From: Kees Cook <keescook@xxxxxxxxxxxx> Subject: bug: fix "cut here" location for __WARN_TAINT architectures 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". Link: http://lkml.kernel.org/r/1510100869-73751-4-git-send-email-keescook@xxxxxxxxxxxx Fixes: 9a93848fe787 ("x86/debug: Implement __WARN() using UD0") Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Cc: Fengguang Wu <fengguang.wu@xxxxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/asm-generic/bug.h | 5 +++-- kernel/panic.c | 16 +++++++++++++++- 2 files changed, 18 insertions(+), 3 deletions(-) diff -puN include/asm-generic/bug.h~bug-fix-cut-here-location-for-__warn_taint-architectures include/asm-generic/bug.h --- a/include/asm-generic/bug.h~bug-fix-cut-here-location-for-__warn_taint-architectures +++ a/include/asm-generic/bug.h @@ -92,10 +92,11 @@ extern void warn_slowpath_null(const cha #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 -puN kernel/panic.c~bug-fix-cut-here-location-for-__warn_taint-architectures kernel/panic.c --- a/kernel/panic.c~bug-fix-cut-here-location-for-__warn_taint-architectures +++ a/kernel/panic.c @@ -520,7 +520,8 @@ void __warn(const char *file, int line, { 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", @@ -584,9 +585,22 @@ 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_BUG _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
