exec: introduce exec_binprm() for "depth == 0" code

task_pid_nr_ns() and trace/ptrace code in the middle of the recursive
search_binary_handler() looks confusing and imho annoying.  We only need
this code if "depth == 0", lets add a simple helper which calls
search_binary_handler() and does trace_sched_process_exec() +
ptrace_event().

The patch also moves the setting of task->did_exec, we need to do this
only once.

Note: we can kill either task->did_exec or PF_FORKNOEXEC.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Zach Levis <zml@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/exec.c b/fs/exec.c
index 2d1e52a..4d95b47 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1373,7 +1373,6 @@ int search_binary_handler(struct linux_binprm *bprm)
        unsigned int depth = bprm->recursion_depth;
        int try,retval;
        struct linux_binfmt *fmt;
-       pid_t old_pid, old_vpid;
 
        /* This allows 4 levels of binfmt rewrites before failing hard. */
        if (depth > 5)
@@ -1387,12 +1386,6 @@ int search_binary_handler(struct linux_binprm *bprm)
        if (retval)
                return retval;
 
-       /* Need to fetch pid before load_binary changes it */
-       old_pid = current->pid;
-       rcu_read_lock();
-       old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
-       rcu_read_unlock();
-
        retval = -ENOENT;
        for (try=0; try<2; try++) {
                read_lock(&binfmt_lock);
@@ -1407,16 +1400,11 @@ int search_binary_handler(struct linux_binprm *bprm)
                        retval = fn(bprm);
                        bprm->recursion_depth = depth;
                        if (retval >= 0) {
-                               if (depth == 0) {
-                                       trace_sched_process_exec(current, old_pid, bprm);
-                                       ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
-                               }
                                put_binfmt(fmt);
                                allow_write_access(bprm->file);
                                if (bprm->file)
                                        fput(bprm->file);
                                bprm->file = NULL;
-                               current->did_exec = 1;
                                proc_exec_connector(current);
                                return retval;
                        }
@@ -1450,9 +1438,29 @@ int search_binary_handler(struct linux_binprm *bprm)
        }
        return retval;
 }
-
 EXPORT_SYMBOL(search_binary_handler);
 
+static int exec_binprm(struct linux_binprm *bprm)
+{
+       pid_t old_pid, old_vpid;
+       int ret;
+
+       /* Need to fetch pid before load_binary changes it */
+       old_pid = current->pid;
+       rcu_read_lock();
+       old_vpid = task_pid_nr_ns(current, task_active_pid_ns(current->parent));
+       rcu_read_unlock();
+
+       ret = search_binary_handler(bprm);
+       if (ret >= 0) {
+               trace_sched_process_exec(current, old_pid, bprm);
+               ptrace_event(PTRACE_EVENT_EXEC, old_vpid);
+               current->did_exec = 1;
+       }
+
+       return ret;
+}
+
 /*
  * sys_execve() executes a new program.
  */
@@ -1541,7 +1549,7 @@ static int do_execve_common(const char *filename,
        if (retval < 0)
                goto out;
 
-       retval = search_binary_handler(bprm);
+       retval = exec_binprm(bprm);
        if (retval < 0)
                goto out;