2 files changed, 53 insertions, 31 deletions

diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
index 6fb495ea956a..86ad50a900c8 100644
--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -235,11 +235,11 @@ static inline __must_check unsigned int kfifo_out_locked(struct kfifo *fifo,
 
 extern void kfifo_skip(struct kfifo *fifo, unsigned int len);
 
-extern __must_check unsigned int kfifo_from_user(struct kfifo *fifo,
-        const void __user *from, unsigned int n);
+extern __must_check int kfifo_from_user(struct kfifo *fifo,
+        const void __user *from, unsigned int n, unsigned *lenout);
 
-extern __must_check unsigned int kfifo_to_user(struct kfifo *fifo,
-        void __user *to, unsigned int n);
+extern __must_check int kfifo_to_user(struct kfifo *fifo,
+        void __user *to, unsigned int n, unsigned *lenout);
 
 /*
  * __kfifo_add_out internal helper function for updating the out offset
diff --git a/kernel/kfifo.c b/kernel/kfifo.c
index ab615e695052..b50bb622e8b0 100644
--- a/kernel/kfifo.c
+++ b/kernel/kfifo.c
@@ -159,8 +159,9 @@ static inline void __kfifo_out_data(struct kfifo *fifo,
         memcpy(to + l, fifo->buffer, len - l);
 }
 
-static inline unsigned int __kfifo_from_user_data(struct kfifo *fifo,
-         const void __user *from, unsigned int len, unsigned int off)
+static inline int __kfifo_from_user_data(struct kfifo *fifo,
+         const void __user *from, unsigned int len, unsigned int off,
+         unsigned *lenout)
 {
         unsigned int l;
         int ret;
@@ -177,16 +178,20 @@ static inline unsigned int __kfifo_from_user_data(struct kfifo *fifo,
         /* first put the data starting from fifo->in to buffer end */
         l = min(len, fifo->size - off);
         ret = copy_from_user(fifo->buffer + off, from, l);
-
-        if (unlikely(ret))
-                return ret + len - l;
+        if (unlikely(ret)) {
+                *lenout = ret;
+                return -EFAULT;
+        }
+        *lenout = l;
 
         /* then put the rest (if any) at the beginning of the buffer */
-        return copy_from_user(fifo->buffer, from + l, len - l);
+        ret = copy_from_user(fifo->buffer, from + l, len - l);
+        *lenout += ret ? ret : len - l;
+        return ret ? -EFAULT : 0;
 }
 
-static inline unsigned int __kfifo_to_user_data(struct kfifo *fifo,
-                void __user *to, unsigned int len, unsigned int off)
+static inline int __kfifo_to_user_data(struct kfifo *fifo,
+                void __user *to, unsigned int len, unsigned int off, unsigned *lenout)
 {
         unsigned int l;
         int ret;
@@ -203,12 +208,21 @@ static inline unsigned int __kfifo_to_user_data(struct kfifo *fifo,
         /* first get the data from fifo->out until the end of the buffer */
         l = min(len, fifo->size - off);
         ret = copy_to_user(to, fifo->buffer + off, l);
-
-        if (unlikely(ret))
-                return ret + len - l;
+        *lenout = l;
+        if (unlikely(ret)) {
+                *lenout -= ret;
+                return -EFAULT;
+        }
 
         /* then get the rest (if any) from the beginning of the buffer */
-        return copy_to_user(to + l, fifo->buffer, len - l);
+        len -= l;
+        ret = copy_to_user(to + l, fifo->buffer, len);
+        if (unlikely(ret)) {
+                *lenout += len - ret;
+                return -EFAULT;
+        }
+        *lenout += len;
+        return 0;
 }
 
 unsigned int __kfifo_in_n(struct kfifo *fifo,
@@ -299,10 +313,13 @@ EXPORT_SYMBOL(__kfifo_out_generic);
 unsigned int __kfifo_from_user_n(struct kfifo *fifo,
         const void __user *from, unsigned int len, unsigned int recsize)
 {
+        unsigned total;
+
         if (kfifo_avail(fifo) < len + recsize)
                 return len + 1;
 
-        return __kfifo_from_user_data(fifo, from, len, recsize);
+        __kfifo_from_user_data(fifo, from, len, recsize, &total);
+        return total;
 }
 EXPORT_SYMBOL(__kfifo_from_user_n);
 
@@ -313,18 +330,21 @@ EXPORT_SYMBOL(__kfifo_from_user_n);
  * @len: the length of the data to be added.
  *
  * This function copies at most @len bytes from the @from into the
- * FIFO depending and returns the number of copied bytes.
+ * FIFO depending and returns -EFAULT/0.
  *
  * Note that with only one concurrent reader and one concurrent
  * writer, you don't need extra locking to use these functions.
  */
-unsigned int kfifo_from_user(struct kfifo *fifo,
-        const void __user *from, unsigned int len)
+int kfifo_from_user(struct kfifo *fifo,
+        const void __user *from, unsigned int len, unsigned *total)
 {
+        int ret;
         len = min(kfifo_avail(fifo), len);
-        len -= __kfifo_from_user_data(fifo, from, len, 0);
+        ret = __kfifo_from_user_data(fifo, from, len, 0, total);
+        if (ret)
+                return ret;
         __kfifo_add_in(fifo, len);
-        return len;
+        return 0;
 }
 EXPORT_SYMBOL(kfifo_from_user);
 
@@ -339,17 +359,17 @@ unsigned int __kfifo_to_user_n(struct kfifo *fifo,
         void __user *to, unsigned int len, unsigned int reclen,
         unsigned int recsize)
 {
-        unsigned int ret;
+        unsigned int ret, total;
 
         if (kfifo_len(fifo) < reclen + recsize)
                 return len;
 
-        ret = __kfifo_to_user_data(fifo, to, reclen, recsize);
+        ret = __kfifo_to_user_data(fifo, to, reclen, recsize, &total);
 
         if (likely(ret == 0))
                 __kfifo_add_out(fifo, reclen + recsize);
 
-        return ret;
+        return total;
 }
 EXPORT_SYMBOL(__kfifo_to_user_n);
 
@@ -358,20 +378,22 @@ EXPORT_SYMBOL(__kfifo_to_user_n);
  * @fifo: the fifo to be used.
  * @to: where the data must be copied.
  * @len: the size of the destination buffer.
+ @ @lenout: pointer to output variable with copied data
  *
  * This function copies at most @len bytes from the FIFO into the
- * @to buffer and returns the number of copied bytes.
+ * @to buffer and 0 or -EFAULT.
  *
  * Note that with only one concurrent reader and one concurrent
  * writer, you don't need extra locking to use these functions.
  */
-unsigned int kfifo_to_user(struct kfifo *fifo,
-        void __user *to, unsigned int len)
+int kfifo_to_user(struct kfifo *fifo,
+        void __user *to, unsigned int len, unsigned *lenout)
 {
+        int ret;
         len = min(kfifo_len(fifo), len);
-        len -= __kfifo_to_user_data(fifo, to, len, 0);
-        __kfifo_add_out(fifo, len);
-        return len;
+        ret = __kfifo_to_user_data(fifo, to, len, 0, lenout);
+        __kfifo_add_out(fifo, *lenout);
+        return ret;
 }
 EXPORT_SYMBOL(kfifo_to_user);