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

[Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx>]

From: James Morse <james.morse@xxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: James Morse <james.morse@xxxxxxx>

Yury:
Replace sigset_{to,from}_compat() with new {get,put}_compat_sigset()
Signed-off-by: Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx>
---
 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