Rather than truncate a 32-bit value to a 16-bit value or an 8-bit value, simply use the get_random_{u8,u16}() functions, which are faster than wasting the additional bytes from a 32-bit value. This was done by hand, identifying all of the places where one of the random integer functions was used in a non-32-bit context. Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> --- arch/s390/kernel/process.c | 2 +- lib/test_vmalloc.c | 2 +- net/ipv4/ip_output.c | 2 +- net/netfilter/nf_nat_core.c | 4 ++-- net/rds/bind.c | 2 +- net/sched/sch_sfb.c | 2 +- 6 files changed, 7 insertions(+), 7 deletions(-) diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c index 5ec78555dd2e..42af4b3aa02b 100644 --- a/arch/s390/kernel/process.c +++ b/arch/s390/kernel/process.c @@ -230,7 +230,7 @@ unsigned long arch_align_stack(unsigned long sp) static inline unsigned long brk_rnd(void) { - return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT; + return (get_random_u16() & BRK_RND_MASK) << PAGE_SHIFT; } unsigned long arch_randomize_brk(struct mm_struct *mm) diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c index a26bbbf20e62..cf7780572f5b 100644 --- a/lib/test_vmalloc.c +++ b/lib/test_vmalloc.c @@ -80,7 +80,7 @@ static int random_size_align_alloc_test(void) int i; for (i = 0; i < test_loop_count; i++) { - rnd = prandom_u32(); + rnd = get_random_u8(); /* * Maximum 1024 pages, if PAGE_SIZE is 4096. diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index 04e2034f2f8e..a4fbdbff14b3 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -172,7 +172,7 @@ int ip_build_and_send_pkt(struct sk_buff *skb, const struct sock *sk, * Avoid using the hashed IP ident generator. */ if (sk->sk_protocol == IPPROTO_TCP) - iph->id = (__force __be16)prandom_u32(); + iph->id = (__force __be16)get_random_u16(); else __ip_select_ident(net, iph, 1); } diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c index 7981be526f26..57c7686ac485 100644 --- a/net/netfilter/nf_nat_core.c +++ b/net/netfilter/nf_nat_core.c @@ -468,7 +468,7 @@ static void nf_nat_l4proto_unique_tuple(struct nf_conntrack_tuple *tuple, if (range->flags & NF_NAT_RANGE_PROTO_OFFSET) off = (ntohs(*keyptr) - ntohs(range->base_proto.all)); else - off = prandom_u32(); + off = get_random_u16(); attempts = range_size; if (attempts > max_attempts) @@ -490,7 +490,7 @@ static void nf_nat_l4proto_unique_tuple(struct nf_conntrack_tuple *tuple, if (attempts >= range_size || attempts < 16) return; attempts /= 2; - off = prandom_u32(); + off = get_random_u16(); goto another_round; } diff --git a/net/rds/bind.c b/net/rds/bind.c index 5b5fb4ca8d3e..97a29172a8ee 100644 --- a/net/rds/bind.c +++ b/net/rds/bind.c @@ -104,7 +104,7 @@ static int rds_add_bound(struct rds_sock *rs, const struct in6_addr *addr, return -EINVAL; last = rover; } else { - rover = max_t(u16, prandom_u32(), 2); + rover = max_t(u16, get_random_u16(), 2); last = rover - 1; } diff --git a/net/sched/sch_sfb.c b/net/sched/sch_sfb.c index 2829455211f8..7eb70acb4d58 100644 --- a/net/sched/sch_sfb.c +++ b/net/sched/sch_sfb.c @@ -379,7 +379,7 @@ static int sfb_enqueue(struct sk_buff *skb, struct Qdisc *sch, goto enqueue; } - r = prandom_u32() & SFB_MAX_PROB; + r = get_random_u16() & SFB_MAX_PROB; if (unlikely(r < p_min)) { if (unlikely(p_min > SFB_MAX_PROB / 2)) { -- 2.37.3