fix signedness mess in rw_verify_area() on 64bit architectures

... and clean the unsigned-f_pos code, while we are at it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/read_write.c b/fs/read_write.c
index 5d431bacbea967e7a66755bf9320f20d9f464902..5520f8ad550446d095c6483e67acc0ca5522ff91 100644 (file)
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -30,18 +30,9 @@ const struct file_operations generic_ro_fops = {
 
 EXPORT_SYMBOL(generic_ro_fops);
 
-static int
-__negative_fpos_check(struct file *file, loff_t pos, size_t count)
+static inline int unsigned_offsets(struct file *file)
 {
-       /*
-        * pos or pos+count is negative here, check overflow.
-        * too big "count" will be caught in rw_verify_area().
-        */
-       if ((pos < 0) && (pos + count < pos))
-               return -EOVERFLOW;
-       if (file->f_mode & FMODE_UNSIGNED_OFFSET)
-               return 0;
-       return -EINVAL;
+       return file->f_mode & FMODE_UNSIGNED_OFFSET;
 }
 
 /**
@@ -75,7 +66,7 @@ generic_file_llseek_unlocked(struct file *file, loff_t offset, int origin)
                break;
        }
 
-       if (offset < 0 && __negative_fpos_check(file, offset, 0))
+       if (offset < 0 && !unsigned_offsets(file))
                return -EINVAL;
        if (offset > inode->i_sb->s_maxbytes)
                return -EINVAL;
@@ -152,7 +143,7 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
                        offset += file->f_pos;
        }
        retval = -EINVAL;
-       if (offset >= 0 || !__negative_fpos_check(file, offset, 0)) {
+       if (offset >= 0 || unsigned_offsets(file)) {
                if (offset != file->f_pos) {
                        file->f_pos = offset;
                        file->f_version = 0;
@@ -252,9 +243,13 @@ int rw_verify_area(int read_write, struct file *file, loff_t *ppos, size_t count
        if (unlikely((ssize_t) count < 0))
                return retval;
        pos = *ppos;
-       if (unlikely((pos < 0) || (loff_t) (pos + count) < 0)) {
-               retval = __negative_fpos_check(file, pos, count);
-               if (retval)
+       if (unlikely(pos < 0)) {
+               if (!unsigned_offsets(file))
+                       return retval;
+               if (count >= -pos) /* both values are in 0..LLONG_MAX */
+                       return -EOVERFLOW;
+       } else if (unlikely((loff_t) (pos + count) < 0)) {
+               if (!unsigned_offsets(file))
                        return retval;
        }