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authorLinus Torvalds <torvalds@g5.osdl.org>2006-05-07 10:49:33 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-05-07 10:49:33 -0700
commitf5b40e363ad6041a96e3da32281d8faa191597b9 (patch)
tree5f35453cff7acd5df5622a108381bbd011a383c5 /kernel
parent5528e568a760442e0ec8fd2dea1f0791875a066b (diff)
Fix ptrace_attach()/ptrace_traceme()/de_thread() race
This holds the task lock (and, for ptrace_attach, the tasklist_lock) over the actual attach event, which closes a race between attacking to a thread that is either doing a PTRACE_TRACEME or getting de-threaded. Thanks to Oleg Nesterov for reminding me about this, and Chris Wright for noticing a lost return value in my first version. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/ptrace.c39
1 files changed, 21 insertions, 18 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 4e0f0ec003f7..b0f8da80d7d4 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -148,12 +148,16 @@ int ptrace_may_attach(struct task_struct *task)
int ptrace_attach(struct task_struct *task)
{
int retval;
- task_lock(task);
+
retval = -EPERM;
if (task->pid <= 1)
- goto bad;
+ goto out;
if (task->tgid == current->tgid)
- goto bad;
+ goto out;
+
+ write_lock_irq(&tasklist_lock);
+ task_lock(task);
+
/* the same process cannot be attached many times */
if (task->ptrace & PT_PTRACED)
goto bad;
@@ -166,17 +170,15 @@ int ptrace_attach(struct task_struct *task)
? PT_ATTACHED : 0);
if (capable(CAP_SYS_PTRACE))
task->ptrace |= PT_PTRACE_CAP;
- task_unlock(task);
- write_lock_irq(&tasklist_lock);
__ptrace_link(task, current);
- write_unlock_irq(&tasklist_lock);
force_sig_specific(SIGSTOP, task);
- return 0;
bad:
+ write_unlock_irq(&tasklist_lock);
task_unlock(task);
+out:
return retval;
}
@@ -417,21 +419,22 @@ int ptrace_request(struct task_struct *child, long request,
*/
int ptrace_traceme(void)
{
- int ret;
+ int ret = -EPERM;
/*
* Are we already being traced?
*/
- if (current->ptrace & PT_PTRACED)
- return -EPERM;
- ret = security_ptrace(current->parent, current);
- if (ret)
- return -EPERM;
- /*
- * Set the ptrace bit in the process ptrace flags.
- */
- current->ptrace |= PT_PTRACED;
- return 0;
+ task_lock(current);
+ if (!(current->ptrace & PT_PTRACED)) {
+ ret = security_ptrace(current->parent, current);
+ /*
+ * Set the ptrace bit in the process ptrace flags.
+ */
+ if (!ret)
+ current->ptrace |= PT_PTRACED;
+ }
+ task_unlock(current);
+ return ret;
}
/**