108 lines
3.1 KiB
Diff
108 lines
3.1 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Martin Wilck <mwilck@suse.com>
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Date: Thu, 15 Oct 2020 16:13:14 +0200
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Subject: [PATCH] libmultipath: fix race between log_safe and log_thread_stop()
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log_safe() could race with log_thread_stop(); simply
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checking the value of log_thr has never been safe. By converting the
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mutexes to static initializers, we avoid having to destroy them, and thus
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possibly accessing a destroyed mutex in log_safe(). Furthermore, taking
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both the logev_lock and the logq_lock makes sure the logarea isn't freed
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while we are writing to it.
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Reviewed-by: Benjamin Marzinski <bmarzins@redhat.com>
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Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
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---
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libmultipath/log_pthread.c | 48 +++++++++++++++++++++-----------------
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1 file changed, 26 insertions(+), 22 deletions(-)
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diff --git a/libmultipath/log_pthread.c b/libmultipath/log_pthread.c
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index 3a2566ae..0d48c52c 100644
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--- a/libmultipath/log_pthread.c
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+++ b/libmultipath/log_pthread.c
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@@ -17,31 +17,42 @@
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static pthread_t log_thr;
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-static pthread_mutex_t logq_lock;
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-static pthread_mutex_t logev_lock;
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-static pthread_cond_t logev_cond;
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+/* logev_lock must not be taken with logq_lock held */
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+static pthread_mutex_t logq_lock = PTHREAD_MUTEX_INITIALIZER;
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+static pthread_mutex_t logev_lock = PTHREAD_MUTEX_INITIALIZER;
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+static pthread_cond_t logev_cond = PTHREAD_COND_INITIALIZER;
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static int logq_running;
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static int log_messages_pending;
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void log_safe (int prio, const char * fmt, va_list ap)
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{
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+ bool running;
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+
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if (prio > LOG_DEBUG)
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prio = LOG_DEBUG;
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- if (log_thr == (pthread_t)0) {
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- vsyslog(prio, fmt, ap);
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- return;
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- }
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+ /*
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+ * logev_lock protects logq_running. By holding it, we avoid a race
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+ * with log_thread_stop() -> log_close(), which would free the logarea.
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+ */
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+ pthread_mutex_lock(&logev_lock);
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+ pthread_cleanup_push(cleanup_mutex, &logev_lock);
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+ running = logq_running;
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- pthread_mutex_lock(&logq_lock);
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- log_enqueue(prio, fmt, ap);
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- pthread_mutex_unlock(&logq_lock);
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+ if (running) {
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+ pthread_mutex_lock(&logq_lock);
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+ pthread_cleanup_push(cleanup_mutex, &logq_lock);
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+ log_enqueue(prio, fmt, ap);
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+ pthread_cleanup_pop(1);
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- pthread_mutex_lock(&logev_lock);
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- log_messages_pending = 1;
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- pthread_cond_signal(&logev_cond);
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- pthread_mutex_unlock(&logev_lock);
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+ log_messages_pending = 1;
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+ pthread_cond_signal(&logev_cond);
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+ }
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+ pthread_cleanup_pop(1);
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+
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+ if (!running)
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+ vsyslog(prio, fmt, ap);
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}
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static void flush_logqueue (void)
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@@ -103,9 +114,6 @@ void log_thread_start (pthread_attr_t *attr)
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int running = 0;
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logdbg(stderr,"enter log_thread_start\n");
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- pthread_mutex_init(&logq_lock, NULL);
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- pthread_mutex_init(&logev_lock, NULL);
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- pthread_cond_init(&logev_cond, NULL);
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if (log_init("multipathd", 0)) {
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fprintf(stderr,"can't initialize log buffer\n");
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@@ -154,13 +162,9 @@ void log_thread_stop (void)
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}
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pthread_cleanup_pop(1);
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- flush_logqueue();
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if (running)
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pthread_join(log_thr, NULL);
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- pthread_mutex_destroy(&logq_lock);
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- pthread_mutex_destroy(&logev_lock);
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- pthread_cond_destroy(&logev_cond);
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-
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+ flush_logqueue();
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log_close();
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}
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--
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2.17.2
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