vhost: fix to check the return value of copy_to/from_user() correctly

copy_to/from_user() returns the number of bytes that could not be copied.

So we need to check if it is not zero, and in that case, we should return
the error number -EFAULT rather than directly return the return value from
copy_to/from_user().

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 44f123a..e366202 100644 (file)
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -320,10 +320,8 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
 {
        struct vhost_memory mem, *newmem, *oldmem;
        unsigned long size = offsetof(struct vhost_memory, regions);
-       long r;
-       r = copy_from_user(&mem, m, size);
-       if (r)
-               return r;
+       if (copy_from_user(&mem, m, size))
+               return -EFAULT;
        if (mem.padding)
                return -EOPNOTSUPP;
        if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
@@ -333,11 +331,10 @@ static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
                return -ENOMEM;
 
        memcpy(newmem, &mem, size);
-       r = copy_from_user(newmem->regions, m->regions,
-                          mem.nregions * sizeof *m->regions);
-       if (r) {
+       if (copy_from_user(newmem->regions, m->regions,
+                          mem.nregions * sizeof *m->regions)) {
                kfree(newmem);
-               return r;
+               return -EFAULT;
        }
 
        if (!memory_access_ok(d, newmem, vhost_has_feature(d, VHOST_F_LOG_ALL)))
@@ -389,9 +386,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
                        r = -EBUSY;
                        break;
                }
-               r = copy_from_user(&s, argp, sizeof s);
-               if (r < 0)
+               if (copy_from_user(&s, argp, sizeof s)) {
+                       r = -EFAULT;
                        break;
+               }
                if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
                        r = -EINVAL;
                        break;
@@ -405,9 +403,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
                        r = -EBUSY;
                        break;
                }
-               r = copy_from_user(&s, argp, sizeof s);
-               if (r < 0)
+               if (copy_from_user(&s, argp, sizeof s)) {
+                       r = -EFAULT;
                        break;
+               }
                if (s.num > 0xffff) {
                        r = -EINVAL;
                        break;
@@ -419,12 +418,14 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
        case VHOST_GET_VRING_BASE:
                s.index = idx;
                s.num = vq->last_avail_idx;
-               r = copy_to_user(argp, &s, sizeof s);
+               if (copy_to_user(argp, &s, sizeof s))
+                       r = -EFAULT;
                break;
        case VHOST_SET_VRING_ADDR:
-               r = copy_from_user(&a, argp, sizeof a);
-               if (r < 0)
+               if (copy_from_user(&a, argp, sizeof a)) {
+                       r = -EFAULT;
                        break;
+               }
                if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
                        r = -EOPNOTSUPP;
                        break;
@@ -477,9 +478,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
                vq->used = (void __user *)(unsigned long)a.used_user_addr;
                break;
        case VHOST_SET_VRING_KICK:
-               r = copy_from_user(&f, argp, sizeof f);
-               if (r < 0)
+               if (copy_from_user(&f, argp, sizeof f)) {
+                       r = -EFAULT;
                        break;
+               }
                eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
                if (IS_ERR(eventfp)) {
                        r = PTR_ERR(eventfp);
@@ -492,9 +494,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
                        filep = eventfp;
                break;
        case VHOST_SET_VRING_CALL:
-               r = copy_from_user(&f, argp, sizeof f);
-               if (r < 0)
+               if (copy_from_user(&f, argp, sizeof f)) {
+                       r = -EFAULT;
                        break;
+               }
                eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
                if (IS_ERR(eventfp)) {
                        r = PTR_ERR(eventfp);
@@ -510,9 +513,10 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
                        filep = eventfp;
                break;
        case VHOST_SET_VRING_ERR:
-               r = copy_from_user(&f, argp, sizeof f);
-               if (r < 0)
+               if (copy_from_user(&f, argp, sizeof f)) {
+                       r = -EFAULT;
                        break;
+               }
                eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
                if (IS_ERR(eventfp)) {
                        r = PTR_ERR(eventfp);
@@ -575,9 +579,10 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
                r = vhost_set_memory(d, argp);
                break;
        case VHOST_SET_LOG_BASE:
-               r = copy_from_user(&p, argp, sizeof p);
-               if (r < 0)
+               if (copy_from_user(&p, argp, sizeof p)) {
+                       r = -EFAULT;
                        break;
+               }
                if ((u64)(unsigned long)p != p) {
                        r = -EFAULT;
                        break;