From: David Laight <David.Laight@ACULAB.COM>
To: "'Jason A. Donenfeld'" <Jason@zx2c4.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"patches@lists.linux.dev" <patches@lists.linux.dev>
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Subject: RE: [PATCH v4 2/6] treewide: use prandom_u32_max() when possible
Date: Sat, 8 Oct 2022 22:08:03 +0000 [thread overview]
Message-ID: <01fafe0e56554b1c9c934c458b93473a@AcuMS.aculab.com> (raw)
In-Reply-To: <20221007180107.216067-3-Jason@zx2c4.com>
From: Jason A. Donenfeld
> Sent: 07 October 2022 19:01
>
> Rather than incurring a division or requesting too many random bytes for
> the given range, use the prandom_u32_max() function, which only takes
> the minimum required bytes from the RNG and avoids divisions.
>
...
> --- a/lib/cmdline_kunit.c
> +++ b/lib/cmdline_kunit.c
> @@ -76,7 +76,7 @@ static void cmdline_test_lead_int(struct kunit *test)
> int rc = cmdline_test_values[i];
> int offset;
>
> - sprintf(in, "%u%s", prandom_u32_max(256), str);
> + sprintf(in, "%u%s", get_random_int() % 256, str);
> /* Only first '-' after the number will advance the pointer */
> offset = strlen(in) - strlen(str) + !!(rc == 2);
> cmdline_do_one_test(test, in, rc, offset);
> @@ -94,7 +94,7 @@ static void cmdline_test_tail_int(struct kunit *test)
> int rc = strcmp(str, "") ? (strcmp(str, "-") ? 0 : 1) : 1;
> int offset;
>
> - sprintf(in, "%s%u", str, prandom_u32_max(256));
> + sprintf(in, "%s%u", str, get_random_int() % 256);
> /*
> * Only first and leading '-' not followed by integer
> * will advance the pointer.
Something has gone backwards here....
And get_random_u8() looks a better fit.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-10-08 22:09 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-07 18:01 [PATCH v4 0/6] treewide cleanup of random integer usage Jason A. Donenfeld
2022-10-07 18:01 ` [PATCH v4 1/6] treewide: use prandom_u32_max() when possible, mechanically Jason A. Donenfeld
2022-10-07 21:14 ` Darrick J. Wong
2022-10-07 18:01 ` [PATCH v4 2/6] treewide: use prandom_u32_max() when possible Jason A. Donenfeld
2022-10-07 21:17 ` Darrick J. Wong
2022-10-08 1:28 ` Jason A. Donenfeld
2022-10-07 22:47 ` Kees Cook
2022-10-08 2:21 ` Jason A. Donenfeld
2022-10-08 3:21 ` Jason A. Donenfeld
2022-10-08 22:08 ` David Laight [this message]
2022-10-08 22:19 ` Jason A. Donenfeld
2022-10-07 18:01 ` [PATCH v4 3/6] treewide: use get_random_{u8,u16}() " Jason A. Donenfeld
2022-10-07 18:01 ` [PATCH v4 4/6] treewide: use get_random_u32() " Jason A. Donenfeld
2022-10-07 20:34 ` Rolf Eike Beer
2022-10-08 1:40 ` Jason A. Donenfeld
2022-10-07 21:19 ` Darrick J. Wong
2022-10-08 22:18 ` David Laight
2022-10-08 22:37 ` Jason A. Donenfeld
2022-10-09 0:26 ` Jason A. Donenfeld
2022-10-07 18:01 ` [PATCH v4 5/6] treewide: use get_random_bytes " Jason A. Donenfeld
2022-10-07 18:01 ` [PATCH v4 6/6] prandom: remove unused functions Jason A. Donenfeld
2022-10-08 3:50 [PATCH v4 2/6] treewide: use prandom_u32_max() when possible Kees Cook
2022-10-08 7:33 ` Julia Lawall
2022-10-08 18:16 ` Andy Shevchenko
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