From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kees Cook Subject: [PATCH 3/3] bug: Fix "cut here" location for __WARN_TAINT architectures Date: Tue, 7 Nov 2017 16:27:49 -0800 Message-ID: <1510100869-73751-4-git-send-email-keescook@chromium.org> References: <1510100869-73751-1-git-send-email-keescook@chromium.org> Return-path: Received: from mail-pl0-f67.google.com ([209.85.160.67]:45944 "EHLO mail-pl0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933938AbdKHA2B (ORCPT ); Tue, 7 Nov 2017 19:28:01 -0500 Received: by mail-pl0-f67.google.com with SMTP id 30so139549pla.2 for ; Tue, 07 Nov 2017 16:28:01 -0800 (PST) In-Reply-To: <1510100869-73751-1-git-send-email-keescook@chromium.org> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Andrew Morton Cc: Kees Cook , Peter Zijlstra , Josh Poimboeuf , Fengguang Wu , Arnd Bergmann , linux-arch@vger.kernel.org, Joe Perches , linux-am33-list@redhat.com, linux-kernel@vger.kernel.org Prior to v4.11, x86 used warn_slowpath_fmt() for handling WARN()s. After WARN() was moved to using UD0 on x86, the warning text started appearing _before_ the "cut here" line. This appears to have been a long-standing bug on architectures that used __WARN_TAINT, but it didn't get fixed. v4.11 and earlier on x86: [ 7.944142] ------------[ cut here ]------------ [ 7.945631] WARNING: CPU: 0 PID: 2956 at drivers/misc/lkdtm_bugs.c:65 lkdtm_WARNING+0x21/0x30 [ 7.947453] This is a warning message [ 7.948357] Modules linked in: v4.12 and later on x86: [ 8.973063] This is a warning message [ 8.973885] ------------[ cut here ]------------ [ 8.974867] WARNING: CPU: 1 PID: 2982 at drivers/misc/lkdtm_bugs.c:68 lkdtm_WARNING+0x15/0x20 [ 8.976563] Modules linked in: With this fix: [ 9.157133] ------------[ cut here ]------------ [ 9.158143] This is a warning message [ 9.159099] WARNING: CPU: 3 PID: 3009 at drivers/misc/lkdtm_bugs.c:67 lkdtm_WARNING+0x15/0x20 Since the __FILE__ reporting happens as part of the UD0 handler, it isn't trivial to move the message to after the WARNING line, but at least we can fix the position of the "cut here" line so all the various logging tools will start including the actual runtime warning message again, when they follow the instruction and "cut here". Fixes: 9a93848fe787 ("x86/debug: Implement __WARN() using UD0") Cc: Peter Zijlstra (Intel) Cc: Josh Poimboeuf Cc: Fengguang Wu Cc: Arnd Bergmann Cc: linux-arch@vger.kernel.org Signed-off-by: Kees Cook --- include/asm-generic/bug.h | 5 +++-- kernel/panic.c | 16 +++++++++++++++- 2 files changed, 18 insertions(+), 3 deletions(-) diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h index 673a79dd3928..30b22e47a7e9 100644 --- a/include/asm-generic/bug.h +++ b/include/asm-generic/bug.h @@ -91,10 +91,11 @@ extern void warn_slowpath_null(const char *file, const int line); #define __WARN_printf_taint(taint, arg...) \ warn_slowpath_fmt_taint(__FILE__, __LINE__, taint, arg) #else +extern __printf(1, 2) void __warn_printk(const char *fmt, ...); #define __WARN() __WARN_TAINT(TAINT_WARN) -#define __WARN_printf(arg...) do { printk(arg); __WARN(); } while (0) +#define __WARN_printf(arg...) do { __warn_printk(arg); __WARN(); } while (0) #define __WARN_printf_taint(taint, arg...) \ - do { printk(arg); __WARN_TAINT(taint); } while (0) + do { __warn_printk(arg); __WARN_TAINT(taint); } while (0) #endif /* used internally by panic.c */ diff --git a/kernel/panic.c b/kernel/panic.c index ab210714f2f3..65c9e7b942ea 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -518,7 +518,8 @@ void __warn(const char *file, int line, void *caller, unsigned taint, { disable_trace_on_warning(); - pr_warn(CUT_HERE); + if (args) + pr_warn(CUT_HERE); if (file) pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n", @@ -582,9 +583,22 @@ EXPORT_SYMBOL(warn_slowpath_fmt_taint); void warn_slowpath_null(const char *file, int line) { + pr_warn(CUT_HERE); __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL, NULL); } EXPORT_SYMBOL(warn_slowpath_null); +#else +void __warn_printk(const char *fmt, ...) +{ + va_list args; + + pr_warn(CUT_HERE); + + va_start(args, fmt); + vprintk(fmt, args); + va_end(args); +} +EXPORT_SYMBOL(__warn_printk); #endif #ifdef CONFIG_CC_STACKPROTECTOR -- 2.7.4