/score/include/asm/uaccess.h | 15 ++++++--- arch/sh/include/asm/thread_info.h | 1 + arch/sparc/include/asm/thread_info_32.h | 1 + arch/sparc/include/asm/thread_info_64.h | 1 + arch/tile/include/asm/thread_info.h | 1 + arch/tile/include/asm/uaccess.h | 21 ++++++++----- arch/um/include/asm/thread_info.h | 1 + arch/unicore32/include/asm/thread_info.h | 1 + arch/x86/include/asm/thread_info.h | 1 + arch/x86/include/asm/uaccess.h | 15 ++++++--- arch/x86/include/asm/uaccess_32.h | 6 ++-- arch/x86/lib/usercopy_32.c | 6 ++-- arch/xtensa/include/asm/thread_info.h | 1 + include/linux/kernel.h | 3 +- include/linux/uaccess.h | 51 ++++++++++++++++++++++++++----- lib/Kconfig.debug | 9 ++++++ lib/strnlen_user.c | 6 ++-- mm/maccess.c | 11 +++++++ mm/memory.c | 18 ++++------- 47 files changed, 222 insertions(+), 80 deletions(-) -- 1.8.5.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/