kernel: descrip: Fix copyin/copyout + rw operation

Use ssize_t to avoid unsigned integer underflows and only call copyout()
during file reads

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 9 insertions, 9 deletions

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index 201db3e..d122e89 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -148,6 +148,7 @@ static int
 fd_rw(unsigned int fd, void *buf, size_t count, uint8_t write)
 {
     char *kbuf = NULL;
+    ssize_t n;
     struct filedesc *filedes;
     struct sio_txn sio;
     scret_t retval = 0;
@@ -194,22 +195,21 @@ fd_rw(unsigned int fd, void *buf, size_t count, uint8_t write)
         }
 
         /* Call VFS write hook */
-        if ((count = vfs_vop_write(filedes->vp, &sio)) < 0) {
-            retval = -EIO;
+        if ((n = vfs_vop_write(filedes->vp, &sio)) < 0) {
+            retval = n;
             goto done;
         }
     } else {
-        if ((count = vfs_vop_read(filedes->vp, &sio)) < 0) {
-            retval = -EIO;
+        if ((n = vfs_vop_read(filedes->vp, &sio)) < 0) {
+            retval = n;
             goto done;
         }
-    }
 
-    if (copyout(kbuf, buf, count) < 0) {
-        retval = -EFAULT;
-        goto done;
+        if (copyout(kbuf, buf, count) < 0) {
+            retval = -EFAULT;
+            goto done;
+        }
     }
-
     retval = count;
 done:
     if (kbuf != NULL) {