[PATCH 02/24] ptrace: Add compat PTRACE_{G,S}ETSIGMASK handlers

Yury Norov
2018-05-16T08:18:47Z

From: James Morse <james.morse@arm.com>

compat_ptrace_request() lacks handlers for PTRACE_{G,S}ETSIGMASK,
instead using those in ptrace_request(). The compat variant should
read a compat_sigset_t from userspace instead of ptrace_request()s
sigset_t.

While compat_sigset_t is the same size as sigset_t, it is defined as
2xu32, instead of a single u64. On a big-endian CPU this means that
compat_sigset_t is passed to user-space using middle-endianness,
where the least-significant u32 is written most significant byte
first.

If ptrace_request()s code is used userspace will read the most
significant u32 where it expected the least significant.

Instead of duplicating ptrace_request()s code as a special case in
the arch code, handle it here.

Fixes: 29000caecbe87 ("ptrace: add ability to get/set signal-blocked mask")
CC: Andrey Vagin <avagin@openvz.org>
Signed-off-by: James Morse <james.morse@arm.com>

Yury:
Replace sigset_{to,from}_compat() with new {get,put}_compat_sigset()
Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
---
kernel/ptrace.c | 48 ++++++++++++++++++++++++++++++++++++------------
1 file changed, 36 insertions(+), 12 deletions(-)

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 21fec73d45d4..214944d7c268 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -880,6 +880,22 @@ static int ptrace_regset(struct task_struct *task, int req, unsigned int type,
EXPORT_SYMBOL_GPL(task_user_regset_view);
#endif

+static int ptrace_setsigmask(struct task_struct *child, sigset_t *new_set)
+{
+ sigdelsetmask(new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
+
+ /*
+ * Every thread does recalc_sigpending() after resume, so
+ * retarget_shared_pending() and recalc_sigpending() are not
+ * called here.
+ */
+ spin_lock_irq(&child->sighand->siglock);
+ child->blocked = *new_set;
+ spin_unlock_irq(&child->sighand->siglock);
+
+ return 0;
+}
+
int ptrace_request(struct task_struct *child, long request,
unsigned long addr, unsigned long data)
{
@@ -951,18 +967,7 @@ int ptrace_request(struct task_struct *child, long request,
break;
}

- sigdelsetmask(&new_set, sigmask(SIGKILL)|sigmask(SIGSTOP));
-
- /*
- * Every thread does recalc_sigpending() after resume, so
- * retarget_shared_pending() and recalc_sigpending() are not
- * called here.
- */
- spin_lock_irq(&child->sighand->siglock);
- child->blocked = new_set;
- spin_unlock_irq(&child->sighand->siglock);
-
- ret = 0;
+ ret = ptrace_setsigmask(child, &new_set);
break;
}

@@ -1181,6 +1186,7 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request,
{
compat_ulong_t __user *datap = compat_ptr(data);
compat_ulong_t word;
+ sigset_t new_set;
siginfo_t siginfo;
int ret;

@@ -1221,6 +1227,24 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request,
else
ret = ptrace_setsiginfo(child, &siginfo);
break;
+ case PTRACE_GETSIGMASK:
+ if (addr != sizeof(compat_sigset_t))
+ return -EINVAL;
+
+ ret = put_compat_sigset((compat_sigset_t __user *) datap,
+ &child->blocked, sizeof(compat_sigset_t));
+ break;
+ case PTRACE_SETSIGMASK:
+ if (addr != sizeof(compat_sigset_t))
+ return -EINVAL;
+
+ ret = get_compat_sigset(&new_set,
+ (compat_sigset_t __user *) datap);
+ if (ret)
+ break;
+
+ ret = ptrace_setsigmask(child, &new_set);
+ break;
#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
case PTRACE_GETREGSET:
case PTRACE_SETREGSET:
--
2.17.0