From e2a7d08aa7c51fa903d5294628612a13b4c0d6e0 Mon Sep 17 00:00:00 2001 From: teor Date: Fri, 30 Aug 2019 21:12:52 +1000 Subject: backtrace: Always set a backtrace Tor version We want to report the tor version, even on platforms that don't have backtrace support (like Android). This commit stores the backtrace Tor version, regardless of USE_BACKTRACE. Preparation for 31571. --- src/lib/err/backtrace.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/src/lib/err/backtrace.c b/src/lib/err/backtrace.c index 1d1b3bcfa3..8cca3c37e7 100644 --- a/src/lib/err/backtrace.c +++ b/src/lib/err/backtrace.c @@ -68,10 +68,10 @@ // Redundant with util.h, but doing it here so we can avoid that dependency. #define raw_free free -#ifdef USE_BACKTRACE /** Version of Tor to report in backtrace messages. */ static char bt_version[128] = ""; +#ifdef USE_BACKTRACE /** Largest stack depth to try to dump. */ #define MAX_DEPTH 256 /** Static allocation of stack to dump. This is static so we avoid stack @@ -193,15 +193,12 @@ dump_stack_symbols_to_error_fds(void) /** Install signal handlers as needed so that when we crash, we produce a * useful stack trace. Return 0 on success, -errno on failure. */ static int -install_bt_handler(const char *software) +install_bt_handler(void) { int trap_signals[] = { SIGSEGV, SIGILL, SIGFPE, SIGBUS, SIGSYS, SIGIO, -1 }; int i, rv=0; - strncpy(bt_version, software, sizeof(bt_version) - 1); - bt_version[sizeof(bt_version) - 1] = 0; - struct sigaction sa; memset(&sa, 0, sizeof(sa)); @@ -247,9 +244,8 @@ log_backtrace_impl(int severity, int domain, const char *msg, } static int -install_bt_handler(const char *software) +install_bt_handler(void) { - (void) software; return 0; } @@ -274,7 +270,10 @@ configure_backtrace_handler(const char *tor_version) snprintf(version, sizeof(version), "Tor %s", tor_version); } - return install_bt_handler(version); + strncpy(bt_version, version, sizeof(bt_version) - 1); + bt_version[sizeof(bt_version) - 1] = 0; + + return install_bt_handler(); } /** Perform end-of-process cleanup for code that generates error messages on -- cgit v1.2.3-54-g00ecf From 743bc0028be46e92a46b3b5e38f1e50ee69ff284 Mon Sep 17 00:00:00 2001 From: teor Date: Fri, 30 Aug 2019 21:15:54 +1000 Subject: backtrace: Log the Tor backtrace version whenever we log a backtrace Previously, we just logged it in the crash handler. Part of 31571. --- src/lib/err/backtrace.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/src/lib/err/backtrace.c b/src/lib/err/backtrace.c index 8cca3c37e7..c34eb6dfa6 100644 --- a/src/lib/err/backtrace.c +++ b/src/lib/err/backtrace.c @@ -127,7 +127,7 @@ log_backtrace_impl(int severity, int domain, const char *msg, depth = backtrace(cb_buf, MAX_DEPTH); symbols = backtrace_symbols(cb_buf, (int)depth); - logger(severity, domain, "%s. Stack trace:", msg); + logger(severity, domain, "%s: %s. Stack trace:", bt_version, msg); if (!symbols) { /* LCOV_EXCL_START -- we can't provoke this. */ logger(severity, domain, " Unable to generate backtrace."); @@ -240,7 +240,8 @@ void log_backtrace_impl(int severity, int domain, const char *msg, tor_log_fn logger) { - logger(severity, domain, "%s. (Stack trace not available)", msg); + logger(severity, domain, "%s: %s. (Stack trace not available)", + bt_version, msg); } static int -- cgit v1.2.3-54-g00ecf From 65a1d86491d56c77048d01e0b4fc6b933a13795c Mon Sep 17 00:00:00 2001 From: teor Date: Fri, 30 Aug 2019 21:17:07 +1000 Subject: torerr: Log the Tor backtrace version when a raw assertion fails Part of 31571. --- src/lib/err/backtrace.c | 8 ++++++++ src/lib/err/backtrace.h | 1 + src/lib/err/torerr.c | 3 ++- 3 files changed, 11 insertions(+), 1 deletion(-) diff --git a/src/lib/err/backtrace.c b/src/lib/err/backtrace.c index c34eb6dfa6..a4d8269c6a 100644 --- a/src/lib/err/backtrace.c +++ b/src/lib/err/backtrace.c @@ -261,6 +261,14 @@ dump_stack_symbols_to_error_fds(void) } #endif /* defined(NO_BACKTRACE_IMPL) */ +/** Return the tor version used for error messages on crashes. + * Signal-safe: returns a pointer to a static array. */ +const char * +get_tor_backtrace_version(void) +{ + return bt_version; +} + /** Set up code to handle generating error messages on crashes. */ int configure_backtrace_handler(const char *tor_version) diff --git a/src/lib/err/backtrace.h b/src/lib/err/backtrace.h index 9b313261e6..48b41fca02 100644 --- a/src/lib/err/backtrace.h +++ b/src/lib/err/backtrace.h @@ -21,6 +21,7 @@ void log_backtrace_impl(int severity, int domain, const char *msg, int configure_backtrace_handler(const char *tor_version); void clean_up_backtrace_handler(void); void dump_stack_symbols_to_error_fds(void); +const char *get_tor_backtrace_version(void); #define log_backtrace(sev, dom, msg) \ log_backtrace_impl((sev), (dom), (msg), tor_log) diff --git a/src/lib/err/torerr.c b/src/lib/err/torerr.c index 54acf722aa..88b19b7327 100644 --- a/src/lib/err/torerr.c +++ b/src/lib/err/torerr.c @@ -144,7 +144,8 @@ tor_raw_assertion_failed_msg_(const char *file, int line, const char *expr, { char linebuf[16]; format_dec_number_sigsafe(line, linebuf, sizeof(linebuf)); - tor_log_err_sigsafe("INTERNAL ERROR: Raw assertion failed at ", + tor_log_err_sigsafe("INTERNAL ERROR: Raw assertion failed in ", + get_tor_backtrace_version(), " at ", file, ":", linebuf, ": ", expr, NULL); if (msg) { tor_log_err_sigsafe_write(msg); -- cgit v1.2.3-54-g00ecf From c55591825fedb0fe1db92fab7b654ccc15ad50d3 Mon Sep 17 00:00:00 2001 From: teor Date: Fri, 30 Aug 2019 21:17:56 +1000 Subject: torerr: Try harder to flush raw assert messages before process termination Some platforms (macOS, maybe others?) can swallow the last write before an abort. This issue is probably caused by a race condition between write buffer cache flushing, and process termination. So we write an extra newline, to make sure that the message always gets through. Fixes bug 31571; bugfix on 0.3.5.1-alpha. --- changes/bug31571 | 7 +++++++ src/lib/err/torerr.c | 8 +++++++- 2 files changed, 14 insertions(+), 1 deletion(-) create mode 100644 changes/bug31571 diff --git a/changes/bug31571 b/changes/bug31571 new file mode 100644 index 0000000000..86de3537ba --- /dev/null +++ b/changes/bug31571 @@ -0,0 +1,7 @@ + o Minor bugfixes (error handling): + - Report the tor version whenever an assertion fails. Previously, we only + reported the Tor version on some crashes, and some non-fatal assertions. + Fixes bug 31571; bugfix on 0.3.5.1-alpha. + - On abort, try harder to flush the output buffers of log messages. On + some platforms (macOS), log messages can be discarded when the process + terminates. Fixes bug 31571; bugfix on 0.3.5.1-alpha. diff --git a/src/lib/err/torerr.c b/src/lib/err/torerr.c index 88b19b7327..6b5224273a 100644 --- a/src/lib/err/torerr.c +++ b/src/lib/err/torerr.c @@ -146,13 +146,19 @@ tor_raw_assertion_failed_msg_(const char *file, int line, const char *expr, format_dec_number_sigsafe(line, linebuf, sizeof(linebuf)); tor_log_err_sigsafe("INTERNAL ERROR: Raw assertion failed in ", get_tor_backtrace_version(), " at ", - file, ":", linebuf, ": ", expr, NULL); + file, ":", linebuf, ": ", expr, "\n", NULL); if (msg) { tor_log_err_sigsafe_write(msg); tor_log_err_sigsafe_write("\n"); } dump_stack_symbols_to_error_fds(); + + /* Some platforms (macOS, maybe others?) can swallow the last write before an + * abort. This issue is probably caused by a race condition between write + * buffer cache flushing, and process termination. So we write an extra + * newline, to make sure that the message always gets through. */ + tor_log_err_sigsafe_write("\n"); } /* As format_{hex,dex}_number_sigsafe, but takes a radix argument -- cgit v1.2.3-54-g00ecf From f311d0676caad1c61a4dbf8fffbeb79003866903 Mon Sep 17 00:00:00 2001 From: teor Date: Tue, 3 Sep 2019 15:50:37 +1000 Subject: backtrace: Check the return values of snprintf() and strncpy() We can't use strlcat() or strlcpy() in torerr, because they are defined in string/compat_string.h on some platforms, and string uses torerr. Part of 31571. --- src/lib/err/backtrace.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/src/lib/err/backtrace.c b/src/lib/err/backtrace.c index a4d8269c6a..8606f42177 100644 --- a/src/lib/err/backtrace.c +++ b/src/lib/err/backtrace.c @@ -276,11 +276,23 @@ configure_backtrace_handler(const char *tor_version) char version[128] = "Tor\0"; if (tor_version) { - snprintf(version, sizeof(version), "Tor %s", tor_version); + int snp_rv = 0; + /* We can't use strlcat() here, because it is defined in + * string/compat_string.h on some platforms, and string uses torerr. */ + snp_rv = snprintf(version, sizeof(version), "Tor %s", tor_version); + /* It's safe to call raw_assert() here, because raw_assert() does not + * call configure_backtrace_handler(). */ + raw_assert(snp_rv < (int)sizeof(version)); + raw_assert(snp_rv >= 0); } - strncpy(bt_version, version, sizeof(bt_version) - 1); + char *str_rv = NULL; + /* We can't use strlcpy() here, see the note about strlcat() above. */ + str_rv = strncpy(bt_version, version, sizeof(bt_version) - 1); + /* We must terminate bt_version, then raw_assert(), because raw_assert() + * uses bt_version. */ bt_version[sizeof(bt_version) - 1] = 0; + raw_assert(str_rv == bt_version); return install_bt_handler(); } -- cgit v1.2.3-54-g00ecf