lkml.org 
[lkml]   [2018]   [Nov]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] ptrace: take into account saved_sigmask in PTRACE_{GET,SET}SIGMASK
Date
There are a few system calls (pselect, ppoll, etc) which replace a task
sigmask while they are running in a kernel-space

When a task calls one of these syscalls, the kernel saves a current
sigmask in task->saved_sigmask and sets a syscall sigmask.

On syscall-exit-stop, ptrace traps a task before restoring the
saved_sigmask, so PTRACE_GETSIGMASK returns the syscall sigmask and
PTRACE_SETSIGMASK does nothing, because its sigmask is replaced by
saved_sigmask, when the task returns to user-space.

This patch fixes this problem. PTRACE_GET_SIGMASK returns saved_sigmask
is it's set. PTRACE_SETSIGMASK drops the TIF_RESTORE_SIGMASK flag.

Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 29000caecbe8 ("ptrace: add ability to get/set signal-blocked mask")
Signed-off-by: Andrei Vagin <avagin@gmail.com>
---
include/linux/sched/signal.h | 18 ++++++++++++++++++
kernel/ptrace.c | 15 +++++++++++++--
2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 1be35729c2c5..660d78c9af6c 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -417,10 +417,20 @@ static inline void set_restore_sigmask(void)
set_thread_flag(TIF_RESTORE_SIGMASK);
WARN_ON(!test_thread_flag(TIF_SIGPENDING));
}
+
+static inline void clear_tsk_restore_sigmask(struct task_struct *tsk)
+{
+ clear_tsk_thread_flag(tsk, TIF_RESTORE_SIGMASK);
+}
+
static inline void clear_restore_sigmask(void)
{
clear_thread_flag(TIF_RESTORE_SIGMASK);
}
+static inline bool test_tsk_restore_sigmask(struct task_struct *tsk)
+{
+ return test_tsk_thread_flag(tsk, TIF_RESTORE_SIGMASK);
+}
static inline bool test_restore_sigmask(void)
{
return test_thread_flag(TIF_RESTORE_SIGMASK);
@@ -438,6 +448,10 @@ static inline void set_restore_sigmask(void)
current->restore_sigmask = true;
WARN_ON(!test_thread_flag(TIF_SIGPENDING));
}
+static inline void clear_tsk_restore_sigmask(struct task_struct *tsk)
+{
+ tsk->restore_sigmask = false;
+}
static inline void clear_restore_sigmask(void)
{
current->restore_sigmask = false;
@@ -446,6 +460,10 @@ static inline bool test_restore_sigmask(void)
{
return current->restore_sigmask;
}
+static inline bool test_tsk_restore_sigmask(struct task_struct *tsk)
+{
+ return tsk->restore_sigmask;
+}
static inline bool test_and_clear_restore_sigmask(void)
{
if (!current->restore_sigmask)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 21fec73d45d4..fc0d667f5792 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -29,6 +29,7 @@
#include <linux/hw_breakpoint.h>
#include <linux/cn_proc.h>
#include <linux/compat.h>
+#include <linux/sched/signal.h>

/*
* Access another process' address space via ptrace.
@@ -925,18 +926,26 @@ int ptrace_request(struct task_struct *child, long request,
ret = ptrace_setsiginfo(child, &siginfo);
break;

- case PTRACE_GETSIGMASK:
+ case PTRACE_GETSIGMASK: {
+ sigset_t *mask;
+
if (addr != sizeof(sigset_t)) {
ret = -EINVAL;
break;
}

- if (copy_to_user(datavp, &child->blocked, sizeof(sigset_t)))
+ if (test_tsk_restore_sigmask(child))
+ mask = &child->saved_sigmask;
+ else
+ mask = &child->blocked;
+
+ if (copy_to_user(datavp, mask, sizeof(sigset_t)))
ret = -EFAULT;
else
ret = 0;

break;
+ }

case PTRACE_SETSIGMASK: {
sigset_t new_set;
@@ -962,6 +971,8 @@ int ptrace_request(struct task_struct *child, long request,
child->blocked = new_set;
spin_unlock_irq(&child->sighand->siglock);

+ clear_tsk_restore_sigmask(child);
+
ret = 0;
break;
}
--
2.17.2
\
 
 \ /
  Last update: 2018-11-20 07:06    [W:0.157 / U:5.316 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site