Subject: Re: [Bugme-new] [Bug 8342] New: sctp_getsockopt_local_addrs_old() calls copy_to_user() while a spinlock is held

From: Vlad Yasevich <[email-masked]>
Date: Thu, 26 Apr 2007 09:22:11 -0400

David Miller wrote:
> From: Vlad Yasevich <[email-masked]>
> Date: Mon, 23 Apr 2007 13:43:35 -0400
> 
>> [PATCH] [SCTP] Fix sctp_getsockopt_local_addrs_old() to use local storage
>>
>> sctp_getsockopt_local_addrs_old() in net/sctp/socket.c calls copy_to_user()
>> while the spinlock addr_lock is held. this should not be done as copy_to_user()
>> might sleep. the call to sctp_copy_laddrs_to_user() while holding the lock is
>> also problematic as it calls copy_to_user()
>>
>> Signed-off-by: Vlad Yasevich <[email-masked]>
> 
> As Andrew Morton just noticed and fixed in -mm, you're passing
> in int pointers to arguments that should be size_t pointers,
> specifically for some of the calls to sctp_copy_laddrs().
> 
> Please fix this, and please start testing builds on 64-bit
> platforms (even if via cross compile) so that you can catch
> these as the warnings generated by the compiler on this one
> were obvious.
> 

Sorry... I built and tested it on ia64, but the warning scrolled off the page.

Here is an updated patch.  bytes_copied got turned into an int everywhere since that
is what the new API expects, so it should be enough for the old api as well.  This also
makes the code more consistent.

-vlad

>>From 0df13de48d2c6cb27ee5a73ebd8dff85eb88d1f1 Mon Sep 17 00:00:00 2001
From: Vlad Yasevich <[email-masked]>
Date: Mon, 23 Apr 2007 13:41:05 -0400
Subject: [PATCH] [SCTP] Fix sctp_getsockopt_local_addrs_old() to use local storage

sctp_getsockopt_local_addrs_old() in net/sctp/socket.c calls copy_to_user()
while the spinlock addr_lock is held. this should not be done as copy_to_user()
might sleep. the call to sctp_copy_laddrs_to_user() while holding the lock is
also problematic as it calls copy_to_user()

Signed-off-by: Vlad Yasevich <[email-masked]>
---
 net/sctp/socket.c |   96 +++++++++++++++++++++++++++++++++--------------------
 1 files changed, 60 insertions(+), 36 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 6bfae12..e1a91b9 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -3849,7 +3849,7 @@ static int sctp_getsockopt_peer_addrs(struct sock *sk, int len,
 		memcpy(&temp, &from->ipaddr, sizeof(temp));
 		sctp_get_pf_specific(sk->sk_family)->addr_v4map(sp, &temp);
 		addrlen = sctp_get_af_specific(sk->sk_family)->sockaddr_len;
-		if(space_left < addrlen)
+		if (space_left < addrlen)
 			return -ENOMEM;
 		if (copy_to_user(to, &temp, addrlen))
 			return -EFAULT;
@@ -3938,8 +3938,9 @@ done:
 /* Helper function that copies local addresses to user and returns the number
  * of addresses copied.
  */
-static int sctp_copy_laddrs_to_user_old(struct sock *sk, __u16 port, int max_addrs,
-					void __user *to)
+static int sctp_copy_laddrs_old(struct sock *sk, __u16 port,
+					int max_addrs, void *to,
+					int *bytes_copied)
 {
 	struct list_head *pos, *next;
 	struct sctp_sockaddr_entry *addr;
@@ -3956,10 +3957,10 @@ static int sctp_copy_laddrs_to_user_old(struct sock *sk, __u16 port, int max_add
 		sctp_get_pf_specific(sk->sk_family)->addr_v4map(sctp_sk(sk),
 								&temp);
 		addrlen = sctp_get_af_specific(temp.sa.sa_family)->sockaddr_len;
-		if (copy_to_user(to, &temp, addrlen))
-			return -EFAULT;
+		memcpy(to, &temp, addrlen);
 
 		to += addrlen;
+		*bytes_copied += addrlen;
 		cnt ++;
 		if (cnt >= max_addrs) break;
 	}
@@ -3967,8 +3968,8 @@ static int sctp_copy_laddrs_to_user_old(struct sock *sk, __u16 port, int max_add
 	return cnt;
 }
 
-static int sctp_copy_laddrs_to_user(struct sock *sk, __u16 port,
-				    void __user **to, size_t space_left)
+static int sctp_copy_laddrs(struct sock *sk, __u16 port, void *to,
+			    size_t space_left, int *bytes_copied)
 {
 	struct list_head *pos, *next;
 	struct sctp_sockaddr_entry *addr;
@@ -3985,14 +3986,14 @@ static int sctp_copy_laddrs_to_user(struct sock *sk, __u16 port,
 		sctp_get_pf_specific(sk->sk_family)->addr_v4map(sctp_sk(sk),
 								&temp);
 		addrlen = sctp_get_af_specific(temp.sa.sa_family)->sockaddr_len;
-		if(space_left<addrlen)
+		if (space_left < addrlen)
 			return -ENOMEM;
-		if (copy_to_user(*to, &temp, addrlen))
-			return -EFAULT;
+		memcpy(to, &temp, addrlen);
 
-		*to += addrlen;
+		to += addrlen;
 		cnt ++;
 		space_left -= addrlen;
+		bytes_copied += addrlen;
 	}
 
 	return cnt;
@@ -4016,6 +4017,8 @@ static int sctp_getsockopt_local_addrs_old(struct sock *sk, int len,
 	int addrlen;
 	rwlock_t *addr_lock;
 	int err = 0;
+	void *addrs;
+	int bytes_copied = 0;
 
 	if (len != sizeof(struct sctp_getaddrs_old))
 		return -EINVAL;
@@ -4043,6 +4046,15 @@ static int sctp_getsockopt_local_addrs_old(struct sock *sk, int len,
 
 	to = getaddrs.addrs;
 
+	/* Allocate space for a local instance of packed array to hold all
+	 * the data.  We store addresses here first and then put write them
+	 * to the user in one shot.
+	 */
+	addrs = kmalloc(sizeof(union sctp_addr) * getaddrs.addr_num,
+			GFP_KERNEL);
+	if (!addrs)
+		return -ENOMEM;
+
 	sctp_read_lock(addr_lock);
 
 	/* If the endpoint is bound to 0.0.0.0 or ::0, get the valid
@@ -4052,13 +4064,9 @@ static int sctp_getsockopt_local_addrs_old(struct sock *sk, int len,
 		addr = list_entry(bp->address_list.next,
 				  struct sctp_sockaddr_entry, list);
 		if (sctp_is_any(&addr->a)) {
-			cnt = sctp_copy_laddrs_to_user_old(sk, bp->port,
-							   getaddrs.addr_num,
-							   to);
-			if (cnt < 0) {
-				err = cnt;
-				goto unlock;
-			}
+			cnt = sctp_copy_laddrs_old(sk, bp->port,
+						   getaddrs.addr_num,
+						   addrs, &bytes_copied);
 			goto copy_getaddrs;
 		}
 	}
@@ -4068,22 +4076,29 @@ static int sctp_getsockopt_local_addrs_old(struct sock *sk, int len,
 		memcpy(&temp, &addr->a, sizeof(temp));
 		sctp_get_pf_specific(sk->sk_family)->addr_v4map(sp, &temp);
 		addrlen = sctp_get_af_specific(temp.sa.sa_family)->sockaddr_len;
-		if (copy_to_user(to, &temp, addrlen)) {
-			err = -EFAULT;
-			goto unlock;
-		}
+		memcpy(addrs, &temp, addrlen);
 		to += addrlen;
+		bytes_copied += addrlen;
 		cnt ++;
 		if (cnt >= getaddrs.addr_num) break;
 	}
 
 copy_getaddrs:
+	sctp_read_unlock(addr_lock);
+
+	/* copy the entire address list into the user provided space */
+	if (copy_to_user(to, addrs, bytes_copied)) {
+		err = -EFAULT;
+		goto error;
+	}
+
+	/* copy the leading structure back to user */
 	getaddrs.addr_num = cnt;
 	if (copy_to_user(optval, &getaddrs, sizeof(struct sctp_getaddrs_old)))
 		err = -EFAULT;
 
-unlock:
-	sctp_read_unlock(addr_lock);
+error:
+	kfree(addrs);
 	return err;
 }
 
@@ -4103,7 +4118,8 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 	rwlock_t *addr_lock;
 	int err = 0;
 	size_t space_left;
-	int bytes_copied;
+	int bytes_copied = 0;
+	void *addrs;
 
 	if (len <= sizeof(struct sctp_getaddrs))
 		return -EINVAL;
@@ -4131,6 +4147,9 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 	to = optval + offsetof(struct sctp_getaddrs,addrs);
 	space_left = len - sizeof(struct sctp_getaddrs) -
 			 offsetof(struct sctp_getaddrs,addrs);
+	addrs = kmalloc(space_left, GFP_KERNEL);
+	if (!addrs)
+		return -ENOMEM;
 
 	sctp_read_lock(addr_lock);
 
@@ -4141,11 +4160,11 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 		addr = list_entry(bp->address_list.next,
 				  struct sctp_sockaddr_entry, list);
 		if (sctp_is_any(&addr->a)) {
-			cnt = sctp_copy_laddrs_to_user(sk, bp->port,
-						       &to, space_left);
+			cnt = sctp_copy_laddrs(sk, bp->port, addrs,
+						space_left, &bytes_copied);
 			if (cnt < 0) {
 				err = cnt;
-				goto unlock;
+				goto error;
 			}
 			goto copy_getaddrs;
 		}
@@ -4156,26 +4175,31 @@ static int sctp_getsockopt_local_addrs(struct sock *sk, int len,
 		memcpy(&temp, &addr->a, sizeof(temp));
 		sctp_get_pf_specific(sk->sk_family)->addr_v4map(sp, &temp);
 		addrlen = sctp_get_af_specific(temp.sa.sa_family)->sockaddr_len;
-		if(space_left < addrlen)
-			return -ENOMEM; /*fixme: right error?*/
-		if (copy_to_user(to, &temp, addrlen)) {
-			err = -EFAULT;
-			goto unlock;
+		if (space_left < addrlen) {
+			err =  -ENOMEM; /*fixme: right error?*/
+			goto error;
 		}
+		memcpy(addrs, &temp, addrlen);
 		to += addrlen;
+		bytes_copied += addrlen;
 		cnt ++;
 		space_left -= addrlen;
 	}
 
 copy_getaddrs:
+	sctp_read_unlock(addr_lock);
+
+	if (copy_to_user(to, addrs, bytes_copied)) {
+		err = -EFAULT;
+		goto error;
+	}
 	if (put_user(cnt, &((struct sctp_getaddrs __user *)optval)->addr_num))
 		return -EFAULT;
-	bytes_copied = ((char __user *)to) - optval;
 	if (put_user(bytes_copied, optlen))
 		return -EFAULT;
 
-unlock:
-	sctp_read_unlock(addr_lock);
+error:
+	kfree(addrs);
 	return err;
 }
 
-- 
1.5.0.3.438.gc49b2