ptrace: kill BKL in ptrace syscall
The comment suggests that this usage is stale. There is no bkl in the
exec path so if there is a race lurking there, the bkl in ptrace is
not going to help in this regard.
Overview of the possibility of "accidental" races this bkl might
protect:
- ptrace_traceme() is protected against task removal and concurrent
read/write on current->ptrace as it locks write tasklist_lock.
- arch_ptrace_attach() is serialized by ptrace_traceme() against
concurrent PTRACE_TRACEME or PTRACE_ATTACH
- ptrace_attach() is protected the same way ptrace_traceme() and
in turn serializes arch_ptrace_attach()
- ptrace_check_attach() does its own well described serializing too.
There is no obvious race here.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Roland McGrath <roland@redhat.com>
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 42ad8ae..5357502 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -666,10 +666,6 @@
struct task_struct *child;
long ret;
- /*
- * This lock_kernel fixes a subtle race with suid exec
- */
- lock_kernel();
if (request == PTRACE_TRACEME) {
ret = ptrace_traceme();
if (!ret)
@@ -703,7 +699,6 @@
out_put_task_struct:
put_task_struct(child);
out:
- unlock_kernel();
return ret;
}
@@ -813,10 +808,6 @@
struct task_struct *child;
long ret;
- /*
- * This lock_kernel fixes a subtle race with suid exec
- */
- lock_kernel();
if (request == PTRACE_TRACEME) {
ret = ptrace_traceme();
goto out;
@@ -846,7 +837,6 @@
out_put_task_struct:
put_task_struct(child);
out:
- unlock_kernel();
return ret;
}
#endif /* CONFIG_COMPAT */