| Message ID | 20220701120755.2135100-2-javierm@redhat.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
| Series | drm: A couple of fixes for drm_copy_field() helper function | expand |
Am 01.07.22 um 14:07 schrieb Javier Martinez Canillas: > The strlen() function returns a size_t which is an unsigned int on 32-bit > arches and an unsigned long on 64-bit arches. But in the drm_copy_field() > function, the strlen() return value is assigned to an 'int len' variable. > > Later, the len variable is passed as copy_from_user() third argument that > is an unsigned long parameter as well. > > In theory, this can lead to an integer overflow via type conversion. Since > the assignment happens to a signed int lvalue instead of a size_t lvalue. > > In practice though, that's unlikely since the values copied are set by DRM > drivers and not controlled by userspace. But using a size_t for len is the > correct thing to do anyways. > > Reported-by: Peter Robinson <pbrobinson@gmail.com> > Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> > --- > > drivers/gpu/drm/drm_ioctl.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c > index 8faad23dc1d8..e1b9a03e619c 100644 > --- a/drivers/gpu/drm/drm_ioctl.c > +++ b/drivers/gpu/drm/drm_ioctl.c > @@ -472,7 +472,7 @@ EXPORT_SYMBOL(drm_invalid_op); > */ > static int drm_copy_field(char __user *buf, size_t *buf_len, const char *value) > { > - int len; > + size_t len; > > /* don't overflow userbuf */ > len = strlen(value);
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index 8faad23dc1d8..e1b9a03e619c 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -472,7 +472,7 @@ EXPORT_SYMBOL(drm_invalid_op); */ static int drm_copy_field(char __user *buf, size_t *buf_len, const char *value) { - int len; + size_t len; /* don't overflow userbuf */ len = strlen(value);
The strlen() function returns a size_t which is an unsigned int on 32-bit arches and an unsigned long on 64-bit arches. But in the drm_copy_field() function, the strlen() return value is assigned to an 'int len' variable. Later, the len variable is passed as copy_from_user() third argument that is an unsigned long parameter as well. In theory, this can lead to an integer overflow via type conversion. Since the assignment happens to a signed int lvalue instead of a size_t lvalue. In practice though, that's unlikely since the values copied are set by DRM drivers and not controlled by userspace. But using a size_t for len is the correct thing to do anyways. Reported-by: Peter Robinson <pbrobinson@gmail.com> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> --- drivers/gpu/drm/drm_ioctl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)