backport of:
From 13718030ad4b3209a7583b4f27f683cd3a6fa5f2 Mon Sep 17 00:00:00 2001
From: Harry Sintonen <sintonen@iki.fi>
Date: Tue, 25 Apr 2023 09:22:26 +0200
Subject: [PATCH] hostip: add locks around use of global buffer for alarm()
When building with the sync name resolver and timeout ability we now
require thread-safety to be present to enable it.
Closes #11030
---
lib/hostip.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/lib/hostip.c b/lib/hostip.c
index 2381290fdd43e..e410cda69ae6e 100644
--- a/lib/hostip.c
+++ b/lib/hostip.c
@@ -70,12 +70,19 @@
#include "curl_memory.h"
#include "memdebug.h"
-#if defined(CURLRES_SYNCH) && \
- defined(HAVE_ALARM) && defined(SIGALRM) && defined(HAVE_SIGSETJMP)
+#if defined(CURLRES_SYNCH) && \
+ defined(HAVE_ALARM) && \
+ defined(SIGALRM) && \
+ defined(HAVE_SIGSETJMP) && \
+ defined(GLOBAL_INIT_IS_THREADSAFE)
/* alarm-based timeouts can only be used with all the dependencies satisfied */
#define USE_ALARM_TIMEOUT
#endif
+#ifdef USE_ALARM_TIMEOUT
+#include "easy_lock.h"
+#endif
+
#define MAX_HOSTCACHE_LEN (255 + 7) /* max FQDN + colon + port number + zero */
/*
@@ -254,11 +261,12 @@ void Curl_hostcache_prune(struct Curl_easy *data)
Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
}
-#ifdef HAVE_SIGSETJMP
+#ifdef USE_ALARM_TIMEOUT
/* Beware this is a global and unique instance. This is used to store the
return address that we can jump back to from inside a signal handler. This
is not thread-safe stuff. */
sigjmp_buf curl_jmpenv;
+curl_simple_lock curl_jmpenv_lock;
#endif
/* lookup address, returns entry if found and not stale */
@@ -832,7 +840,6 @@ enum resolve_t Curl_resolv(struct Curl_easy *data,
static
RETSIGTYPE alarmfunc(int sig)
{
- /* this is for "-ansi -Wall -pedantic" to stop complaining! (rabe) */
(void)sig;
siglongjmp(curl_jmpenv, 1);
}
@@ -912,6 +919,8 @@ enum resolve_t Curl_resolv_timeout(struct Curl_easy *data,
This should be the last thing we do before calling Curl_resolv(),
as otherwise we'd have to worry about variables that get modified
before we invoke Curl_resolv() (and thus use "volatile"). */
+ curl_simple_lock_lock(&curl_jmpenv_lock);
+
if(sigsetjmp(curl_jmpenv, 1)) {
/* this is coming from a siglongjmp() after an alarm signal */
failf(data, "name lookup timed out");
@@ -980,6 +989,8 @@ enum resolve_t Curl_resolv_timeout(struct Curl_easy *data,
#endif
#endif /* HAVE_SIGACTION */
+ curl_simple_lock_unlock(&curl_jmpenv_lock);
+
/* switch back the alarm() to either zero or to what it was before minus
the time we spent until now! */
if(prev_alarm) {
diff --git a/lib/easy_lock.h b/lib/easy_lock.h
index 0000000..e410cda69ae6e 100644
--- /dev/null
+++ b/lib/easy_lock.h
@@ -0,0 +0,109 @@
+#ifndef HEADER_CURL_EASY_LOCK_H
+#define HEADER_CURL_EASY_LOCK_H
+/***************************************************************************
+ * _ _ ____ _
+ * Project ___| | | | _ \| |
+ * / __| | | | |_) | |
+ * | (__| |_| | _ <| |___
+ * \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ * SPDX-License-Identifier: curl
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+
+#define GLOBAL_INIT_IS_THREADSAFE
+
+#if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x600
+
+#ifdef __MINGW32__
+#ifndef __MINGW64_VERSION_MAJOR
+#if (__MINGW32_MAJOR_VERSION < 5) || \
+ (__MINGW32_MAJOR_VERSION == 5 && __MINGW32_MINOR_VERSION == 0)
+/* mingw >= 5.0.1 defines SRWLOCK, and slightly different from MS define */
+typedef PVOID SRWLOCK, *PSRWLOCK;
+#endif
+#endif
+#ifndef SRWLOCK_INIT
+#define SRWLOCK_INIT NULL
+#endif
+#endif /* __MINGW32__ */
+
+#define curl_simple_lock SRWLOCK
+#define CURL_SIMPLE_LOCK_INIT SRWLOCK_INIT
+
+#define curl_simple_lock_lock(m) AcquireSRWLockExclusive(m)
+#define curl_simple_lock_unlock(m) ReleaseSRWLockExclusive(m)
+
+#elif defined(HAVE_ATOMIC) && defined(HAVE_STDATOMIC_H)
+#include <stdatomic.h>
+#if defined(HAVE_SCHED_YIELD)
+#include <sched.h>
+#endif
+
+#define curl_simple_lock atomic_int
+#define CURL_SIMPLE_LOCK_INIT 0
+
+/* a clang-thing */
+#ifndef __has_builtin
+#define __has_builtin(x) 0
+#endif
+
+#ifndef __INTEL_COMPILER
+/* The Intel compiler tries to look like GCC *and* clang *and* lies in its
+ __has_builtin() function, so override it. */
+
+/* if GCC on i386/x86_64 or if the built-in is present */
+#if ( (defined(__GNUC__) && !defined(__clang__)) && \
+ (defined(__i386__) || defined(__x86_64__))) || \
+ __has_builtin(__builtin_ia32_pause)
+#define HAVE_BUILTIN_IA32_PAUSE
+#endif
+
+#endif
+
+static inline void curl_simple_lock_lock(curl_simple_lock *lock)
+{
+ for(;;) {
+ if(!atomic_exchange_explicit(lock, true, memory_order_acquire))
+ break;
+ /* Reduce cache coherency traffic */
+ while(atomic_load_explicit(lock, memory_order_relaxed)) {
+ /* Reduce load (not mandatory) */
+#ifdef HAVE_BUILTIN_IA32_PAUSE
+ __builtin_ia32_pause();
+#elif defined(__aarch64__)
+ __asm__ volatile("yield" ::: "memory");
+#elif defined(HAVE_SCHED_YIELD)
+ sched_yield();
+#endif
+ }
+ }
+}
+
+static inline void curl_simple_lock_unlock(curl_simple_lock *lock)
+{
+ atomic_store_explicit(lock, false, memory_order_release);
+}
+
+#else
+
+#undef GLOBAL_INIT_IS_THREADSAFE
+
+#endif
+
+#endif /* HEADER_CURL_EASY_LOCK_H */
