Merge branch 'get-rid-of-the-address_space-override-in-setsockopt-v2'

Christoph Hellwig says:

====================
get rid of the address_space override in setsockopt v2

setsockopt is the last place in architecture-independ code that still
uses set_fs to force the uaccess routines to operate on kernel pointers.

This series adds a new sockptr_t type that can contained either a kernel
or user pointer, and which has accessors that do the right thing, and
then uses it for setsockopt, starting by refactoring some low-level
helpers and moving them over to it before finally doing the main
setsockopt method.

Note that apparently the eBPF selftests do not even cover this path, so
the series has been tested with a testing patch that always copies the
data first and passes a kernel pointer.  This is something that works for
most common sockopts (and is something that the ePBF support relies on),
but unfortunately in various corner cases we either don't use the passed
in length, or in one case actually copy data back from setsockopt, or in
case of bpfilter straight out do not work with kernel pointers at all.

Against net-next/master.

Changes since v1:
 - check that users don't pass in kernel addresses
 - more bpfilter cleanups
 - cosmetic mptcp tweak
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

8 files changed, 153 insertions, 15 deletions

diff --git a/include/linux/bpfilter.h b/include/linux/bpfilter.h
index 9b114c718a76..2ae3c8e1d83c 100644
--- a/include/linux/bpfilter.h
+++ b/include/linux/bpfilter.h
@@ -4,9 +4,10 @@
 
 #include <uapi/linux/bpfilter.h>
 #include <linux/usermode_driver.h>
+#include <linux/sockptr.h>
 
 struct sock;
-int bpfilter_ip_set_sockopt(struct sock *sk, int optname, char __user *optval,
+int bpfilter_ip_set_sockopt(struct sock *sk, int optname, sockptr_t optval,
 			    unsigned int optlen);
 int bpfilter_ip_get_sockopt(struct sock *sk, int optname, char __user *optval,
 			    int __user *optlen);
@@ -16,8 +17,7 @@ struct bpfilter_umh_ops {
 	struct umd_info info;
 	/* since ip_getsockopt() can run in parallel, serialize access to umh */
 	struct mutex lock;
-	int (*sockopt)(struct sock *sk, int optname,
-		       char __user *optval,
+	int (*sockopt)(struct sock *sk, int optname, sockptr_t optval,
 		       unsigned int optlen, bool is_set);
 	int (*start)(void);
 };
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 1c6b6d982bf4..d07a6e973a7d 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -20,6 +20,7 @@
 #include <linux/kallsyms.h>
 #include <linux/if_vlan.h>
 #include <linux/vmalloc.h>
+#include <linux/sockptr.h>
 #include <crypto/sha.h>
 
 #include <net/sch_generic.h>
@@ -1276,7 +1277,7 @@ struct bpf_sockopt_kern {
 	s32		retval;
 };
 
-int copy_bpf_fprog_from_user(struct sock_fprog *dst, void __user *src, int len);
+int copy_bpf_fprog_from_user(struct sock_fprog *dst, sockptr_t src, int len);
 
 struct bpf_sk_lookup_kern {
 	u16		family;
diff --git a/include/linux/mroute.h b/include/linux/mroute.h
index 9a36fad9e068..6cbbfe94348c 100644
--- a/include/linux/mroute.h
+++ b/include/linux/mroute.h
@@ -8,6 +8,7 @@
 #include <net/fib_notifier.h>
 #include <uapi/linux/mroute.h>
 #include <linux/mroute_base.h>
+#include <linux/sockptr.h>
 
 #ifdef CONFIG_IP_MROUTE
 static inline int ip_mroute_opt(int opt)
@@ -15,7 +16,7 @@ static inline int ip_mroute_opt(int opt)
 	return opt >= MRT_BASE && opt <= MRT_MAX;
 }
 
-int ip_mroute_setsockopt(struct sock *, int, char __user *, unsigned int);
+int ip_mroute_setsockopt(struct sock *, int, sockptr_t, unsigned int);
 int ip_mroute_getsockopt(struct sock *, int, char __user *, int __user *);
 int ipmr_ioctl(struct sock *sk, int cmd, void __user *arg);
 int ipmr_compat_ioctl(struct sock *sk, unsigned int cmd, void __user *arg);
@@ -23,7 +24,7 @@ int ip_mr_init(void);
 bool ipmr_rule_default(const struct fib_rule *rule);
 #else
 static inline int ip_mroute_setsockopt(struct sock *sock, int optname,
-				       char __user *optval, unsigned int optlen)
+				       sockptr_t optval, unsigned int optlen)
 {
 	return -ENOPROTOOPT;
 }
diff --git a/include/linux/mroute6.h b/include/linux/mroute6.h
index c4a45859f586..bc351a85ce9b 100644
--- a/include/linux/mroute6.h
+++ b/include/linux/mroute6.h
@@ -8,6 +8,7 @@
 #include <net/net_namespace.h>
 #include <uapi/linux/mroute6.h>
 #include <linux/mroute_base.h>
+#include <linux/sockptr.h>
 #include <net/fib_rules.h>
 
 #ifdef CONFIG_IPV6_MROUTE
@@ -25,7 +26,7 @@ static inline int ip6_mroute_opt(int opt)
 struct sock;
 
 #ifdef CONFIG_IPV6_MROUTE
-extern int ip6_mroute_setsockopt(struct sock *, int, char __user *, unsigned int);
+extern int ip6_mroute_setsockopt(struct sock *, int, sockptr_t, unsigned int);
 extern int ip6_mroute_getsockopt(struct sock *, int, char __user *, int __user *);
 extern int ip6_mr_input(struct sk_buff *skb);
 extern int ip6mr_ioctl(struct sock *sk, int cmd, void __user *arg);
@@ -33,9 +34,8 @@ extern int ip6mr_compat_ioctl(struct sock *sk, unsigned int cmd, void __user *ar
 extern int ip6_mr_init(void);
 extern void ip6_mr_cleanup(void);
 #else
-static inline
-int ip6_mroute_setsockopt(struct sock *sock,
-			  int optname, char __user *optval, unsigned int optlen)
+static inline int ip6_mroute_setsockopt(struct sock *sock, int optname,
+		sockptr_t optval, unsigned int optlen)
 {
 	return -ENOPROTOOPT;
 }
diff --git a/include/linux/net.h b/include/linux/net.h
index 858ff1d98154..d48ff1180879 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -21,6 +21,7 @@
 #include <linux/rcupdate.h>
 #include <linux/once.h>
 #include <linux/fs.h>
+#include <linux/sockptr.h>
 
 #include <uapi/linux/net.h>
 
@@ -162,7 +163,8 @@ struct proto_ops {
 	int		(*listen)    (struct socket *sock, int len);
 	int		(*shutdown)  (struct socket *sock, int flags);
 	int		(*setsockopt)(struct socket *sock, int level,
-				      int optname, char __user *optval, unsigned int optlen);
+				      int optname, sockptr_t optval,
+				      unsigned int optlen);
 	int		(*getsockopt)(struct socket *sock, int level,
 				      int optname, char __user *optval, int __user *optlen);
 	void		(*show_fdinfo)(struct seq_file *m, struct socket *sock);
diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index 711b4d4486f0..0101747de549 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -13,6 +13,7 @@
 #include <linux/static_key.h>
 #include <linux/netfilter_defs.h>
 #include <linux/netdevice.h>
+#include <linux/sockptr.h>
 #include <net/net_namespace.h>
 
 static inline int NF_DROP_GETERR(int verdict)
@@ -163,7 +164,8 @@ struct nf_sockopt_ops {
 	/* Non-inclusive ranges: use 0/0/NULL to never get called. */
 	int set_optmin;
 	int set_optmax;
-	int (*set)(struct sock *sk, int optval, void __user *user, unsigned int len);
+	int (*set)(struct sock *sk, int optval, sockptr_t arg,
+		   unsigned int len);
 	int get_optmin;
 	int get_optmax;
 	int (*get)(struct sock *sk, int optval, void __user *user, int *len);
@@ -338,7 +340,7 @@ NF_HOOK_LIST(uint8_t pf, unsigned int hook, struct net *net, struct sock *sk,
 }
 
 /* Call setsockopt() */
-int nf_setsockopt(struct sock *sk, u_int8_t pf, int optval, char __user *opt,
+int nf_setsockopt(struct sock *sk, u_int8_t pf, int optval, sockptr_t opt,
 		  unsigned int len);
 int nf_getsockopt(struct sock *sk, u_int8_t pf, int optval, char __user *opt,
 		  int *len);
diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index b8b943ee7b8b..5deb099d156d 100644
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -301,8 +301,8 @@ int xt_target_to_user(const struct xt_entry_target *t,
 int xt_data_to_user(void __user *dst, const void *src,
 		    int usersize, int size, int aligned_size);
 
-void *xt_copy_counters_from_user(const void __user *user, unsigned int len,
-				 struct xt_counters_info *info);
+void *xt_copy_counters(sockptr_t arg, unsigned int len,
+		       struct xt_counters_info *info);
 struct xt_counters *xt_counters_alloc(unsigned int counters);
 
 struct xt_table *xt_register_table(struct net *net,
diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h
new file mode 100644
index 000000000000..7d5cdb2b30b5
--- /dev/null
+++ b/include/linux/sockptr.h
@@ -0,0 +1,132 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2020 Christoph Hellwig.
+ *
+ * Support for "universal" pointers that can point to either kernel or userspace
+ * memory.
+ */
+#ifndef _LINUX_SOCKPTR_H
+#define _LINUX_SOCKPTR_H
+
+#include <linux/compiler.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
+typedef union {
+	void		*kernel;
+	void __user	*user;
+} sockptr_t;
+
+static inline bool sockptr_is_kernel(sockptr_t sockptr)
+{
+	return (unsigned long)sockptr.kernel >= TASK_SIZE;
+}
+
+static inline sockptr_t KERNEL_SOCKPTR(void *p)
+{
+	return (sockptr_t) { .kernel = p };
+}
+
+static inline int __must_check init_user_sockptr(sockptr_t *sp, void __user *p)
+{
+	if ((unsigned long)p >= TASK_SIZE)
+		return -EFAULT;
+	sp->user = p;
+	return 0;
+}
+#else /* CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE */
+typedef struct {
+	union {
+		void		*kernel;
+		void __user	*user;
+	};
+	bool		is_kernel : 1;
+} sockptr_t;
+
+static inline bool sockptr_is_kernel(sockptr_t sockptr)
+{
+	return sockptr.is_kernel;
+}
+
+static inline sockptr_t KERNEL_SOCKPTR(void *p)
+{
+	return (sockptr_t) { .kernel = p, .is_kernel = true };
+}
+
+static inline int __must_check init_user_sockptr(sockptr_t *sp, void __user *p)
+{
+	sp->user = p;
+	sp->is_kernel = false;
+	return 0;
+}
+#endif /* CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE */
+
+static inline bool sockptr_is_null(sockptr_t sockptr)
+{
+	return !sockptr.user && !sockptr.kernel;
+}
+
+static inline int copy_from_sockptr(void *dst, sockptr_t src, size_t size)
+{
+	if (!sockptr_is_kernel(src))
+		return copy_from_user(dst, src.user, size);
+	memcpy(dst, src.kernel, size);
+	return 0;
+}
+
+static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size)
+{
+	if (!sockptr_is_kernel(dst))
+		return copy_to_user(dst.user, src, size);
+	memcpy(dst.kernel, src, size);
+	return 0;
+}
+
+static inline void *memdup_sockptr(sockptr_t src, size_t len)
+{
+	void *p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
+
+	if (!p)
+		return ERR_PTR(-ENOMEM);
+	if (copy_from_sockptr(p, src, len)) {
+		kfree(p);
+		return ERR_PTR(-EFAULT);
+	}
+	return p;
+}
+
+static inline void *memdup_sockptr_nul(sockptr_t src, size_t len)
+{
+	char *p = kmalloc_track_caller(len + 1, GFP_KERNEL);
+
+	if (!p)
+		return ERR_PTR(-ENOMEM);
+	if (copy_from_sockptr(p, src, len)) {
+		kfree(p);
+		return ERR_PTR(-EFAULT);
+	}
+	p[len] = '\0';
+	return p;
+}
+
+static inline void sockptr_advance(sockptr_t sockptr, size_t len)
+{
+	if (sockptr_is_kernel(sockptr))
+		sockptr.kernel += len;
+	else
+		sockptr.user += len;
+}
+
+static inline long strncpy_from_sockptr(char *dst, sockptr_t src, size_t count)
+{
+	if (sockptr_is_kernel(src)) {
+		size_t len = min(strnlen(src.kernel, count - 1) + 1, count);
+
+		memcpy(dst, src.kernel, len);
+		return len;
+	}
+	return strncpy_from_user(dst, src.user, count);
+}
+
+#endif /* _LINUX_SOCKPTR_H */