Revert "Merge branch 'mctp-i2c-driver'"

This reverts commit 71812af7234f30362b43ccff33f93890ae4c0655, reversing
changes made to cc0be1ad686fb29a4d127948486f40b17fb34b50.

Wolfram Sang says:

Please revert. Besides the driver in net, it modifies the I2C core
code. This has not been acked by the I2C maintainer (in this case me).
So, please don't pull this in via the net tree. The question raised here
(extending SMBus calls to 255 byte) is complicated because we need ABI
backwards compatibility.

Link: https://lore.kernel.org/all/YZJ9H4eM%2FM7OXVN0@shikoro/
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 14 insertions, 79 deletions

diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index 5ee9118c04076..bce0e8bb78520 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -46,24 +46,6 @@ struct i2c_dev {
 	struct cdev cdev;
 };
 
-/* The userspace union i2c_smbus_data for I2C_SMBUS ioctl is limited
- * to 32 bytes (I2C_SMBUS_BLOCK_MAX) for compatibility.
- */
-union compat_i2c_smbus_data {
-	__u8 byte;
-	__u16 word;
-	__u8 block[I2C_SMBUS_BLOCK_MAX + 2]; /* block[0] is used for length */
-			       /* and one more for user-space compatibility */
-};
-
-/* Must match i2c-dev.h definition with compat .data member */
-struct i2c_smbus_ioctl_data {
-	__u8 read_write;
-	__u8 command;
-	__u32 size;
-	union compat_i2c_smbus_data __user *data;
-};
-
 #define I2C_MINORS	(MINORMASK + 1)
 static LIST_HEAD(i2c_dev_list);
 static DEFINE_SPINLOCK(i2c_dev_list_lock);
@@ -253,17 +235,14 @@ static int i2cdev_check_addr(struct i2c_adapter *adapter, unsigned int addr)
 static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
 		unsigned nmsgs, struct i2c_msg *msgs)
 {
-	u8 __user **data_ptrs = NULL;
-	u16 *orig_lens = NULL;
+	u8 __user **data_ptrs;
 	int i, res;
 
-	res = -ENOMEM;
 	data_ptrs = kmalloc_array(nmsgs, sizeof(u8 __user *), GFP_KERNEL);
-	if (data_ptrs == NULL)
-		goto out;
-	orig_lens = kmalloc_array(nmsgs, sizeof(u16), GFP_KERNEL);
-	if (orig_lens == NULL)
-		goto out;
+	if (data_ptrs == NULL) {
+		kfree(msgs);
+		return -ENOMEM;
+	}
 
 	res = 0;
 	for (i = 0; i < nmsgs; i++) {
@@ -274,30 +253,12 @@ static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
 		}
 
 		data_ptrs[i] = (u8 __user *)msgs[i].buf;
-		msgs[i].buf = NULL;
-		if (msgs[i].len < 1) {
-			/* Sanity check */
-			res = -EINVAL;
-			break;
-
-		}
-		/* Allocate a larger buffer to accommodate possible 255 byte
-		 * blocks. Read results will be dropped later
-		 * if they are too large for the original length.
-		 */
-		orig_lens[i] = msgs[i].len;
-		msgs[i].buf = kmalloc(msgs[i].len + I2C_SMBUS_V3_BLOCK_MAX,
-			GFP_USER | __GFP_NOWARN);
+		msgs[i].buf = memdup_user(data_ptrs[i], msgs[i].len);
 		if (IS_ERR(msgs[i].buf)) {
 			res = PTR_ERR(msgs[i].buf);
 			break;
 		}
-		if (copy_from_user(msgs[i].buf, data_ptrs[i], msgs[i].len)) {
-			kfree(msgs[i].buf);
-			res = -EFAULT;
-			break;
-		}
-		/* Buffer from kmalloc, so DMA is ok */
+		/* memdup_user allocates with GFP_KERNEL, so DMA is ok */
 		msgs[i].flags |= I2C_M_DMA_SAFE;
 
 		/*
@@ -313,7 +274,7 @@ static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
 		 */
 		if (msgs[i].flags & I2C_M_RECV_LEN) {
 			if (!(msgs[i].flags & I2C_M_RD) ||
-			    msgs[i].buf[0] < 1 ||
+			    msgs[i].len < 1 || msgs[i].buf[0] < 1 ||
 			    msgs[i].len < msgs[i].buf[0] +
 					     I2C_SMBUS_BLOCK_MAX) {
 				i++;
@@ -336,16 +297,12 @@ static noinline int i2cdev_ioctl_rdwr(struct i2c_client *client,
 	res = i2c_transfer(client->adapter, msgs, nmsgs);
 	while (i-- > 0) {
 		if (res >= 0 && (msgs[i].flags & I2C_M_RD)) {
-			if (orig_lens[i] < msgs[i].len)
-				res = -EINVAL;
-			else if (copy_to_user(data_ptrs[i], msgs[i].buf,
-						 msgs[i].len))
+			if (copy_to_user(data_ptrs[i], msgs[i].buf,
+					 msgs[i].len))
 				res = -EFAULT;
 		}
 		kfree(msgs[i].buf);
 	}
-out:
-	kfree(orig_lens);
 	kfree(data_ptrs);
 	kfree(msgs);
 	return res;
@@ -353,7 +310,7 @@ out:
 
 static noinline int i2cdev_ioctl_smbus(struct i2c_client *client,
 		u8 read_write, u8 command, u32 size,
-		union compat_i2c_smbus_data __user *data)
+		union i2c_smbus_data __user *data)
 {
 	union i2c_smbus_data temp = {};
 	int datasize, res;
@@ -414,16 +371,6 @@ static noinline int i2cdev_ioctl_smbus(struct i2c_client *client,
 		if (copy_from_user(&temp, data, datasize))
 			return -EFAULT;
 	}
-	if ((size == I2C_SMBUS_BLOCK_PROC_CALL ||
-	    size == I2C_SMBUS_I2C_BLOCK_DATA ||
-	    size == I2C_SMBUS_BLOCK_DATA) &&
-	    read_write == I2C_SMBUS_WRITE &&
-	    temp.block[0] > I2C_SMBUS_BLOCK_MAX) {
-		/* Don't accept writes larger than the buffer size */
-		dev_dbg(&client->adapter->dev, "block write is too large");
-		return -EINVAL;
-
-	}
 	if (size == I2C_SMBUS_I2C_BLOCK_BROKEN) {
 		/* Convert old I2C block commands to the new
 		   convention. This preserves binary compatibility. */
@@ -433,21 +380,9 @@ static noinline int i2cdev_ioctl_smbus(struct i2c_client *client,
 	}
 	res = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
 	      read_write, command, size, &temp);
-	if (res)
-		return res;
-	if ((size == I2C_SMBUS_BLOCK_PROC_CALL ||
-	    size == I2C_SMBUS_I2C_BLOCK_DATA ||
-	    size == I2C_SMBUS_BLOCK_DATA) &&
-	    read_write == I2C_SMBUS_READ &&
-	    temp.block[0] > I2C_SMBUS_BLOCK_MAX) {
-		/* Don't accept reads larger than the buffer size */
-		dev_dbg(&client->adapter->dev, "block read is too large");
-		return -EINVAL;
-
-	}
-	if ((size == I2C_SMBUS_PROC_CALL) ||
-	    (size == I2C_SMBUS_BLOCK_PROC_CALL) ||
-	    (read_write == I2C_SMBUS_READ)) {
+	if (!res && ((size == I2C_SMBUS_PROC_CALL) ||
+		     (size == I2C_SMBUS_BLOCK_PROC_CALL) ||
+		     (read_write == I2C_SMBUS_READ))) {
 		if (copy_to_user(data, &temp, datasize))
 			return -EFAULT;
 	}