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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <417a9682-c7fc-fec4-3510-81a8aa7cd0af@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/31/19 5:49 PM, Dmitry Safonov wrote: > Hi Adrian, > > On 7/31/19 5:12 PM, Adrian Reber wrote: > [..] >> @@ -2530,14 +2530,12 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, >> struct clone_args __user *uargs, >> size_t size) >> { >> + struct pid_namespace *pid_ns = task_active_pid_ns(current); >> struct clone_args args; >> >> if (unlikely(size > PAGE_SIZE)) >> return -E2BIG; >> >> - if (unlikely(size < sizeof(struct clone_args))) >> - return -EINVAL; >> - > > It might be better to validate it still somehow, but I don't insist. > > [..] >> @@ -2578,11 +2580,16 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, >> >> static bool clone3_args_valid(const struct kernel_clone_args *kargs) >> { >> - /* >> - * All lower bits of the flag word are taken. >> - * Verify that no other unknown flags are passed along. >> - */ >> - if (kargs->flags & ~CLONE_LEGACY_FLAGS) >> + /* Verify that no other unknown flags are passed along. */ >> + if (kargs->flags & ~(CLONE_LEGACY_FLAGS | CLONE_SET_TID)) >> + return false; >> + >> + /* Fail if set_tid is set without CLONE_SET_TID */ >> + if (kargs->set_tid && !(kargs->flags & CLONE_SET_TID)) >> + return false; >> + >> + /* Also fail if set_tid is invalid */ >> + if ((kargs->set_tid <= 0) && (kargs->flags & CLONE_SET_TID)) >> return false; > > Sorry for not mentioning it on v1, but I've noticed it only now: > you check kargs->set_tid even with the legacy-sized kernel_clone_args, > which is probably some random value on a task's stack? Self-correction: On kernel stack in copy_clone_args_from_user(). Which may probably be considered as a security leak.. Sorry again for not spotting it in v1. Thanks, Dmitry