From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <1523041723.6127.33.camel@perches.com> Subject: s390: defective uses of va_arg in __debug_sprintf_event From: Joe Perches Date: Fri, 06 Apr 2018 12:08:43 -0700 Content-Type: text/plain; charset="ISO-8859-1" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Martin Schwidefsky , Heiko Carstens Cc: linux-s390@vger.kernel.org, LKML , Rasmus Villemoes , Petr Mladek List-ID: debug_sprintf_event calls __debug_sprintf_event with a format and arguments. There various types of arguments used in these call, but __debug_sprintf_event uses va_arg with only long as the type argument so random errors could occur because the type and argument are supposed to match. debug_entry_t *__debug_sprintf_event(debug_info_t *id, int level, char *string, ...) { [...] va_start(ap, string); curr_event->string = string; for (idx = 0; idx < min(numargs, (int)(id->buf_size / sizeof(long)) - 1); idx++) curr_event->args[idx] = va_arg(ap, long); va_end(ap); [...] } from man va_arg va_arg() if type is not compatible with the type of the actual next argument (as promoted according to the default argument promotions), random errors will occur. For instance, uses like: arch/s390/kernel/perf_cpum_sf.c:919: debug_sprintf_event(sfdbg, 6, "pmu_enable: es=%i cs=%i ed=%i cd=%i " arch/s390/kernel/perf_cpum_sf.c-920- "tear=%p dear=%p\n", cpuhw->lsctl.es, cpuhw->lsctl.cs, arch/s390/kernel/perf_cpum_sf.c-921- cpuhw->lsctl.ed, cpuhw->lsctl.cd, arch/s390/kernel/perf_cpum_sf.c-922- (void *) cpuhw->lsctl.tear, (void *) cpuhw->lsctl.dear); where the first 3 arguments are int but their type as used by va_arg in __debug_sprintf_event is long which could produce random errors. Instead of adding complete format % decoding, perhaps the easiest solution is to change all the formats to use %lu or %ld and cast each argument as appropriate. And I found this when looking at another defect in debug_sprintf_event where a %p extension is unintentionally used via a string concatenation. as pointed out by Rasmus Villemoes --- arch/s390/kernel/perf_cpum_sf.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c index 1c9ddd7aa5ec..1c449a6f841a 100644 --- a/arch/s390/kernel/perf_cpum_sf.c +++ b/arch/s390/kernel/perf_cpum_sf.c @@ -212,9 +212,7 @@ static int realloc_sampling_buffer(struct sf_buffer *sfb, * the sampling buffer origin. */ if (sfb->sdbt != get_next_sdbt(tail)) { - debug_sprintf_event(sfdbg, 3, "realloc_sampling_buffer: " - "sampling buffer is not linked: origin=%p" - "tail=%p\n", + debug_sprintf_event(sfdbg, 3, "realloc_sampling_buffer: sampling buffer is not linked: origin=%p tail=%p\n", (void *) sfb->sdbt, (void *) tail); return -EINVAL; }