ebiederm@xxxxxxxxxxxx (Eric W. Biederman) writes:
> Cyrill Gorcunov <gorcunov@xxxxxxxxx> writes:
>
>> On Fri, Oct 28, 2016 at 12:39:18AM +0300, Cyrill Gorcunov wrote:
>>> On Thu, Oct 27, 2016 at 10:54:34AM -0500, Eric W. Biederman wrote:
>>> >
>>> >
>>> > I can't imagine either of these changes making a practical difference
>>> > to anyone but I am calling them out in case someone can.
>>> >
>>> > include/linux/mm_types.h | 1 +
>>> > kernel/fork.c | 9 ++++++---
>>> > kernel/ptrace.c | 26 +++++++++++---------------
>>> > mm/init-mm.c | 2 ++
>>> > 4 files changed, 20 insertions(+), 18 deletions(-)
>>>
>>> Thanks a huge, Eric! And really sorry for delay in response,
>>> I managed to miss this quite important mail for me in mail
>>> storm. Gonna test it and will write you the results. Overall looks
>>> great, but better be sure and run the tests.
>>>
>>> Reviewed-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
>>
>> Eric, on which kernel the patch is on top of?
>> It doesn't apply on linux-next for some reason.
>>
>> | Date: Thu Oct 27 14:21:59 2016 +1100
>> |
>> | Add linux-next specific files for 20161027
>> |
>> | Signed-off-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
>>
>> I applied it on Linus' master and tests passed fine
>> (but they were passing fine even without the patch,
>> only linux-next failed).
>
> Odd. I don't think I have taken the old version out of
> linux-next yet. So you can probably revert the old version out of
> linux-next and apply this one. All of my development at this point is
> against v4.9-rc1.
>
> I suspect you will find my last version on top of against v4.9-rc1 will
> pass. Since my tree is only one deep and I don't think anyone except
> linux-next is based on it, I plan to drop and readd this patch.
> Especially since it is candidate for backporting.
Mind if I add your tested-by?
To see Linus's tree fail with my patch you can apply the patch below.
That is the essence of what I changed to fix things. Just ignoring
dumpable when an mm exists.
Eric
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 44a25a1e6e83..b53983ee3f03 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -272,7 +272,7 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
ok:
rcu_read_unlock();
mm = task->mm;
- if (mm &&
+ if (!mm ||
((get_dumpable(mm) != SUID_DUMP_USER) &&
!ptrace_has_cap(mm->user_ns, mode)))
return -EPERM;
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