Fix: fd tracker: do not allow signal handlers to close lttng-ust FDs

[lttng-ust.git] / liblttng-ust-comm / lttng-ust-fd-tracker.c

diff --git a/liblttng-ust-comm/lttng-ust-fd-tracker.c b/liblttng-ust-comm/lttng-ust-fd-tracker.c
index 9659f349e54ac85a3afad50b2cfc2055abcfacfc..42c3984cc2d3a390f941005f82a0315aa329c208 100644 (file)
--- a/liblttng-ust-comm/lttng-ust-fd-tracker.c
+++ b/liblttng-ust-comm/lttng-ust-fd-tracker.c
@@ -77,12 +77,20 @@ static int ust_safe_guard_saved_cancelstate;
 
 /*
  * Track whether we are within lttng-ust or application, for close
- * system call override by LD_PRELOAD library. This also tracks whether
- * we are invoking close() from a signal handler nested on an
- * application thread.
+ * system call override by LD_PRELOAD library. Threads registered
+ * as being lttng-ust listener threads need to perform fd tracker
+ * locking explicitly around their use of file descriptor manipulation
+ * functions.
+ */
+static DEFINE_URCU_TLS(int, thread_fd_tracking);
+
+/*
+ * Track whether we are invoking close() from a signal handler nested on
+ * an application thread.
  */
 static DEFINE_URCU_TLS(int, ust_fd_mutex_nest);
 
+
 /* fd_set used to book keep fd being used by lttng-ust. */
 static fd_set *lttng_fd_set;
 static int lttng_ust_max_fd;
@@ -94,6 +102,7 @@ static int init_done;
  */
 void lttng_ust_fixup_fd_tracker_tls(void)
 {
+       asm volatile ("" : : "m" (URCU_TLS(thread_fd_tracking)));
        asm volatile ("" : : "m" (URCU_TLS(ust_fd_mutex_nest)));
 }
 
@@ -348,7 +357,7 @@ int lttng_ust_safe_close_fd(int fd, int (*close_cb)(int fd))
         * If called from lttng-ust, we directly call close without
         * validating whether the FD is part of the tracked set.
         */
-       if (URCU_TLS(ust_fd_mutex_nest))
+       if (URCU_TLS(thread_fd_tracking))
                return close_cb(fd);
 
        lttng_ust_lock_fd_tracker();
@@ -384,7 +393,7 @@ int lttng_ust_safe_fclose_stream(FILE *stream, int (*fclose_cb)(FILE *stream))
         * If called from lttng-ust, we directly call fclose without
         * validating whether the FD is part of the tracked set.
         */
-       if (URCU_TLS(ust_fd_mutex_nest))
+       if (URCU_TLS(thread_fd_tracking))
                return fclose_cb(stream);
 
        fd = fileno(stream);
@@ -447,7 +456,7 @@ int lttng_ust_safe_closefrom_fd(int lowfd, int (*close_cb)(int fd))
         * If called from lttng-ust, we directly call close without
         * validating whether the FD is part of the tracked set.
         */
-       if (URCU_TLS(ust_fd_mutex_nest)) {
+       if (URCU_TLS(thread_fd_tracking)) {
                for (i = lowfd; i < lttng_ust_max_fd; i++) {
                        if (close_cb(i) < 0) {
                                switch (errno) {
@@ -492,3 +501,8 @@ int lttng_ust_safe_closefrom_fd(int lowfd, int (*close_cb)(int fd))
 end:
        return ret;
 }
+
+void lttng_ust_fd_tracker_register_thread(void)
+{
+       URCU_TLS(thread_fd_tracking) = 1;
+}