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ptrace: take into account saved_sigmask in PTRACE{GET,SET}SIGMASK

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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_GETSIGMASK returns saved_sigmask
if it's set.  PTRACE_SETSIGMASK drops the TIF_RESTORE_SIGMASK flag.

Link: http://lkml.kernel.org/r/20181120060616.6043-1-avagin@gmail.com
Fixes: 29000caecb ("ptrace: add ability to get/set signal-blocked mask")
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrei Vagin 2019-03-28 20:44:13 -07:00 committed by Linus Torvalds
parent eebf364806
commit fcfc2aa018
2 changed files with 31 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
include/linux/sched/signal.h
View File

@ -418,10 +418,20 @@ 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);
@ -439,6 +449,10 @@ 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;
@ -447,6 +461,10 @@ 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)

15
kernel/ptrace.c
View File

@ -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.
@ -924,18 +925,26 @@ 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;
@ -961,6 +970,8 @@ 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;
}