MDEV-30815 Printing a stack trace leaks file descriptors.

	In situations where mariadbd emits a lot of stack traces it can
        run out of file descriptors. Each time the pipe to the external
        utility addr2line is opened, those file descriptor are never closed.

include/my_stacktrace.h

@@ -75,7 +75,8 @@ typedef struct {
 
 #ifdef HAVE_MY_ADDR_RESOLVE
 int my_addr_resolve(void *ptr, my_addr_loc *loc);
-const char *my_addr_resolve_init();
+const char *my_addr_resolve_init(void *ptr);
+void my_addr_resolve_close();
 #else
 #define my_addr_resolve_init()  (0)
 #define my_addr_resolve(A,B)    (1)

mysys/my_addr_resolve.c

@@ -115,7 +115,7 @@ int my_addr_resolve(void *ptr, my_addr_loc *loc)
   return 1;
 }
 
-const char *my_addr_resolve_init()
+const char *my_addr_resolve_init(void *ptr)
 {
   if (!bfdh)
   {
@@ -145,6 +145,11 @@ const char *my_addr_resolve_init()
 err:
   return bfd_errmsg(bfd_get_error());
 }
+
+
+void my_addr_resolve_close()
+{
+}
 #elif defined(HAVE_LIBELF_H)
 /*
   another possible implementation.
@@ -171,19 +176,11 @@ static char addr2line_binary[1024];
 static char output[1024];
 static struct pollfd poll_fds;
 static void *addr_offset;
+Dl_info info;
+
 
 int start_addr2line_fork(const char *binary_path)
 {
-
-  if (pid > 0)
-  {
-    /* Don't leak FDs */
-    close(in[1]);
-    close(out[0]);
-    /* Don't create zombie processes. */
-    waitpid(pid, NULL, 0);
-  }
-
   if (pipe(in) < 0)
     return 1;
   if (pipe(out) < 0)
@@ -211,6 +208,16 @@ int start_addr2line_fork(const char *binary_path)
   return 0;
 }
 
+
+void my_addr_resolve_close()
+{
+  /* Don't leak FDs */
+  close(in[1]);
+  close(out[0]);
+  /* Don't create zombie processes. */
+  waitpid(pid, NULL, 0);
+}
+
 static int first_error= 0;
 
 static int addr_resolve(void *ptr, my_addr_loc *loc)
@@ -297,25 +304,40 @@ static int addr_resolve(void *ptr, my_addr_loc *loc)
 
 int my_addr_resolve(void *ptr, my_addr_loc *loc)
 {
-  Dl_info info;
+#ifndef __PIE__
+  addr_offset= (void*) info.dli_fbase;
+  if (strcmp(info.dli_fname, my_progname) == 0 &&
+      addr_resolve((void*) my_addr_resolve, loc) == 0 &&
+      strcmp(loc->func, "my_addr_resolve") == 0)
+    addr_offset= 0;
+#endif
+
+  return addr_resolve((void*) (ptr - addr_offset), loc);
+}
+
 
+const char *my_addr_resolve_init(void *ptr)
+{
   if (!dladdr(ptr, &info))
-    return 1;
+    return "dladdr() error";
 
-  if (strcmp(addr2line_binary, info.dli_fname))
-  {
   /*
     We use dli_fname in case the path is longer than the length of
     our static string. We don't want to allocate anything
     dynamically here as we are in a "crashed" state.
     */
+
   if (start_addr2line_fork(info.dli_fname))
   {
     if (!first_error++)
+    {
       fputs("Can't start addr2line\n", stderr);
+      my_addr_resolve_close();
+    }
     addr2line_binary[0] = '\0';
-      return 2;
+    return "fork() error";
   }
+
   /* Save result for future comparisons. */
   strnmov(addr2line_binary, info.dli_fname, sizeof(addr2line_binary));
 
@@ -325,20 +347,7 @@ int my_addr_resolve(void *ptr, my_addr_loc *loc)
     done with PIE or not.
   */
   addr_offset= (void*) info.dli_fbase;
-#ifndef __PIE__
-    if (strcmp(info.dli_fname, my_progname) == 0 &&
-        addr_resolve((void*) my_addr_resolve, loc) == 0 &&
-	strcmp(loc->func, "my_addr_resolve") == 0)
-      addr_offset= 0;
-#endif
-  }
-
-  return addr_resolve((void*) (ptr - addr_offset), loc);
-}
-
 
-const char *my_addr_resolve_init()
-{
   return 0;
 }
 #endif

mysys/safemalloc.c

@@ -225,7 +225,7 @@ static void print_stack(void **frame)
   const char *err;
   int i;
 
-  if ((err= my_addr_resolve_init()))
+  if ((err= my_addr_resolve_init(frame[0])))
   {
     fprintf(stderr, "(my_addr_resolve failure: %s)\n", err);
     return;
@@ -243,6 +243,7 @@ static void print_stack(void **frame)
       fprintf(stderr, "%s:%u", loc.file, loc.line);
   }
   fprintf(stderr, "\n");
+  my_addr_resolve_close();
 }
 #else
 #define print_stack(X)          fprintf(stderr, "???\n")

mysys/stacktrace.c

@@ -185,7 +185,7 @@ static int print_with_addr_resolve(void **addrs, int n)
   int i;
   const char *err;
 
-  if ((err= my_addr_resolve_init()))
+  if ((err= my_addr_resolve_init(addrs[0])))
   {
     my_safe_printf_stderr("(my_addr_resolve failure: %s)\n", err);
     return 0;
@@ -200,6 +200,7 @@ static int print_with_addr_resolve(void **addrs, int n)
       my_safe_printf_stderr("%s:%u(%s)[%p]\n",
               loc.file, loc.line, loc.func, addrs[i]);
   }
+  my_addr_resolve_close();
   return 1;
 }
 #endif