2 files changed, 81 insertions, 53 deletions

diff --git a/fs/compat.c b/fs/compat.c
index 05448730f840..7b4aabb3bb36 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -568,6 +568,79 @@ out:
         return ret;
 }
 
+/* A write operation does a read from user space and vice versa */
+#define vrfy_dir(type) ((type) == READ ? VERIFY_WRITE : VERIFY_READ)
+
+ssize_t compat_rw_copy_check_uvector(int type,
+                const struct compat_iovec __user *uvector, unsigned long nr_segs,
+                unsigned long fast_segs, struct iovec *fast_pointer,
+                struct iovec **ret_pointer)
+{
+        compat_ssize_t tot_len;
+        struct iovec *iov = *ret_pointer = fast_pointer;
+        ssize_t ret = 0;
+        int seg;
+
+        /*
+         * SuS says "The readv() function *may* fail if the iovcnt argument
+         * was less than or equal to 0, or greater than {IOV_MAX}.  Linux has
+         * traditionally returned zero for zero segments, so...
+         */
+        if (nr_segs == 0)
+                goto out;
+
+        ret = -EINVAL;
+        if (nr_segs > UIO_MAXIOV || nr_segs < 0)
+                goto out;
+        if (nr_segs > fast_segs) {
+                ret = -ENOMEM;
+                iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL);
+                if (iov == NULL) {
+                        *ret_pointer = fast_pointer;
+                        goto out;
+                }
+        }
+        *ret_pointer = iov;
+
+        /*
+         * Single unix specification:
+         * We should -EINVAL if an element length is not >= 0 and fitting an
+         * ssize_t.  The total length is fitting an ssize_t
+         *
+         * Be careful here because iov_len is a size_t not an ssize_t
+         */
+        tot_len = 0;
+        ret = -EINVAL;
+        for (seg = 0; seg < nr_segs; seg++) {
+                compat_ssize_t tmp = tot_len;
+                compat_uptr_t buf;
+                compat_ssize_t len;
+
+                if (__get_user(len, &uvector->iov_len) ||
+                   __get_user(buf, &uvector->iov_base)) {
+                        ret = -EFAULT;
+                        goto out;
+                }
+                if (len < 0)    /* size_t not fitting in compat_ssize_t .. */
+                        goto out;
+                tot_len += len;
+                if (tot_len < tmp) /* maths overflow on the compat_ssize_t */
+                        goto out;
+                if (!access_ok(vrfy_dir(type), buf, len)) {
+                        ret = -EFAULT;
+                        goto out;
+                }
+                iov->iov_base = compat_ptr(buf);
+                iov->iov_len = (compat_size_t) len;
+                uvector++;
+                iov++;
+        }
+        ret = tot_len;
+
+out:
+        return ret;
+}
+
 static inline long
 copy_iocb(long nr, u32 __user *ptr32, struct iocb __user * __user *ptr64)
 {
@@ -1077,70 +1150,21 @@ static ssize_t compat_do_readv_writev(int type, struct file *file,
 {
         compat_ssize_t tot_len;
         struct iovec iovstack[UIO_FASTIOV];
-        struct iovec *iov=iovstack, *vector;
+        struct iovec *iov;
         ssize_t ret;
-        int seg;
         io_fn_t fn;
         iov_fn_t fnv;
 
-        /*
-         * SuS says "The readv() function *may* fail if the iovcnt argument
-         * was less than or equal to 0, or greater than {IOV_MAX}.  Linux has
-         * traditionally returned zero for zero segments, so...
-         */
-        ret = 0;
-        if (nr_segs == 0)
-                goto out;
-
-        /*
-         * First get the "struct iovec" from user memory and
-         * verify all the pointers
-         */
         ret = -EINVAL;
-        if ((nr_segs > UIO_MAXIOV) || (nr_segs <= 0))
-                goto out;
         if (!file->f_op)
                 goto out;
-        if (nr_segs > UIO_FASTIOV) {
-                ret = -ENOMEM;
-                iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL);
-                if (!iov)
-                        goto out;
-        }
+
         ret = -EFAULT;
         if (!access_ok(VERIFY_READ, uvector, nr_segs*sizeof(*uvector)))
                 goto out;
 
-        /*
-         * Single unix specification:
-         * We should -EINVAL if an element length is not >= 0 and fitting an
-         * ssize_t.  The total length is fitting an ssize_t
-         *
-         * Be careful here because iov_len is a size_t not an ssize_t
-         */
-        tot_len = 0;
-        vector = iov;
-        ret = -EINVAL;
-        for (seg = 0 ; seg < nr_segs; seg++) {
-                compat_ssize_t tmp = tot_len;
-                compat_ssize_t len;
-                compat_uptr_t buf;
-
-                if (__get_user(len, &uvector->iov_len) ||
-                    __get_user(buf, &uvector->iov_base)) {
-                        ret = -EFAULT;
-                        goto out;
-                }
-                if (len < 0)    /* size_t not fitting an compat_ssize_t .. */
-                        goto out;
-                tot_len += len;
-                if (tot_len < tmp) /* maths overflow on the compat_ssize_t */
-                        goto out;
-                vector->iov_base = compat_ptr(buf);
-                vector->iov_len = (compat_size_t) len;
-                uvector++;
-                vector++;
-        }
+        tot_len = compat_rw_copy_check_uvector(type, uvector, nr_segs,
+                                               UIO_FASTIOV, iovstack, &iov);
         if (tot_len == 0) {
                 ret = 0;
                 goto out;
diff --git a/include/linux/compat.h b/include/linux/compat.h
index 717c691ecd8e..168f7daa7bde 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -356,5 +356,9 @@ asmlinkage long compat_sys_newfstatat(unsigned int dfd, char __user * filename,
 asmlinkage long compat_sys_openat(unsigned int dfd, const char __user *filename,
                                   int flags, int mode);
 
+extern ssize_t compat_rw_copy_check_uvector(int type,
+                const struct compat_iovec __user *uvector, unsigned long nr_segs,
+                unsigned long fast_segs, struct iovec *fast_pointer,
+                struct iovec **ret_pointer);
 #endif /* CONFIG_COMPAT */
 #endif /* _LINUX_COMPAT_H */