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From: Vineet Gupta <Vineet.Gupta1@synopsys.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: linux-arch <linux-arch@vger.kernel.org>,
	Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>,
	Khalid Aziz <khalid.aziz@oracle.com>,
	Peter Zijlstra <peterz@infradead.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Aleksa Sarai <cyphar@cyphar.com>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	"linux-snps-arc@lists.infradead.org"
	<linux-snps-arc@lists.infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>
Subject: Re: [RFC 2/4] lib/strncpy_from_user: Remove redundant user space pointer range check
Date: Wed, 15 Jan 2020 23:00:17 +0000
Message-ID: <ff24ea2b-e232-36a2-4e11-c89400feff45@synopsys.com> (raw)
In-Reply-To: <CAAeHK+zxVw6jOu-NzjR14U_i5cpDynE=OC3D5WswTvqT8o5NhQ@mail.gmail.com>

On 1/15/20 6:42 AM, Andrey Konovalov wrote:
>> -       max_addr = user_addr_max();
>> -       src_addr = (unsigned long)untagged_addr(src);
>
> If you end up changing this code, you need to keep the untagged_addr()
> logic, otherwise this breaks arm64 tagged address ABI [1].

It is moot point now, but fwiw untagged_addr() would not have been needed anymore
as it was only needed to compute the pointer difference which my patch got rid of.

> 
> [1] https://www.kernel.org/doc/html/latest/arm64/tagged-address-abi.html
> 
>> -       if (likely(src_addr < max_addr)) {
>> -               unsigned long max = max_addr - src_addr;
>> +       kasan_check_write(dst, count);
>> +       check_object_size(dst, count, false);
>> +       if (user_access_begin(src, count)) {

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Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14 20:08 [RFC 0/4] Switching ARC to optimized generic strncpy_from_user Vineet Gupta
2020-01-14 20:08 ` [RFC 1/4] asm-generic/uaccess: don't define inline functions if noinline lib/* in use Vineet Gupta
2020-01-14 20:57   ` Arnd Bergmann
2020-01-15 23:01     ` Vineet Gupta
2020-01-16 11:43       ` Arnd Bergmann
2020-01-14 21:32   ` Linus Torvalds
2020-01-15  9:08     ` Arnd Bergmann
2020-01-15 14:12       ` Al Viro
2020-01-15 14:21         ` Arnd Bergmann
2020-01-14 20:08 ` [RFC 2/4] lib/strncpy_from_user: Remove redundant user space pointer range check Vineet Gupta
2020-01-14 21:22   ` Linus Torvalds
2020-01-14 21:52     ` Vineet Gupta
2020-01-14 23:46     ` Al Viro
2020-01-15 14:42   ` Andrey Konovalov
2020-01-15 23:00     ` Vineet Gupta [this message]
2020-01-14 20:08 ` [RFC 3/4] ARC: uaccess: remove noinline variants of __strncpy_from_user() and friends Vineet Gupta
2020-01-14 20:08 ` [RFC 4/4] ARC: uaccess: use optimized generic __strnlen_user/__strncpy_from_user Vineet Gupta
2020-01-14 20:42   ` Arnd Bergmann
2020-01-14 21:36     ` Vineet Gupta
2020-01-14 21:49       ` Linus Torvalds
2020-01-14 22:14         ` Vineet Gupta

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