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authorJason A. Donenfeld <Jason@zx2c4.com>2022-10-05 16:43:38 +0200
committerJason A. Donenfeld <Jason@zx2c4.com>2022-10-11 17:42:55 -0600
commit81895a65ec63ee1daec3255dc1a06675d2fbe915 (patch)
tree03703a64413a07bd4e6a171a449a8f18c760e21c /net/ipv6
parentd465bff130bf4ca17b6980abe51164ace1e0cba4 (diff)
downloadlinux-81895a65ec63ee1daec3255dc1a06675d2fbe915.tar.bz2
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>
Diffstat (limited to 'net/ipv6')
-rw-r--r--net/ipv6/addrconf.c8
-rw-r--r--net/ipv6/mcast.c10
2 files changed, 9 insertions, 9 deletions
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 10ce86bf228e..417834b7169d 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -104,7 +104,7 @@ static inline u32 cstamp_delta(unsigned long cstamp)
static inline s32 rfc3315_s14_backoff_init(s32 irt)
{
/* multiply 'initial retransmission time' by 0.9 .. 1.1 */
- u64 tmp = (900000 + prandom_u32() % 200001) * (u64)irt;
+ u64 tmp = (900000 + prandom_u32_max(200001)) * (u64)irt;
do_div(tmp, 1000000);
return (s32)tmp;
}
@@ -112,11 +112,11 @@ static inline s32 rfc3315_s14_backoff_init(s32 irt)
static inline s32 rfc3315_s14_backoff_update(s32 rt, s32 mrt)
{
/* multiply 'retransmission timeout' by 1.9 .. 2.1 */
- u64 tmp = (1900000 + prandom_u32() % 200001) * (u64)rt;
+ u64 tmp = (1900000 + prandom_u32_max(200001)) * (u64)rt;
do_div(tmp, 1000000);
if ((s32)tmp > mrt) {
/* multiply 'maximum retransmission time' by 0.9 .. 1.1 */
- tmp = (900000 + prandom_u32() % 200001) * (u64)mrt;
+ tmp = (900000 + prandom_u32_max(200001)) * (u64)mrt;
do_div(tmp, 1000000);
}
return (s32)tmp;
@@ -3967,7 +3967,7 @@ static void addrconf_dad_kick(struct inet6_ifaddr *ifp)
if (ifp->flags & IFA_F_OPTIMISTIC)
rand_num = 0;
else
- rand_num = prandom_u32() % (idev->cnf.rtr_solicit_delay ? : 1);
+ rand_num = prandom_u32_max(idev->cnf.rtr_solicit_delay ?: 1);
nonce = 0;
if (idev->cnf.enhanced_dad ||
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index 0566ab03ddbe..7860383295d8 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -1050,7 +1050,7 @@ bool ipv6_chk_mcast_addr(struct net_device *dev, const struct in6_addr *group,
/* called with mc_lock */
static void mld_gq_start_work(struct inet6_dev *idev)
{
- unsigned long tv = prandom_u32() % idev->mc_maxdelay;
+ unsigned long tv = prandom_u32_max(idev->mc_maxdelay);
idev->mc_gq_running = 1;
if (!mod_delayed_work(mld_wq, &idev->mc_gq_work, tv + 2))
@@ -1068,7 +1068,7 @@ static void mld_gq_stop_work(struct inet6_dev *idev)
/* called with mc_lock */
static void mld_ifc_start_work(struct inet6_dev *idev, unsigned long delay)
{
- unsigned long tv = prandom_u32() % delay;
+ unsigned long tv = prandom_u32_max(delay);
if (!mod_delayed_work(mld_wq, &idev->mc_ifc_work, tv + 2))
in6_dev_hold(idev);
@@ -1085,7 +1085,7 @@ static void mld_ifc_stop_work(struct inet6_dev *idev)
/* called with mc_lock */
static void mld_dad_start_work(struct inet6_dev *idev, unsigned long delay)
{
- unsigned long tv = prandom_u32() % delay;
+ unsigned long tv = prandom_u32_max(delay);
if (!mod_delayed_work(mld_wq, &idev->mc_dad_work, tv + 2))
in6_dev_hold(idev);
@@ -1130,7 +1130,7 @@ static void igmp6_group_queried(struct ifmcaddr6 *ma, unsigned long resptime)
}
if (delay >= resptime)
- delay = prandom_u32() % resptime;
+ delay = prandom_u32_max(resptime);
if (!mod_delayed_work(mld_wq, &ma->mca_work, delay))
refcount_inc(&ma->mca_refcnt);
@@ -2574,7 +2574,7 @@ static void igmp6_join_group(struct ifmcaddr6 *ma)
igmp6_send(&ma->mca_addr, ma->idev->dev, ICMPV6_MGM_REPORT);
- delay = prandom_u32() % unsolicited_report_interval(ma->idev);
+ delay = prandom_u32_max(unsolicited_report_interval(ma->idev));
if (cancel_delayed_work(&ma->mca_work)) {
refcount_dec(&ma->mca_refcnt);