3 files changed, 40 insertions, 35 deletions

diff --git a/fs/compat.c b/fs/compat.c
index 52cfeb61da77..ff66c0d7583d 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -606,14 +606,14 @@ ssize_t compat_rw_copy_check_uvector(int type,
         /*
          * 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
+         * ssize_t.
          *
-         * Be careful here because iov_len is a size_t not an ssize_t
+         * In Linux, the total length is limited to MAX_RW_COUNT, there is
+         * no overflow possibility.
          */
         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;
 
@@ -624,13 +624,13 @@ ssize_t compat_rw_copy_check_uvector(int type,
                 }
                 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), compat_ptr(buf), len)) {
                         ret = -EFAULT;
                         goto out;
                 }
+                if (len > MAX_RW_COUNT - tot_len)
+                        len = MAX_RW_COUNT - tot_len;
+                tot_len += len;
                 iov->iov_base = compat_ptr(buf);
                 iov->iov_len = (compat_size_t) len;
                 uvector++;
diff --git a/fs/read_write.c b/fs/read_write.c
index 9cd9d148105d..431a0ed610c8 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -243,8 +243,6 @@ bad:
  * them to something that fits in "int" so that others
  * won't have to do range checks all the time.
  */
-#define MAX_RW_COUNT (INT_MAX & PAGE_CACHE_MASK)
-
 int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count)
 {
         struct inode *inode;
@@ -584,65 +582,71 @@ ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
                               unsigned long nr_segs, unsigned long fast_segs,
                               struct iovec *fast_pointer,
                               struct iovec **ret_pointer)
-  {
+{
         unsigned long seg;
-        ssize_t ret;
+        ssize_t ret;
         struct iovec *iov = fast_pointer;
 
-        /*
-         * 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...
-         */
+        /*
+         * 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) {
                 ret = 0;
-                goto out;
+                goto out;
         }
 
-        /*
-         * First get the "struct iovec" from user memory and
-         * verify all the pointers
-         */
+        /*
+         * First get the "struct iovec" from user memory and
+         * verify all the pointers
+         */
         if (nr_segs > UIO_MAXIOV) {
                 ret = -EINVAL;
-                goto out;
+                goto out;
         }
         if (nr_segs > fast_segs) {
-                iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL);
+                iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL);
                 if (iov == NULL) {
                         ret = -ENOMEM;
-                        goto out;
+                        goto out;
                 }
-        }
+        }
         if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector))) {
                 ret = -EFAULT;
-                goto out;
+                goto out;
         }
 
-        /*
+        /*
          * According to the Single Unix Specification we should return EINVAL
          * if an element length is < 0 when cast to ssize_t or if the
          * total length would overflow the ssize_t return value of the
          * system call.
-         */
+         *
+         * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
+         * overflow case.
+         */
         ret = 0;
-        for (seg = 0; seg < nr_segs; seg++) {
-                void __user *buf = iov[seg].iov_base;
-                ssize_t len = (ssize_t)iov[seg].iov_len;
+        for (seg = 0; seg < nr_segs; seg++) {
+                void __user *buf = iov[seg].iov_base;
+                ssize_t len = (ssize_t)iov[seg].iov_len;
 
                 /* see if we we're about to use an invalid len or if
                  * it's about to overflow ssize_t */
-                if (len < 0 || (ret + len < ret)) {
+                if (len < 0) {
                         ret = -EINVAL;
-                        goto out;
+                        goto out;
                 }
                 if (unlikely(!access_ok(vrfy_dir(type), buf, len))) {
                         ret = -EFAULT;
-                        goto out;
+                        goto out;
+                }
+                if (len > MAX_RW_COUNT - ret) {
+                        len = MAX_RW_COUNT - ret;
+                        iov[seg].iov_len = len;
                 }
-
                 ret += len;
-        }
+        }
 out:
         *ret_pointer = iov;
         return ret;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4d07902bc50c..7b7b507ffa1c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1867,6 +1867,7 @@ extern int current_umask(void);
 /* /sys/fs */
 extern struct kobject *fs_kobj;
 
+#define MAX_RW_COUNT (INT_MAX & PAGE_CACHE_MASK)
 extern int rw_verify_area(int, struct file *, loff_t *, size_t);
 
 #define FLOCK_VERIFY_READ  1