This is a note to let you know that I've just added the patch titled drm: Use size_t type for len variable in drm_copy_field() to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-use-size_t-type-for-len-variable-in-drm_copy_fie.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit a3435dc9e39d1f0c7bd80acd5f3e3eae8d98c03b Author: Javier Martinez Canillas <javierm@xxxxxxxxxx> Date: Tue Jul 5 12:02:13 2022 +0200 drm: Use size_t type for len variable in drm_copy_field() [ 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@xxxxxxxxxx> Tested-by: Peter Robinson <pbrobinson@xxxxxxxxx> Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20220705100215.572498-2-javierm@xxxxxxxxxx Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index be4a52dc4d6f..5669c6cf7135 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);