Re: [LTP] [PATCH] syscalls/semctl03: Solve kernel panic in semctl03

[Richard Palethorpe <rpalethorpe@suse.de>]

Hello,

Dylan Jhong <dylan@andestech.com> writes:

> Hi Richard,
>
> Thanks for your reply.
> My opinion is the same as yours, libc should do more checking and
> protection for incoming parameters

This is not my opinion.

Are you saying that libc segfaults? This is an acceptable outcome for
the LTP. To stop the test failing we can fork the test and check if the
child segfaults. However it seems the EFAULT test is already skipped if
we use libc, which is also acceptable.

However the patch title says that this resulted in a kernel panic due to
a null pointer dereference? This is a serious kernel bug that may be
exploitable.

>
> In semctl03.c, the two tv->semctl() implementation functions, which are libc_semctl() and sys_semctl(),
> do not pass the 4th argument ".buf" to the next level system call.
> At present, the 4th argument of semctl() implemented in semctl03.c is hard-coded,
> I think passing parameters instead of hardcoding should be more better for this testcase.
> Should we pass all parameters to the next level semctl() system call?

A 4th arg is never passed, if you remove the vararg the test compiles
and runs fine. So the vararg should be removed, but this is relatively
minor compared to a kernel null pointer dereference.

-- 
Thank you,
Richard.

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