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81895a65ec
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. This was
done mechanically with this coccinelle script:
@basic@
expression E;
type T;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
typedef u64;
@@
(
- ((T)get_random_u32() % (E))
+ prandom_u32_max(E)
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- ((T)get_random_u32() & ((E) - 1))
+ prandom_u32_max(E * XXX_MAKE_SURE_E_IS_POW2)
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- ((u64)(E) * get_random_u32() >> 32)
+ prandom_u32_max(E)
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- ((T)get_random_u32() & ~PAGE_MASK)
+ prandom_u32_max(PAGE_SIZE)
)
@multi_line@
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
identifier RAND;
expression E;
@@
- RAND = get_random_u32();
... when != RAND
- RAND %= (E);
+ RAND = prandom_u32_max(E);
// Find a potential literal
@literal_mask@
expression LITERAL;
type T;
identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32";
position p;
@@
((T)get_random_u32()@p & (LITERAL))
// Add one to the literal.
@script:python add_one@
literal << literal_mask.LITERAL;
RESULT;
@@
value = None
if literal.startswith('0x'):
value = int(literal, 16)
elif literal[0] in '123456789':
value = int(literal, 10)
if value is None:
print("I don't know how to handle %s" % (literal))
cocci.include_match(False)
elif value == 2**32 - 1 or value == 2**31 - 1 or value == 2**24 - 1 or value == 2**16 - 1 or value == 2**8 - 1:
print("Skipping 0x%x for cleanup elsewhere" % (value))
cocci.include_match(False)
elif value & (value + 1) != 0:
print("Skipping 0x%x because it's not a power of two minus one" % (value))
cocci.include_match(False)
elif literal.startswith('0x'):
coccinelle.RESULT = cocci.make_expr("0x%x" % (value + 1))
else:
coccinelle.RESULT = cocci.make_expr("%d" % (value + 1))
// Replace the literal mask with the calculated result.
@plus_one@
expression literal_mask.LITERAL;
position literal_mask.p;
expression add_one.RESULT;
identifier FUNC;
@@
- (FUNC()@p & (LITERAL))
+ prandom_u32_max(RESULT)
@collapse_ret@
type T;
identifier VAR;
expression E;
@@
{
- T VAR;
- VAR = (E);
- return VAR;
+ return E;
}
@drop_var@
type T;
identifier VAR;
@@
{
- T VAR;
... when != VAR
}
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: KP Singh <kpsingh@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz> # for ext4 and sbitmap
Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> # for drbd
Acked-by: Jakub Kicinski <kuba@kernel.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com> # for s390
Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # for mmc
Acked-by: Darrick J. Wong <djwong@kernel.org> # for xfs
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
106 lines
3.1 KiB
C
106 lines
3.1 KiB
C
/*
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* Copyright (c) 2011 Chelsio Communications. All rights reserved.
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*
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* This software is available to you under a choice of one of two
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* licenses. You may choose to be licensed under the terms of the GNU
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* General Public License (GPL) Version 2, available from the file
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* COPYING in the main directory of this source tree, or the
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* OpenIB.org BSD license below:
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* - Redistributions of source code must retain the above
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* copyright notice, this list of conditions and the following
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* disclaimer.
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*
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* - Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials
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* provided with the distribution.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include <linux/kernel.h>
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#include <linux/random.h>
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#include "iw_cxgb4.h"
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#define RANDOM_SKIP 16
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/*
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* Trivial bitmap-based allocator. If the random flag is set, the
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* allocator is designed to:
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* - pseudo-randomize the id returned such that it is not trivially predictable.
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* - avoid reuse of recently used id (at the expense of predictability)
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*/
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u32 c4iw_id_alloc(struct c4iw_id_table *alloc)
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{
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unsigned long flags;
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u32 obj;
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spin_lock_irqsave(&alloc->lock, flags);
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obj = find_next_zero_bit(alloc->table, alloc->max, alloc->last);
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if (obj >= alloc->max)
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obj = find_first_zero_bit(alloc->table, alloc->max);
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if (obj < alloc->max) {
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if (alloc->flags & C4IW_ID_TABLE_F_RANDOM)
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alloc->last += prandom_u32_max(RANDOM_SKIP);
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else
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alloc->last = obj + 1;
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if (alloc->last >= alloc->max)
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alloc->last = 0;
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__set_bit(obj, alloc->table);
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obj += alloc->start;
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} else
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obj = -1;
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spin_unlock_irqrestore(&alloc->lock, flags);
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return obj;
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}
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void c4iw_id_free(struct c4iw_id_table *alloc, u32 obj)
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{
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unsigned long flags;
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obj -= alloc->start;
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spin_lock_irqsave(&alloc->lock, flags);
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__clear_bit(obj, alloc->table);
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spin_unlock_irqrestore(&alloc->lock, flags);
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}
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int c4iw_id_table_alloc(struct c4iw_id_table *alloc, u32 start, u32 num,
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u32 reserved, u32 flags)
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{
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alloc->start = start;
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alloc->flags = flags;
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if (flags & C4IW_ID_TABLE_F_RANDOM)
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alloc->last = prandom_u32_max(RANDOM_SKIP);
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else
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alloc->last = 0;
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alloc->max = num;
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spin_lock_init(&alloc->lock);
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alloc->table = bitmap_zalloc(num, GFP_KERNEL);
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if (!alloc->table)
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return -ENOMEM;
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if (!(alloc->flags & C4IW_ID_TABLE_F_EMPTY))
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bitmap_set(alloc->table, 0, reserved);
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return 0;
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}
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void c4iw_id_table_free(struct c4iw_id_table *alloc)
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{
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bitmap_free(alloc->table);
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}
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