* [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal @ 2019-09-10 11:57 Eugene Syromiatnikov 2019-09-10 12:20 ` Dmitry V. Levin 2019-09-10 12:44 ` Oleg Nesterov 0 siblings, 2 replies; 10+ messages in thread From: Eugene Syromiatnikov @ 2019-09-10 11:57 UTC (permalink / raw) To: linux-kernel, Christian Brauner Cc: Andrew Morton, Peter Zijlstra (Intel), Ingo Molnar, Dmitry V. Levin, Eric Biederman, Oleg Nesterov Previously, higher 32 bits of exit_signal fields were lost when copied to the kernel args structure (that uses int as a type for the respective field). Fail with EINVAL if these are set as it looks like there's no sane reason to accept them. * kernel/fork.c (copy_clone_args_from_user): Fail with -EINVAL if args.exit_signal converted to unsigned int is not equal to the original value. Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com> --- kernel/fork.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/fork.c b/kernel/fork.c index 2852d0e..fcbc4d5 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2562,6 +2562,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, if (copy_from_user(&args, uargs, size)) return -EFAULT; + if (unlikely(((unsigned int)args.exit_signal) != args.exit_signal)) + return -EINVAL; + *kargs = (struct kernel_clone_args){ .flags = args.flags, .pidfd = u64_to_user_ptr(args.pidfd), -- 2.1.4 ^ permalink raw reply related [flat|nested] 10+ messages in thread
* Re: [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal 2019-09-10 11:57 [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal Eugene Syromiatnikov @ 2019-09-10 12:20 ` Dmitry V. Levin 2019-09-10 12:44 ` Oleg Nesterov 1 sibling, 0 replies; 10+ messages in thread From: Dmitry V. Levin @ 2019-09-10 12:20 UTC (permalink / raw) To: Eugene Syromiatnikov, Christian Brauner Cc: linux-kernel, Andrew Morton, Peter Zijlstra (Intel), Ingo Molnar, Eric Biederman, Oleg Nesterov On Tue, Sep 10, 2019 at 12:57:11PM +0100, Eugene Syromiatnikov wrote: > Previously, higher 32 bits of exit_signal fields were lost when > copied to the kernel args structure (that uses int as a type for the > respective field). Fail with EINVAL if these are set as it looks like > there's no sane reason to accept them. > > * kernel/fork.c (copy_clone_args_from_user): Fail with -EINVAL if > args.exit_signal converted to unsigned int is not equal to the original > value. > > Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com> Reviewed-by: Dmitry V. Levin <ldv@altlinux.org> -- ldv ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal 2019-09-10 11:57 [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal Eugene Syromiatnikov 2019-09-10 12:20 ` Dmitry V. Levin @ 2019-09-10 12:44 ` Oleg Nesterov 2019-09-10 13:09 ` Christian Brauner 1 sibling, 1 reply; 10+ messages in thread From: Oleg Nesterov @ 2019-09-10 12:44 UTC (permalink / raw) To: Eugene Syromiatnikov Cc: linux-kernel, Christian Brauner, Andrew Morton, Peter Zijlstra (Intel), Ingo Molnar, Dmitry V. Levin, Eric Biederman On 09/10, Eugene Syromiatnikov wrote: > > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -2562,6 +2562,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, > if (copy_from_user(&args, uargs, size)) > return -EFAULT; > > + if (unlikely(((unsigned int)args.exit_signal) != args.exit_signal)) > + return -EINVAL; Hmm. Unless I am totally confused you found a serious bug... Without CLONE_THREAD/CLONE_PARENT copy_process() blindly does p->exit_signal = args->exit_signal; the valid_signal(sig) check in do_notify_parent() mostly saves us, but we must not allow child->exit_signal < 0, if nothing else this breaks thread_group_leader(). And afaics this patch doesn't fix this? I think we need the valid_signal() check... Oleg. ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal 2019-09-10 12:44 ` Oleg Nesterov @ 2019-09-10 13:09 ` Christian Brauner 2019-09-10 13:10 ` Christian Brauner 0 siblings, 1 reply; 10+ messages in thread From: Christian Brauner @ 2019-09-10 13:09 UTC (permalink / raw) To: Oleg Nesterov Cc: Eugene Syromiatnikov, linux-kernel, Christian Brauner, Andrew Morton, Peter Zijlstra (Intel), Ingo Molnar, Dmitry V. Levin, Eric Biederman On Tue, Sep 10, 2019 at 02:44:41PM +0200, Oleg Nesterov wrote: > On 09/10, Eugene Syromiatnikov wrote: > > > > --- a/kernel/fork.c > > +++ b/kernel/fork.c > > @@ -2562,6 +2562,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, > > if (copy_from_user(&args, uargs, size)) > > return -EFAULT; > > > > + if (unlikely(((unsigned int)args.exit_signal) != args.exit_signal)) > > + return -EINVAL; > > Hmm. Unless I am totally confused you found a serious bug... > > Without CLONE_THREAD/CLONE_PARENT copy_process() blindly does > > p->exit_signal = args->exit_signal; > > the valid_signal(sig) check in do_notify_parent() mostly saves us, but we > must not allow child->exit_signal < 0, if nothing else this breaks > thread_group_leader(). > > And afaics this patch doesn't fix this? I think we need the valid_signal() > check... Thanks for sending this patch so quickly after our conversation yesterday, Eugene! We definitely want valid_signal() to verify the signal is ok. Eugene, can you please update the patch to use valid signal and keep it as a separate patch from the cleanup and selftest patches? Christian ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal 2019-09-10 13:09 ` Christian Brauner @ 2019-09-10 13:10 ` Christian Brauner 2019-09-10 13:27 ` Christian Brauner 0 siblings, 1 reply; 10+ messages in thread From: Christian Brauner @ 2019-09-10 13:10 UTC (permalink / raw) To: Oleg Nesterov Cc: Eugene Syromiatnikov, linux-kernel, Christian Brauner, Andrew Morton, Peter Zijlstra (Intel), Ingo Molnar, Dmitry V. Levin, Eric Biederman On Tue, Sep 10, 2019 at 03:09:35PM +0200, Christian Brauner wrote: > On Tue, Sep 10, 2019 at 02:44:41PM +0200, Oleg Nesterov wrote: > > On 09/10, Eugene Syromiatnikov wrote: > > > > > > --- a/kernel/fork.c > > > +++ b/kernel/fork.c > > > @@ -2562,6 +2562,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, > > > if (copy_from_user(&args, uargs, size)) > > > return -EFAULT; > > > > > > + if (unlikely(((unsigned int)args.exit_signal) != args.exit_signal)) > > > + return -EINVAL; > > > > Hmm. Unless I am totally confused you found a serious bug... > > > > Without CLONE_THREAD/CLONE_PARENT copy_process() blindly does > > > > p->exit_signal = args->exit_signal; > > > > the valid_signal(sig) check in do_notify_parent() mostly saves us, but we > > must not allow child->exit_signal < 0, if nothing else this breaks > > thread_group_leader(). > > > > And afaics this patch doesn't fix this? I think we need the valid_signal() > > check... > > Thanks for sending this patch so quickly after our conversation > yesterday, Eugene! > We definitely want valid_signal() to verify the signal is ok. > > Eugene, can you please update the patch to use valid signal and keep it > as a separate patch from the cleanup and selftest patches? I'll then pick this up quickly so we can get this in before 5.3 is out. Thanks! Christian ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal 2019-09-10 13:10 ` Christian Brauner @ 2019-09-10 13:27 ` Christian Brauner 2019-09-10 14:27 ` Eugene Syromiatnikov 2019-09-10 14:39 ` Oleg Nesterov 0 siblings, 2 replies; 10+ messages in thread From: Christian Brauner @ 2019-09-10 13:27 UTC (permalink / raw) To: Oleg Nesterov Cc: Eugene Syromiatnikov, linux-kernel, Christian Brauner, Andrew Morton, Peter Zijlstra (Intel), Ingo Molnar, Dmitry V. Levin, Eric Biederman On Tue, Sep 10, 2019 at 03:10:48PM +0200, Christian Brauner wrote: > On Tue, Sep 10, 2019 at 03:09:35PM +0200, Christian Brauner wrote: > > On Tue, Sep 10, 2019 at 02:44:41PM +0200, Oleg Nesterov wrote: > > > On 09/10, Eugene Syromiatnikov wrote: > > > > > > > > --- a/kernel/fork.c > > > > +++ b/kernel/fork.c > > > > @@ -2562,6 +2562,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, > > > > if (copy_from_user(&args, uargs, size)) > > > > return -EFAULT; > > > > > > > > + if (unlikely(((unsigned int)args.exit_signal) != args.exit_signal)) > > > > + return -EINVAL; > > > > > > Hmm. Unless I am totally confused you found a serious bug... > > > > > > Without CLONE_THREAD/CLONE_PARENT copy_process() blindly does > > > > > > p->exit_signal = args->exit_signal; > > > > > > the valid_signal(sig) check in do_notify_parent() mostly saves us, but we > > > must not allow child->exit_signal < 0, if nothing else this breaks > > > thread_group_leader(). > > > > > > And afaics this patch doesn't fix this? I think we need the valid_signal() > > > check... > > > > Thanks for sending this patch so quickly after our conversation > > yesterday, Eugene! > > We definitely want valid_signal() to verify the signal is ok. So we could do your check in copy_clone_args_from_user(), and then we do another valid_signal() check in clone3_args_valid()? We could do the latter in copy_clone_args_from_user() too but it's nicer to do it along the other checks in clone3_args_valid(). Christian ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal 2019-09-10 13:27 ` Christian Brauner @ 2019-09-10 14:27 ` Eugene Syromiatnikov 2019-09-10 14:39 ` Oleg Nesterov 1 sibling, 0 replies; 10+ messages in thread From: Eugene Syromiatnikov @ 2019-09-10 14:27 UTC (permalink / raw) To: Christian Brauner Cc: Oleg Nesterov, linux-kernel, Christian Brauner, Andrew Morton, Peter Zijlstra (Intel), Ingo Molnar, Dmitry V. Levin, Eric Biederman On Tue, Sep 10, 2019 at 03:27:02PM +0200, Christian Brauner wrote: > On Tue, Sep 10, 2019 at 03:10:48PM +0200, Christian Brauner wrote: > > On Tue, Sep 10, 2019 at 03:09:35PM +0200, Christian Brauner wrote: > > > On Tue, Sep 10, 2019 at 02:44:41PM +0200, Oleg Nesterov wrote: > > > > On 09/10, Eugene Syromiatnikov wrote: > > > > > > > > > > --- a/kernel/fork.c > > > > > +++ b/kernel/fork.c > > > > > @@ -2562,6 +2562,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, > > > > > if (copy_from_user(&args, uargs, size)) > > > > > return -EFAULT; > > > > > > > > > > + if (unlikely(((unsigned int)args.exit_signal) != args.exit_signal)) > > > > > + return -EINVAL; > > > > > > > > Hmm. Unless I am totally confused you found a serious bug... > > > > > > > > Without CLONE_THREAD/CLONE_PARENT copy_process() blindly does > > > > > > > > p->exit_signal = args->exit_signal; > > > > > > > > the valid_signal(sig) check in do_notify_parent() mostly saves us, but we > > > > must not allow child->exit_signal < 0, if nothing else this breaks > > > > thread_group_leader(). > > > > > > > > And afaics this patch doesn't fix this? I think we need the valid_signal() > > > > check... > > > > > > Thanks for sending this patch so quickly after our conversation > > > yesterday, Eugene! > > > We definitely want valid_signal() to verify the signal is ok. > > So we could do your check in copy_clone_args_from_user(), and then we do > another valid_signal() check in clone3_args_valid()? We could do the > latter in copy_clone_args_from_user() too but it's nicer to do it along > the other checks in clone3_args_valid(). There's also a discrepancy between CSIGNAL (0xff) and _NSIG, used in valid_signal (which is between 32 and 128, depending on architecture), it seems it doesn't break thread_group_leader, but definitely allows passing some invalid signal numbers via legacy clone-like syscalls—I'm not sure if that's important. > Christian ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal 2019-09-10 13:27 ` Christian Brauner 2019-09-10 14:27 ` Eugene Syromiatnikov @ 2019-09-10 14:39 ` Oleg Nesterov 2019-09-10 14:46 ` Christian Brauner 1 sibling, 1 reply; 10+ messages in thread From: Oleg Nesterov @ 2019-09-10 14:39 UTC (permalink / raw) To: Christian Brauner Cc: Eugene Syromiatnikov, linux-kernel, Christian Brauner, Andrew Morton, Peter Zijlstra (Intel), Ingo Molnar, Dmitry V. Levin, Eric Biederman On 09/10, Christian Brauner wrote: > On Tue, Sep 10, 2019 at 03:10:48PM +0200, Christian Brauner wrote: > > On Tue, Sep 10, 2019 at 03:09:35PM +0200, Christian Brauner wrote: > > > On Tue, Sep 10, 2019 at 02:44:41PM +0200, Oleg Nesterov wrote: > > > > On 09/10, Eugene Syromiatnikov wrote: > > > > > > > > > > --- a/kernel/fork.c > > > > > +++ b/kernel/fork.c > > > > > @@ -2562,6 +2562,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, > > > > > if (copy_from_user(&args, uargs, size)) > > > > > return -EFAULT; > > > > > > > > > > + if (unlikely(((unsigned int)args.exit_signal) != args.exit_signal)) > > > > > + return -EINVAL; > > > > > > > > Hmm. Unless I am totally confused you found a serious bug... > > > > > > > > Without CLONE_THREAD/CLONE_PARENT copy_process() blindly does > > > > > > > > p->exit_signal = args->exit_signal; > > > > > > > > the valid_signal(sig) check in do_notify_parent() mostly saves us, but we > > > > must not allow child->exit_signal < 0, if nothing else this breaks > > > > thread_group_leader(). > > > > > > > > And afaics this patch doesn't fix this? I think we need the valid_signal() > > > > check... > > > > > > Thanks for sending this patch so quickly after our conversation > > > yesterday, Eugene! > > > We definitely want valid_signal() to verify the signal is ok. > > So we could do your check in copy_clone_args_from_user(), and then we do > another valid_signal() check in clone3_args_valid()? We could do the > latter in copy_clone_args_from_user() too but it's nicer to do it along > the other checks in clone3_args_valid(). I am fine either way. Sure, we can add valid_signal() into clone3_args_valid(), but then I'd ask to simplify the "overflow" check above. Something like if (args.exit_signal > UINT_MAX) return -EINVAL; looks much more readable to me. Or we can simply do if (args.exit_signal & ~((u64)CSIGNAL)) return -EINVAL; in copy_clone_args_from_user() and forget about all problems. Up to Eugene and you. Oleg. ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal 2019-09-10 14:39 ` Oleg Nesterov @ 2019-09-10 14:46 ` Christian Brauner 2019-09-10 15:18 ` Eugene Syromiatnikov 0 siblings, 1 reply; 10+ messages in thread From: Christian Brauner @ 2019-09-10 14:46 UTC (permalink / raw) To: Oleg Nesterov Cc: Eugene Syromiatnikov, linux-kernel, Christian Brauner, Andrew Morton, Peter Zijlstra (Intel), Ingo Molnar, Dmitry V. Levin, Eric Biederman On Tue, Sep 10, 2019 at 04:39:44PM +0200, Oleg Nesterov wrote: > On 09/10, Christian Brauner wrote: > > On Tue, Sep 10, 2019 at 03:10:48PM +0200, Christian Brauner wrote: > > > On Tue, Sep 10, 2019 at 03:09:35PM +0200, Christian Brauner wrote: > > > > On Tue, Sep 10, 2019 at 02:44:41PM +0200, Oleg Nesterov wrote: > > > > > On 09/10, Eugene Syromiatnikov wrote: > > > > > > > > > > > > --- a/kernel/fork.c > > > > > > +++ b/kernel/fork.c > > > > > > @@ -2562,6 +2562,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, > > > > > > if (copy_from_user(&args, uargs, size)) > > > > > > return -EFAULT; > > > > > > > > > > > > + if (unlikely(((unsigned int)args.exit_signal) != args.exit_signal)) > > > > > > + return -EINVAL; > > > > > > > > > > Hmm. Unless I am totally confused you found a serious bug... > > > > > > > > > > Without CLONE_THREAD/CLONE_PARENT copy_process() blindly does > > > > > > > > > > p->exit_signal = args->exit_signal; > > > > > > > > > > the valid_signal(sig) check in do_notify_parent() mostly saves us, but we > > > > > must not allow child->exit_signal < 0, if nothing else this breaks > > > > > thread_group_leader(). > > > > > > > > > > And afaics this patch doesn't fix this? I think we need the valid_signal() > > > > > check... > > > > > > > > Thanks for sending this patch so quickly after our conversation > > > > yesterday, Eugene! > > > > We definitely want valid_signal() to verify the signal is ok. > > > > So we could do your check in copy_clone_args_from_user(), and then we do > > another valid_signal() check in clone3_args_valid()? We could do the > > latter in copy_clone_args_from_user() too but it's nicer to do it along > > the other checks in clone3_args_valid(). > > I am fine either way. Sure, we can add valid_signal() into clone3_args_valid(), > but then I'd ask to simplify the "overflow" check above. Something like > > if (args.exit_signal > UINT_MAX) > return -EINVAL; > > looks much more readable to me. > > > Or we can simply do > > if (args.exit_signal & ~((u64)CSIGNAL)) > return -EINVAL; > > in copy_clone_args_from_user() and forget about all problems. Both are fine with me. The latter might have the advantage that we catch both legacy clone and clone3. I think Eugene prefers this as well. Christian ^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal 2019-09-10 14:46 ` Christian Brauner @ 2019-09-10 15:18 ` Eugene Syromiatnikov 0 siblings, 0 replies; 10+ messages in thread From: Eugene Syromiatnikov @ 2019-09-10 15:18 UTC (permalink / raw) To: Christian Brauner Cc: Oleg Nesterov, linux-kernel, Christian Brauner, Andrew Morton, Peter Zijlstra (Intel), Ingo Molnar, Dmitry V. Levin, Eric Biederman On Tue, Sep 10, 2019 at 04:46:15PM +0200, Christian Brauner wrote: > On Tue, Sep 10, 2019 at 04:39:44PM +0200, Oleg Nesterov wrote: > > On 09/10, Christian Brauner wrote: > > > On Tue, Sep 10, 2019 at 03:10:48PM +0200, Christian Brauner wrote: > > > > On Tue, Sep 10, 2019 at 03:09:35PM +0200, Christian Brauner wrote: > > > > > On Tue, Sep 10, 2019 at 02:44:41PM +0200, Oleg Nesterov wrote: > > > > > > On 09/10, Eugene Syromiatnikov wrote: > > > > > > > > > > > > > > --- a/kernel/fork.c > > > > > > > +++ b/kernel/fork.c > > > > > > > @@ -2562,6 +2562,9 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs, > > > > > > > if (copy_from_user(&args, uargs, size)) > > > > > > > return -EFAULT; > > > > > > > > > > > > > > + if (unlikely(((unsigned int)args.exit_signal) != args.exit_signal)) > > > > > > > + return -EINVAL; > > > > > > > > > > > > Hmm. Unless I am totally confused you found a serious bug... > > > > > > > > > > > > Without CLONE_THREAD/CLONE_PARENT copy_process() blindly does > > > > > > > > > > > > p->exit_signal = args->exit_signal; > > > > > > > > > > > > the valid_signal(sig) check in do_notify_parent() mostly saves us, but we > > > > > > must not allow child->exit_signal < 0, if nothing else this breaks > > > > > > thread_group_leader(). > > > > > > > > > > > > And afaics this patch doesn't fix this? I think we need the valid_signal() > > > > > > check... > > > > > > > > > > Thanks for sending this patch so quickly after our conversation > > > > > yesterday, Eugene! > > > > > We definitely want valid_signal() to verify the signal is ok. > > > > > > So we could do your check in copy_clone_args_from_user(), and then we do > > > another valid_signal() check in clone3_args_valid()? We could do the > > > latter in copy_clone_args_from_user() too but it's nicer to do it along > > > the other checks in clone3_args_valid(). > > > > I am fine either way. Sure, we can add valid_signal() into clone3_args_valid(), > > but then I'd ask to simplify the "overflow" check above. Something like > > > > if (args.exit_signal > UINT_MAX) > > return -EINVAL; > > > > looks much more readable to me. > > > > > > Or we can simply do > > > > if (args.exit_signal & ~((u64)CSIGNAL)) > > return -EINVAL; > > > > in copy_clone_args_from_user() and forget about all problems. > > Both are fine with me. The latter might have the advantage that we catch > both legacy clone and clone3. I think Eugene prefers this as well. Unfortunately, it doesn't. I think, the best place for the check is either in _do_fork or copy_process itself; however, it's quite messy as that way it's detached from the other checks, but, at the same time, there are a lot of code paths (like the one in arch/x86/ia32/sys_ia32.c), and it's kinda obscure that the caller of _do_fork has to check that exit_syscall is positive itself. > Christian ^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2019-09-10 15:18 UTC | newest] Thread overview: 10+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2019-09-10 11:57 [PATCH] fork: fail on non-zero higher 32 bits of args.exit_signal Eugene Syromiatnikov 2019-09-10 12:20 ` Dmitry V. Levin 2019-09-10 12:44 ` Oleg Nesterov 2019-09-10 13:09 ` Christian Brauner 2019-09-10 13:10 ` Christian Brauner 2019-09-10 13:27 ` Christian Brauner 2019-09-10 14:27 ` Eugene Syromiatnikov 2019-09-10 14:39 ` Oleg Nesterov 2019-09-10 14:46 ` Christian Brauner 2019-09-10 15:18 ` Eugene Syromiatnikov
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