Re: [PATCH v1 2/5] treewide: use get_random_{u8,u16}() when possible
From: Kees Cook <hidden>
Date: 2022-10-06 06:29:03
Also in:
dri-devel, linux-f2fs-devel, linux-hams, linux-nvme, lvs-devel
On Wed, Oct 05, 2022 at 11:48:41PM +0200, Jason A. Donenfeld wrote:
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.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>Same question about "mechanism of transformation".
quoted hunk ↗ jump to hunk
diff --git a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c index ddfe9208529a..ac452a0111a9 100644 --- a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c +++ b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c@@ -1467,7 +1467,7 @@ static void make_established(struct sock *sk, u32 snd_isn, unsigned int opt) tp->write_seq = snd_isn; tp->snd_nxt = snd_isn; tp->snd_una = snd_isn; - inet_sk(sk)->inet_id = prandom_u32(); + inet_sk(sk)->inet_id = get_random_u16(); assign_rxopt(sk, opt); if (tp->rcv_wnd > (RCV_BUFSIZ_M << 10))
This one I had to go look at -- inet_id is u16, so yeah. :)
quoted hunk ↗ jump to hunk
diff --git a/lib/test_vmalloc.c b/lib/test_vmalloc.c index 56ffaa8dd3f6..0131ed2cd1bd 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.
This wasn't obvious either, but it looks like it's because it never consumes more than u8?
quoted hunk ↗ jump to hunk
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;
Yup, u16 off;
quoted hunk ↗ jump to hunk
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)) {
include/uapi/linux/pkt_sched.h:#define SFB_MAX_PROB 0xFFFF Reviewed-by: Kees Cook <redacted> -- Kees Cook