* Re: [PATCH] kernel/exit.c: pointer sighand could be uninitialized [not found] <CABvMjLTfuDqNEt4+1E6R47UFQOj7N1SAhb3KCwxjHsxm7itaog@mail.gmail.com> @ 2018-05-03 4:50 ` Kees Cook 2018-05-03 5:06 ` Al Viro 1 sibling, 0 replies; 3+ messages in thread From: Kees Cook @ 2018-05-03 4:50 UTC (permalink / raw) To: Yizhuo Zhai Cc: Al Viro, Ingo Molnar, Andrew Morton, Paul E. McKenney, LKML, Chengyu Song, Zhiyun Qian On Wed, May 2, 2018 at 6:48 PM, Yizhuo Zhai <yzhai003@ucr.edu> wrote: > Variable 'sighand' could be uninitialized if probe_kernel_address fails > (-EFAULT). The later use in the if statement may lead to undefined behavior. > > Signed-off-by: yzhai003@ucr.edu <yzhai003@ucr.edu> > --- > kernel/exit.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/exit.c b/kernel/exit.c > index f6cad39..a353bd1 100644 > --- a/kernel/exit.c > +++ b/kernel/exit.c > @@ -232,7 +232,7 @@ void release_task(struct task_struct *p) > */ > struct task_struct *task_rcu_dereference(struct task_struct **ptask) > { > - struct sighand_struct *sighand; > + struct sighand_struct *sighand = NULL; > struct task_struct *task; > > /* Better would probably be to check the return of probe_kernel_address() and take appropriate action... -Kees -- Kees Cook Pixel Security ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] kernel/exit.c: pointer sighand could be uninitialized [not found] <CABvMjLTfuDqNEt4+1E6R47UFQOj7N1SAhb3KCwxjHsxm7itaog@mail.gmail.com> 2018-05-03 4:50 ` [PATCH] kernel/exit.c: pointer sighand could be uninitialized Kees Cook @ 2018-05-03 5:06 ` Al Viro 2018-05-03 6:44 ` Chengyu Song 1 sibling, 1 reply; 3+ messages in thread From: Al Viro @ 2018-05-03 5:06 UTC (permalink / raw) To: Yizhuo Zhai Cc: mingo, keescook, akpm, paulmck, linux-kernel, Chengyu Song, Zhiyun Qian On Wed, May 02, 2018 at 06:48:57PM -0700, Yizhuo Zhai wrote: > Variable 'sighand' could be uninitialized if probe_kernel_address fails > (-EFAULT). The later use in the if statement may lead to undefined behavior. Excuse me, but that's nonsense. The value *copied* into it (in case probe_kernel_address() has not failed) may be just as uninitialized. If mere "compare uninitialized pointer value to NULL" can cause nasal demons to fly, * we are screwed anyway * the piece of crap compiler should be printed on sandpaper and used to polish its authors. Read the comments in there, please. Especially the one regarding the second case. ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] kernel/exit.c: pointer sighand could be uninitialized 2018-05-03 5:06 ` Al Viro @ 2018-05-03 6:44 ` Chengyu Song 0 siblings, 0 replies; 3+ messages in thread From: Chengyu Song @ 2018-05-03 6:44 UTC (permalink / raw) To: Al Viro Cc: Yizhuo Zhai, mingo, keescook, akpm, paulmck, linux-kernel, Zhiyun Qian Right. Should have checked the commit history ... this has been brought up before: > Peter Zijlstra - May 18, 2016, 5:02 p.m. > > > +struct task_struct *task_rcu_dereference(struct task_struct **ptask) > > +{ > > + struct task_struct *task; > > + struct sighand_struct *sighand; > > I think that needs: ' = NULL', and led to the comments added there. Sorry for wasting your time. -chengyu > On May 2, 2018, at 10:06 PM, Al Viro <viro@zeniv.linux.org.uk> wrote: > > On Wed, May 02, 2018 at 06:48:57PM -0700, Yizhuo Zhai wrote: >> Variable 'sighand' could be uninitialized if probe_kernel_address fails >> (-EFAULT). The later use in the if statement may lead to undefined behavior. > > Excuse me, but that's nonsense. The value *copied* into it (in case > probe_kernel_address() has not failed) may be just as uninitialized. > If mere "compare uninitialized pointer value to NULL" can cause nasal demons to fly, > * we are screwed anyway > * the piece of crap compiler should be printed on sandpaper and used to > polish its authors. > > Read the comments in there, please. Especially the one regarding the second case. ^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-05-03 4:50 ` [PATCH] kernel/exit.c: pointer sighand could be uninitialized Kees Cook
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2018-05-03 6:44 ` Chengyu Song
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