linux/net/xfrm
Jason A. Donenfeld 81895a65ec treewide: use prandom_u32_max() when possible, part 1
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)
|
- ((T)get_random_u32() & ((E) - 1))
+ prandom_u32_max(E * XXX_MAKE_SURE_E_IS_POW2)
|
- ((u64)(E) * get_random_u32() >> 32)
+ prandom_u32_max(E)
|
- ((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>
2022-10-11 17:42:55 -06:00
..
espintcp.c net-next: skbuff: refactor pskb_pull 2022-09-30 12:31:46 +01:00
Kconfig xfrm/compat: Add 32=>64-bit messages translator 2020-09-24 08:53:03 +02:00
Makefile xfrm: Provide API to register translator module 2020-09-24 08:53:03 +02:00
xfrm_algo.c xfrm: Add support for SM4 symmetric cipher algorithm 2021-12-23 09:32:51 +01:00
xfrm_compat.c xfrm: rate limit SA mapping change message to user space 2021-12-23 09:32:51 +01:00
xfrm_device.c xfrm: add extack support to xfrm_dev_state_add 2022-09-22 07:36:07 +02:00
xfrm_hash.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
xfrm_hash.h xfrm: add state hashtable keyed by seq 2021-05-14 13:52:01 +02:00
xfrm_inout.h xfrm: move xfrm4_extract_header to common helper 2020-05-06 09:40:08 +02:00
xfrm_input.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-10-03 17:44:18 -07:00
xfrm_interface.c xfrm: lwtunnel: add lwtunnel support for xfrm interfaces in collect_md mode 2022-08-29 10:44:08 +02:00
xfrm_ipcomp.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-10-03 17:44:18 -07:00
xfrm_output.c Revert "xfrm: update SA curlft.use_time" 2022-08-03 07:27:37 +02:00
xfrm_policy.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next 2022-10-03 07:52:13 +01:00
xfrm_proc.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
xfrm_replay.c xfrm: add extack support to xfrm_init_replay 2022-09-22 07:36:08 +02:00
xfrm_state.c treewide: use prandom_u32_max() when possible, part 1 2022-10-11 17:42:55 -06:00
xfrm_sysctl.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xfrm_user.c xfrm: add extack support to xfrm_init_replay 2022-09-22 07:36:08 +02:00