Date: Tue, 3 Nov 2020 10:55:25 +0100 From: Hans Petter Selasky <hps@selasky.org> To: xtouqh@hotmail.com, hackers@freebsd.org Subject: Re: KASSERT(val != 0) not triggering in linux_errno.c reading outside of array Message-ID: <77d2eef0-9cc8-aa39-6d28-a7fb41e233ac@selasky.org> In-Reply-To: <AM0PR06MB39867F0AE62A737D2EE596F5C0110@AM0PR06MB3986.eurprd06.prod.outlook.com> References: <AM0PR06MB39867F0AE62A737D2EE596F5C0110@AM0PR06MB3986.eurprd06.prod.outlook.com>
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On 2020-11-03 10:46, xtouqh@hotmail.com wrote: > I'm looking at the current sys/compat/linux/linux_errno.c source, > specifically this function: > https://svnweb.freebsd.org/base/head/sys/compat/linux/linux_errno.c?revision=367132&view=markup#l24, > and noticed that sizeof() usage there seems to be bogus as I mentioned > in https://reviews.freebsd.org/D26974#inline-168811. > > What I'm wondering about is why KASSERT() is not triggering there -- I > have added the following printf() right below KASSERT() showing that we > indeed read outside of the array, and some of the linux_errtbl[i] values > are 0: > > printf("%s:linux_errtbl[%d]=%d\n", __func__, i, linux_errtbl[i]); > > But, if I add the following check before printf(), it seems to be never > true: > > if (linux_errtbl[i] == 0) > printf("%s:linux_errtbl[%d]=%d\n", __func__, i, linux_errtbl[i]); > > So how come printed values are 0, but KASSERT(value != 0) and if (value > == 0) are never true? I tried to reproduce this in simple userland test > case, but the check seems to be working correctly there (though still > reading outside of array if using sizeof() for final index). What am I > missing here? Did you enable INVARIANTS when compiling the kernel? --HPS
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