linux-kernel - [PATCH 3/6] ppoll: deduplicate compat logic

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Date:   Mon, 11 Jan 2021 19:30:14 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
        akpm@...ux-foundation.org, willy@...radead.org, arnd@...nel.org,
        Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH 3/6] ppoll: deduplicate compat logic

From: Willem de Bruijn <willemb@...gle.com>

Apply the same compat deduplication strategy to ppoll that was
previously applied to select and pselect.

Like pselect, ppoll has timespec and sigmask arguments, which have
compat variants. poll has neither, so is not modified.

Convert the ppoll syscall to a do_ppoll() helper that branches on
timespec and sigmask variants internally.

This allows calling the same implementation for all syscall variants:
standard, time32, compat, compat + time32.

Signed-off-by: Willem de Bruijn <willemb@...gle.com>
---
 fs/select.c | 91 ++++++++++++++++++-----------------------------------
 1 file changed, 30 insertions(+), 61 deletions(-)

diff --git a/fs/select.c b/fs/select.c
index dee7dfc5217b..27567795a892 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -1120,28 +1120,48 @@ SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
 	return ret;
 }
 
-SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
-		struct __kernel_timespec __user *, tsp, const sigset_t __user *, sigmask,
-		size_t, sigsetsize)
+static int do_ppoll(struct pollfd __user *ufds, unsigned int nfds,
+		    void __user *tsp, const void __user *sigmask,
+		    size_t sigsetsize, enum poll_time_type type)
 {
 	struct timespec64 ts, end_time, *to = NULL;
 	int ret;
 
 	if (tsp) {
-		if (get_timespec64(&ts, tsp))
-			return -EFAULT;
+		switch (type) {
+		case PT_TIMESPEC:
+			if (get_timespec64(&ts, tsp))
+				return -EFAULT;
+			break;
+		case PT_OLD_TIMESPEC:
+			if (get_old_timespec32(&ts, tsp))
+				return -EFAULT;
+			break;
+		default:
+			BUG();
+		}
 
 		to = &end_time;
 		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
 			return -EINVAL;
 	}
 
-	ret = set_user_sigmask(sigmask, sigsetsize);
+	if (!in_compat_syscall())
+		ret = set_user_sigmask(sigmask, sigsetsize);
+	else
+		ret = set_compat_user_sigmask(sigmask, sigsetsize);
 	if (ret)
 		return ret;
 
 	ret = do_sys_poll(ufds, nfds, to);
-	return poll_select_finish(&end_time, tsp, PT_TIMESPEC, ret);
+	return poll_select_finish(&end_time, tsp, type, ret);
+}
+
+SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
+		struct __kernel_timespec __user *, tsp, const sigset_t __user *, sigmask,
+		size_t, sigsetsize)
+{
+	return do_ppoll(ufds, nfds, tsp, sigmask, sigsetsize, PT_TIMESPEC);
 }
 
 #if defined(CONFIG_COMPAT_32BIT_TIME) && !defined(CONFIG_64BIT)
@@ -1150,24 +1170,7 @@ SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds, unsigned int, nfds,
 		struct old_timespec32 __user *, tsp, const sigset_t __user *, sigmask,
 		size_t, sigsetsize)
 {
-	struct timespec64 ts, end_time, *to = NULL;
-	int ret;
-
-	if (tsp) {
-		if (get_old_timespec32(&ts, tsp))
-			return -EFAULT;
-
-		to = &end_time;
-		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
-			return -EINVAL;
-	}
-
-	ret = set_user_sigmask(sigmask, sigsetsize);
-	if (ret)
-		return ret;
-
-	ret = do_sys_poll(ufds, nfds, to);
-	return poll_select_finish(&end_time, tsp, PT_OLD_TIMESPEC, ret);
+	return do_ppoll(ufds, nfds, tsp, sigmask, sigsetsize, PT_OLD_TIMESPEC);
 }
 #endif
 
@@ -1258,24 +1261,7 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time32, struct pollfd __user *, ufds,
 	unsigned int,  nfds, struct old_timespec32 __user *, tsp,
 	const compat_sigset_t __user *, sigmask, compat_size_t, sigsetsize)
 {
-	struct timespec64 ts, end_time, *to = NULL;
-	int ret;
-
-	if (tsp) {
-		if (get_old_timespec32(&ts, tsp))
-			return -EFAULT;
-
-		to = &end_time;
-		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
-			return -EINVAL;
-	}
-
-	ret = set_compat_user_sigmask(sigmask, sigsetsize);
-	if (ret)
-		return ret;
-
-	ret = do_sys_poll(ufds, nfds, to);
-	return poll_select_finish(&end_time, tsp, PT_OLD_TIMESPEC, ret);
+	return do_ppoll(ufds, nfds, tsp, sigmask, sigsetsize, PT_OLD_TIMESPEC);
 }
 #endif
 
@@ -1284,24 +1270,7 @@ COMPAT_SYSCALL_DEFINE5(ppoll_time64, struct pollfd __user *, ufds,
 	unsigned int,  nfds, struct __kernel_timespec __user *, tsp,
 	const compat_sigset_t __user *, sigmask, compat_size_t, sigsetsize)
 {
-	struct timespec64 ts, end_time, *to = NULL;
-	int ret;
-
-	if (tsp) {
-		if (get_timespec64(&ts, tsp))
-			return -EFAULT;
-
-		to = &end_time;
-		if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
-			return -EINVAL;
-	}
-
-	ret = set_compat_user_sigmask(sigmask, sigsetsize);
-	if (ret)
-		return ret;
-
-	ret = do_sys_poll(ufds, nfds, to);
-	return poll_select_finish(&end_time, tsp, PT_TIMESPEC, ret);
+	return do_ppoll(ufds, nfds, tsp, sigmask, sigsetsize, PT_TIMESPEC);
 }
 
 #endif
-- 
2.30.0.284.gd98b1dd5eaa7-goog