From: Javier Martinez Canillas javierm@redhat.com
stable inclusion from stable-v5.10.150 commit e7d701800365d2dd3ef2252497dcaed9a2d2fada category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I6D0XA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
--------------------------------
[ 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 Signed-off-by: Jialin Zhang zhangjialin11@huawei.com --- 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 4606cc938b36..a15d55d06510 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -473,7 +473,7 @@ 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);