From: David Laight <David.Laight@ACULAB.COM>
To: 'Linus Torvalds' <torvalds@linux-foundation.org>
Cc: Kees Cook <keescook@chromium.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
Christoph Hellwig <hch@infradead.org>,
"Jason A. Donenfeld" <Jason@zx2c4.com>
Subject: RE: [PATCH next v3 0/5] minmax: Relax type checks in min() and max().
Date: Thu, 24 Aug 2023 09:05:28 +0000 [thread overview]
Message-ID: <bcf2fcad28c048058c808ec9e749da80@AcuMS.aculab.com> (raw)
In-Reply-To: <CAHk-=wh1SFzTM1nWwC30t55jzZradQmJ4942CDD1pM_umhU_Vw@mail.gmail.com>
From: Linus Torvalds
> Sent: Wednesday, August 23, 2023 4:32 PM
...
> That might get rid of a number of the more annoying cases.
The one it leaves is code like:
int length = get_length(...);
if (length <= 0)
return error:
do {
frag_len = some_min_function(length, PAGE_SIZE);
...
} while ((length -= frag_len) != 0);
As written it is ok for all reasonable some_min_function().
But if the (length <= 0) test is missing it really doesn't
matter what some_min_function() returns because the code
isn't going to do anything sensible - and may just loop.
About the only thing you could do is add a run-time check
and then BUG() if negative.
But that is horrid...
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
prev parent reply other threads:[~2023-08-24 9:06 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-04 10:50 [PATCH next v3 0/5] minmax: Relax type checks in min() and max() David Laight
2023-08-04 10:53 ` [PATCH v3 1/5] minmax: Add min_unsigned(a, b) and max_unsigned(a, b) David Laight
2023-08-04 10:54 ` [PATCH v3 2/5] minmax: Allow min()/max()/clamp() if the arguments have the same signedness David Laight
2023-08-04 10:55 ` [PATCH v3 3/5] minmax: Fix indentation of __cmp_once() and __clamp_once() David Laight
2023-08-04 10:55 ` [PATCH v3 4/5] minmax: Allow comparisons of 'int' against 'unsigned char/short' David Laight
2023-08-04 10:56 ` [PATCH v3 5/5] minmax: Relax check to allow comparison between int and small unsigned constants David Laight
2023-08-04 18:14 ` Linus Torvalds
2023-08-07 10:50 ` David Laight
2023-08-07 15:48 ` Linus Torvalds
2023-08-10 8:29 ` David Laight
2023-08-10 19:46 ` Linus Torvalds
2023-08-14 8:04 ` David Laight
2023-08-14 14:51 ` David Laight
2023-08-14 15:29 ` David Laight
2023-08-14 21:21 ` [PATCH next v3 0/5] minmax: Relax type checks in min() and max() Kees Cook
2023-08-15 8:55 ` David Laight
2023-08-21 18:24 ` Kees Cook
2023-08-22 17:35 ` Linus Torvalds
2023-08-23 8:42 ` David Laight
2023-08-23 8:52 ` David Laight
2023-08-23 15:32 ` Linus Torvalds
2023-08-24 9:05 ` David Laight [this message]
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