From: Javier Martinez Canillas javierm@redhat.com
[ Upstream commit 94dc3471d1b2b58b3728558d0e3f264e9ce6ff59 ]
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.
Signed-off-by: Javier Martinez Canillas javierm@redhat.com Tested-by: Peter Robinson pbrobinson@gmail.com Reviewed-by: Thomas Zimmermann tzimmermann@suse.de Link: https://patchwork.freedesktop.org/patch/msgid/20220705100215.572498-2-javier... Signed-off-by: Sasha Levin sashal@kernel.org --- 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 ce26e8fea9c2..335fad8b209a 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -437,7 +437,7 @@ 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);