From 3043f16d66bf5a1d754bc34323d84d9a048c6cf4 Mon Sep 17 00:00:00 2001
From: Jan Beich <jbeich@FreeBSD.org>
Date: Mon, 28 Sep 2020 05:14:52 +0000
Subject: [PATCH] util: mimic KCMP_FILE via KERN_FILE on DragonFly and FreeBSD

Iterate over all file descriptors and compare their kernel addresses.

Reviewed-by: Emmanuel Vadot <manu@FreeBSD.org>
Reviewed-by: Val Packett <val@packett.cool>
---
 src/util/os_file.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/src/util/os_file.c b/src/util/os_file.c
index 5fb30f2d9084f..f3e1a1ff6f36f 100644
--- a/src/util/os_file.c
+++ b/src/util/os_file.c
@@ -214,6 +214,58 @@ os_same_file_description(int fd1, int fd2)
    return syscall(SYS_kcmp, pid, pid, KCMP_FILE, fd1, fd2);
 }
 
+#elif DETECT_OS_DRAGONFLY || DETECT_OS_FREEBSD
+
+#include "macros.h" /* ARRAY_SIZE */
+
+#include <sys/sysctl.h>
+#if DETECT_OS_DRAGONFLY
+#include <sys/kinfo.h>
+typedef void *kvaddr_t;
+#elif DETECT_OS_FREEBSD
+#include <sys/file.h>
+#define kinfo_file xfile
+#define f_pid xf_pid
+#define f_fd xf_fd
+#define f_file xf_file
+#endif
+
+int
+os_same_file_description(int fd1, int fd2)
+{
+   /* Same file descriptor trivially implies same file description */
+   if (fd1 == fd2)
+      return 0;
+
+   int mib[] = { CTL_KERN, KERN_FILE };
+   size_t len;
+   if (sysctl(mib, ARRAY_SIZE(mib), NULL, &len, NULL, 0))
+      return -1;
+   struct kinfo_file *kf = malloc(len);
+   if (sysctl(mib, ARRAY_SIZE(mib), kf, &len, NULL, 0))
+      return -1;
+
+   int count = len / sizeof(*kf);
+   pid_t pid = getpid();
+   kvaddr_t fd1_kfile = 0, fd2_kfile = 0;
+   for (int i = 0; i < count; i++) {
+      if (pid == kf[i].f_pid) {
+         if (fd1 == kf[i].f_fd) {
+            fd1_kfile = kf[i].f_file;
+         }
+         if (fd2 == kf[i].f_fd) {
+            fd2_kfile = kf[i].f_file;
+         }
+      }
+   }
+   free(kf);
+
+   if (fd1_kfile == 0 || fd2_kfile == 0)
+      return -1;
+
+   return (fd1_kfile < fd2_kfile) | ((fd1_kfile > fd2_kfile) << 1);
+}
+
 #else
 
 int
-- 
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