lkml.org 
[lkml]   [2010]   [Mar]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] ptrace: kill BKL in ptrace syscall
Date
From: Arnd Bergmann <arnd@arndb.de>

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>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
kernel/ptrace.c | 10 ----------
1 files changed, 0 insertions(+), 10 deletions(-)
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 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
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 @@ SYSCALL_DEFINE4(ptrace, long, request, long, pid, long, addr, long, data)
out_put_task_struct:
put_task_struct(child);
out:
- unlock_kernel();
return ret;
}

@@ -813,10 +808,6 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
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 @@ asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
out_put_task_struct:
put_task_struct(child);
out:
- unlock_kernel();
return ret;
}
#endif /* CONFIG_COMPAT */
--
1.6.2.3


\
 
 \ /
  Last update: 2010-03-28 23:41    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site