net/rds: fix warn in rds_message_alloc_sgs

redundant copy_from_user in rds_sendmsg system call expose rds
to issue where rds_rdma_extra_size walk the rds iovec and and
calculate the number pf pages (sgs) it need to add to the tail of
rds message and later rds_cmsg_rdma_args copy the rds iovec again
and re calculate the same number and get different result causing
WARN_ON in rds_message_alloc_sgs.

fix this by doing the copy_from_user only once per rds_sendmsg
system call.

When issue occur the below dump is seen:

WARNING: CPU: 0 PID: 19789 at net/rds/message.c:316 rds_message_alloc_sgs+0x10c/0x160 net/rds/message.c:316
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 19789 Comm: syz-executor827 Not tainted 4.19.0-next-20181030+ #101
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x244/0x39d lib/dump_stack.c:113
 panic+0x2ad/0x55c kernel/panic.c:188
 __warn.cold.8+0x20/0x45 kernel/panic.c:540
 report_bug+0x254/0x2d0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
 do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
RIP: 0010:rds_message_alloc_sgs+0x10c/0x160 net/rds/message.c:316
Code: c0 74 04 3c 03 7e 6c 44 01 ab 78 01 00 00 e8 2b 9e 35 fa 4c 89 e0 48 83 c4 08 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 14 9e 35 fa <0f> 0b 31 ff 44 89 ee e8 18 9f 35 fa 45 85 ed 75 1b e8 fe 9d 35 fa
RSP: 0018:ffff8801c51b7460 EFLAGS: 00010293
RAX: ffff8801bc412080 RBX: ffff8801d7bf4040 RCX: ffffffff8749c9e6
RDX: 0000000000000000 RSI: ffffffff8749ca5c RDI: 0000000000000004
RBP: ffff8801c51b7490 R08: ffff8801bc412080 R09: ffffed003b5c5b67
R10: ffffed003b5c5b67 R11: ffff8801dae2db3b R12: 0000000000000000
R13: 000000000007165c R14: 000000000007165c R15: 0000000000000005
 rds_cmsg_rdma_args+0x82d/0x1510 net/rds/rdma.c:623
 rds_cmsg_send net/rds/send.c:971 [inline]
 rds_sendmsg+0x19a2/0x3180 net/rds/send.c:1273
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xd5/0x120 net/socket.c:632
 ___sys_sendmsg+0x7fd/0x930 net/socket.c:2117
 __sys_sendmsg+0x11d/0x280 net/socket.c:2155
 __do_sys_sendmsg net/socket.c:2164 [inline]
 __se_sys_sendmsg net/socket.c:2162 [inline]
 __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x44a859
Code: e8 dc e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 6b cb fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f1d4710ada8 EFLAGS: 00000297 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000006dcc28 RCX: 000000000044a859
RDX: 0000000000000000 RSI: 0000000020001600 RDI: 0000000000000003
RBP: 00000000006dcc20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 00000000006dcc2c
R13: 646e732f7665642f R14: 00007f1d4710b9c0 R15: 00000000006dcd2c
Kernel Offset: disabled
Rebooting in 86400 seconds..

Reported-by: syzbot+26de17458aeda9d305d8@syzkaller.appspotmail.com
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: shamir rabinovitch <shamir.rabinovitch@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/rds/rdma.c

@@ -517,9 +517,10 @@ static int rds_rdma_pages(struct rds_iovec iov[], int nr_iovecs)
 	return tot_pages;
 }
 
-int rds_rdma_extra_size(struct rds_rdma_args *args)
+int rds_rdma_extra_size(struct rds_rdma_args *args,
+			struct rds_iov_vector *iov)
 {
-	struct rds_iovec vec;
+	struct rds_iovec *vec;
 	struct rds_iovec __user *local_vec;
 	int tot_pages = 0;
 	unsigned int nr_pages;
@@ -530,13 +531,23 @@ int rds_rdma_extra_size(struct rds_rdma_args *args)
 	if (args->nr_local == 0)
 		return -EINVAL;
 
-	/* figure out the number of pages in the vector */
-	for (i = 0; i < args->nr_local; i++) {
-		if (copy_from_user(&vec, &local_vec[i],
+	iov->iov = kcalloc(args->nr_local,
+			   sizeof(struct rds_iovec),
+			   GFP_KERNEL);
+	if (!iov->iov)
+		return -ENOMEM;
+
+	vec = &iov->iov[0];
+
+	if (copy_from_user(vec, local_vec, args->nr_local *
 			   sizeof(struct rds_iovec)))
 		return -EFAULT;
+	iov->len = args->nr_local;
+
+	/* figure out the number of pages in the vector */
+	for (i = 0; i < args->nr_local; i++, vec++) {
 
-		nr_pages = rds_pages_in_vec(&vec);
+		nr_pages = rds_pages_in_vec(vec);
 		if (nr_pages == 0)
 			return -EINVAL;
 
@@ -558,15 +569,15 @@ int rds_rdma_extra_size(struct rds_rdma_args *args)
  * Extract all arguments and set up the rdma_op
  */
 int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
-			  struct cmsghdr *cmsg)
+		       struct cmsghdr *cmsg,
+		       struct rds_iov_vector *vec)
 {
 	struct rds_rdma_args *args;
 	struct rm_rdma_op *op = &rm->rdma;
 	int nr_pages;
 	unsigned int nr_bytes;
 	struct page **pages = NULL;
-	struct rds_iovec iovstack[UIO_FASTIOV], *iovs = iovstack;
-	int iov_size;
+	struct rds_iovec *iovs;
 	unsigned int i, j;
 	int ret = 0;
 
@@ -586,31 +597,23 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
 		goto out_ret;
 	}
 
-	/* Check whether to allocate the iovec area */
-	iov_size = args->nr_local * sizeof(struct rds_iovec);
-	if (args->nr_local > UIO_FASTIOV) {
-		iovs = sock_kmalloc(rds_rs_to_sk(rs), iov_size, GFP_KERNEL);
-		if (!iovs) {
-			ret = -ENOMEM;
+	if (vec->len != args->nr_local) {
+		ret = -EINVAL;
 		goto out_ret;
 	}
-	}
 
-	if (copy_from_user(iovs, (struct rds_iovec __user *)(unsigned long) args->local_vec_addr, iov_size)) {
-		ret = -EFAULT;
-		goto out;
-	}
+	iovs = vec->iov;
 
 	nr_pages = rds_rdma_pages(iovs, args->nr_local);
 	if (nr_pages < 0) {
 		ret = -EINVAL;
-		goto out;
+		goto out_ret;
 	}
 
 	pages = kcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL);
 	if (!pages) {
 		ret = -ENOMEM;
-		goto out;
+		goto out_ret;
 	}
 
 	op->op_write = !!(args->flags & RDS_RDMA_READWRITE);
@@ -623,7 +626,7 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
 	op->op_sg = rds_message_alloc_sgs(rm, nr_pages);
 	if (!op->op_sg) {
 		ret = -ENOMEM;
-		goto out;
+		goto out_pages;
 	}
 
 	if (op->op_notify || op->op_recverr) {
@@ -635,7 +638,7 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
 		op->op_notifier = kmalloc(sizeof(struct rds_notifier), GFP_KERNEL);
 		if (!op->op_notifier) {
 			ret = -ENOMEM;
-			goto out;
+			goto out_pages;
 		}
 		op->op_notifier->n_user_token = args->user_token;
 		op->op_notifier->n_status = RDS_RDMA_SUCCESS;
@@ -681,7 +684,7 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
 		 */
 		ret = rds_pin_pages(iov->addr, nr, pages, !op->op_write);
 		if (ret < 0)
-			goto out;
+			goto out_pages;
 		else
 			ret = 0;
 
@@ -714,13 +717,11 @@ int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
 				nr_bytes,
 				(unsigned int) args->remote_vec.bytes);
 		ret = -EINVAL;
-		goto out;
+		goto out_pages;
 	}
 	op->op_bytes = nr_bytes;
 
-out:
-	if (iovs != iovstack)
-		sock_kfree_s(rds_rs_to_sk(rs), iovs, iov_size);
+out_pages:
 	kfree(pages);
 out_ret:
 	if (ret)

net/rds/rds.h

@@ -386,6 +386,18 @@ static inline void rds_message_zcopy_queue_init(struct rds_msg_zcopy_queue *q)
 	INIT_LIST_HEAD(&q->zcookie_head);
 }
 
+struct rds_iov_vector {
+	struct rds_iovec *iov;
+	int               len;
+};
+
+struct rds_iov_vector_arr {
+	struct rds_iov_vector *vec;
+	int                    len;
+	int                    indx;
+	int                    incr;
+};
+
 struct rds_message {
 	refcount_t		m_refcount;
 	struct list_head	m_sock_item;
@@ -904,13 +916,13 @@ int rds_get_mr(struct rds_sock *rs, char __user *optval, int optlen);
 int rds_get_mr_for_dest(struct rds_sock *rs, char __user *optval, int optlen);
 int rds_free_mr(struct rds_sock *rs, char __user *optval, int optlen);
 void rds_rdma_drop_keys(struct rds_sock *rs);
-int rds_rdma_extra_size(struct rds_rdma_args *args);
-int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
-			  struct cmsghdr *cmsg);
+int rds_rdma_extra_size(struct rds_rdma_args *args,
+			struct rds_iov_vector *iov);
 int rds_cmsg_rdma_dest(struct rds_sock *rs, struct rds_message *rm,
 			  struct cmsghdr *cmsg);
 int rds_cmsg_rdma_args(struct rds_sock *rs, struct rds_message *rm,
-			  struct cmsghdr *cmsg);
+			  struct cmsghdr *cmsg,
+			  struct rds_iov_vector *vec);
 int rds_cmsg_rdma_map(struct rds_sock *rs, struct rds_message *rm,
 			  struct cmsghdr *cmsg);
 void rds_rdma_free_op(struct rm_rdma_op *ro);

net/rds/send.c

@@ -876,13 +876,15 @@ static int rds_send_queue_rm(struct rds_sock *rs, struct rds_connection *conn,
  * rds_message is getting to be quite complicated, and we'd like to allocate
  * it all in one go. This figures out how big it needs to be up front.
  */
-static int rds_rm_size(struct msghdr *msg, int num_sgs)
+static int rds_rm_size(struct msghdr *msg, int num_sgs,
+		       struct rds_iov_vector_arr *vct)
 {
 	struct cmsghdr *cmsg;
 	int size = 0;
 	int cmsg_groups = 0;
 	int retval;
 	bool zcopy_cookie = false;
+	struct rds_iov_vector *iov, *tmp_iov;
 
 	for_each_cmsghdr(cmsg, msg) {
 		if (!CMSG_OK(msg, cmsg))
@@ -893,8 +895,24 @@ static int rds_rm_size(struct msghdr *msg, int num_sgs)
 
 		switch (cmsg->cmsg_type) {
 		case RDS_CMSG_RDMA_ARGS:
+			if (vct->indx >= vct->len) {
+				vct->len += vct->incr;
+				tmp_iov =
+					krealloc(vct->vec,
+						 vct->len *
+						 sizeof(struct rds_iov_vector),
+						 GFP_KERNEL);
+				if (!tmp_iov) {
+					vct->len -= vct->incr;
+					return -ENOMEM;
+				}
+				vct->vec = tmp_iov;
+			}
+			iov = &vct->vec[vct->indx];
+			memset(iov, 0, sizeof(struct rds_iov_vector));
+			vct->indx++;
 			cmsg_groups |= 1;
-			retval = rds_rdma_extra_size(CMSG_DATA(cmsg));
+			retval = rds_rdma_extra_size(CMSG_DATA(cmsg), iov);
 			if (retval < 0)
 				return retval;
 			size += retval;
@@ -951,10 +969,11 @@ static int rds_cmsg_zcopy(struct rds_sock *rs, struct rds_message *rm,
 }
 
 static int rds_cmsg_send(struct rds_sock *rs, struct rds_message *rm,
-			 struct msghdr *msg, int *allocated_mr)
+			 struct msghdr *msg, int *allocated_mr,
+			 struct rds_iov_vector_arr *vct)
 {
 	struct cmsghdr *cmsg;
-	int ret = 0;
+	int ret = 0, ind = 0;
 
 	for_each_cmsghdr(cmsg, msg) {
 		if (!CMSG_OK(msg, cmsg))
@@ -968,7 +987,10 @@ static int rds_cmsg_send(struct rds_sock *rs, struct rds_message *rm,
 		 */
 		switch (cmsg->cmsg_type) {
 		case RDS_CMSG_RDMA_ARGS:
-			ret = rds_cmsg_rdma_args(rs, rm, cmsg);
+			if (ind >= vct->indx)
+				return -ENOMEM;
+			ret = rds_cmsg_rdma_args(rs, rm, cmsg, &vct->vec[ind]);
+			ind++;
 			break;
 
 		case RDS_CMSG_RDMA_DEST:
@@ -1084,6 +1106,11 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
 		      sock_flag(rds_rs_to_sk(rs), SOCK_ZEROCOPY));
 	int num_sgs = ceil(payload_len, PAGE_SIZE);
 	int namelen;
+	struct rds_iov_vector_arr vct = {0};
+	int ind;
+
+	/* expect 1 RDMA CMSG per rds_sendmsg. can still grow if more needed. */
+	vct.incr = 1;
 
 	/* Mirror Linux UDP mirror of BSD error message compatibility */
 	/* XXX: Perhaps MSG_MORE someday */
@@ -1220,7 +1247,7 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
 		num_sgs = iov_iter_npages(&msg->msg_iter, INT_MAX);
 	}
 	/* size of rm including all sgs */
-	ret = rds_rm_size(msg, num_sgs);
+	ret = rds_rm_size(msg, num_sgs, &vct);
 	if (ret < 0)
 		goto out;
 
@@ -1270,7 +1297,7 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
 	rm->m_conn_path = cpath;
 
 	/* Parse any control messages the user may have included. */
-	ret = rds_cmsg_send(rs, rm, msg, &allocated_mr);
+	ret = rds_cmsg_send(rs, rm, msg, &allocated_mr, &vct);
 	if (ret) {
 		/* Trigger connection so that its ready for the next retry */
 		if (ret ==  -EAGAIN)
@@ -1348,9 +1375,18 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len)
 	if (ret)
 		goto out;
 	rds_message_put(rm);
+
+	for (ind = 0; ind < vct.indx; ind++)
+		kfree(vct.vec[ind].iov);
+	kfree(vct.vec);
+
 	return payload_len;
 
 out:
+	for (ind = 0; ind < vct.indx; ind++)
+		kfree(vct.vec[ind].iov);
+	kfree(vct.vec);
+
 	/* If the user included a RDMA_MAP cmsg, we allocated a MR on the fly.
 	 * If the sendmsg goes through, we keep the MR. If it fails with EAGAIN
 	 * or in any other way, we need to destroy the MR again */