From 81895a65ec63ee1daec3255dc1a06675d2fbe915 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 5 Oct 2022 16:43:38 +0200 Subject: treewide: use prandom_u32_max() when possible, part 1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Kees Cook Reviewed-by: Yury Norov Reviewed-by: KP Singh Reviewed-by: Jan Kara # for ext4 and sbitmap Reviewed-by: Christoph Böhmwalder # for drbd Acked-by: Jakub Kicinski Acked-by: Heiko Carstens # for s390 Acked-by: Ulf Hansson # for mmc Acked-by: Darrick J. Wong # for xfs Signed-off-by: Jason A. Donenfeld --- net/core/neighbour.c | 2 +- net/core/pktgen.c | 43 +++++++++++++++++++++---------------------- net/core/stream.c | 2 +- 3 files changed, 23 insertions(+), 24 deletions(-) (limited to 'net/core') diff --git a/net/core/neighbour.c b/net/core/neighbour.c index e93edb810103..3c4786b99907 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -111,7 +111,7 @@ static void neigh_cleanup_and_release(struct neighbour *neigh) unsigned long neigh_rand_reach_time(unsigned long base) { - return base ? (prandom_u32() % base) + (base >> 1) : 0; + return base ? prandom_u32_max(base) + (base >> 1) : 0; } EXPORT_SYMBOL(neigh_rand_reach_time); diff --git a/net/core/pktgen.c b/net/core/pktgen.c index 88906ba6d9a7..5ca4f953034c 100644 --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -2324,7 +2324,7 @@ static inline int f_pick(struct pktgen_dev *pkt_dev) pkt_dev->curfl = 0; /*reset */ } } else { - flow = prandom_u32() % pkt_dev->cflows; + flow = prandom_u32_max(pkt_dev->cflows); pkt_dev->curfl = flow; if (pkt_dev->flows[flow].count > pkt_dev->lflow) { @@ -2380,10 +2380,9 @@ static void set_cur_queue_map(struct pktgen_dev *pkt_dev) else if (pkt_dev->queue_map_min <= pkt_dev->queue_map_max) { __u16 t; if (pkt_dev->flags & F_QUEUE_MAP_RND) { - t = prandom_u32() % - (pkt_dev->queue_map_max - - pkt_dev->queue_map_min + 1) - + pkt_dev->queue_map_min; + t = prandom_u32_max(pkt_dev->queue_map_max - + pkt_dev->queue_map_min + 1) + + pkt_dev->queue_map_min; } else { t = pkt_dev->cur_queue_map + 1; if (t > pkt_dev->queue_map_max) @@ -2412,7 +2411,7 @@ static void mod_cur_headers(struct pktgen_dev *pkt_dev) __u32 tmp; if (pkt_dev->flags & F_MACSRC_RND) - mc = prandom_u32() % pkt_dev->src_mac_count; + mc = prandom_u32_max(pkt_dev->src_mac_count); else { mc = pkt_dev->cur_src_mac_offset++; if (pkt_dev->cur_src_mac_offset >= @@ -2438,7 +2437,7 @@ static void mod_cur_headers(struct pktgen_dev *pkt_dev) __u32 tmp; if (pkt_dev->flags & F_MACDST_RND) - mc = prandom_u32() % pkt_dev->dst_mac_count; + mc = prandom_u32_max(pkt_dev->dst_mac_count); else { mc = pkt_dev->cur_dst_mac_offset++; @@ -2470,18 +2469,18 @@ static void mod_cur_headers(struct pktgen_dev *pkt_dev) } if ((pkt_dev->flags & F_VID_RND) && (pkt_dev->vlan_id != 0xffff)) { - pkt_dev->vlan_id = prandom_u32() & (4096 - 1); + pkt_dev->vlan_id = prandom_u32_max(4096); } if ((pkt_dev->flags & F_SVID_RND) && (pkt_dev->svlan_id != 0xffff)) { - pkt_dev->svlan_id = prandom_u32() & (4096 - 1); + pkt_dev->svlan_id = prandom_u32_max(4096); } if (pkt_dev->udp_src_min < pkt_dev->udp_src_max) { if (pkt_dev->flags & F_UDPSRC_RND) - pkt_dev->cur_udp_src = prandom_u32() % - (pkt_dev->udp_src_max - pkt_dev->udp_src_min) - + pkt_dev->udp_src_min; + pkt_dev->cur_udp_src = prandom_u32_max( + pkt_dev->udp_src_max - pkt_dev->udp_src_min) + + pkt_dev->udp_src_min; else { pkt_dev->cur_udp_src++; @@ -2492,9 +2491,9 @@ static void mod_cur_headers(struct pktgen_dev *pkt_dev) if (pkt_dev->udp_dst_min < pkt_dev->udp_dst_max) { if (pkt_dev->flags & F_UDPDST_RND) { - pkt_dev->cur_udp_dst = prandom_u32() % - (pkt_dev->udp_dst_max - pkt_dev->udp_dst_min) - + pkt_dev->udp_dst_min; + pkt_dev->cur_udp_dst = prandom_u32_max( + pkt_dev->udp_dst_max - pkt_dev->udp_dst_min) + + pkt_dev->udp_dst_min; } else { pkt_dev->cur_udp_dst++; if (pkt_dev->cur_udp_dst >= pkt_dev->udp_dst_max) @@ -2509,7 +2508,7 @@ static void mod_cur_headers(struct pktgen_dev *pkt_dev) if (imn < imx) { __u32 t; if (pkt_dev->flags & F_IPSRC_RND) - t = prandom_u32() % (imx - imn) + imn; + t = prandom_u32_max(imx - imn) + imn; else { t = ntohl(pkt_dev->cur_saddr); t++; @@ -2531,8 +2530,8 @@ static void mod_cur_headers(struct pktgen_dev *pkt_dev) if (pkt_dev->flags & F_IPDST_RND) { do { - t = prandom_u32() % - (imx - imn) + imn; + t = prandom_u32_max(imx - imn) + + imn; s = htonl(t); } while (ipv4_is_loopback(s) || ipv4_is_multicast(s) || @@ -2579,9 +2578,9 @@ static void mod_cur_headers(struct pktgen_dev *pkt_dev) if (pkt_dev->min_pkt_size < pkt_dev->max_pkt_size) { __u32 t; if (pkt_dev->flags & F_TXSIZE_RND) { - t = prandom_u32() % - (pkt_dev->max_pkt_size - pkt_dev->min_pkt_size) - + pkt_dev->min_pkt_size; + t = prandom_u32_max(pkt_dev->max_pkt_size - + pkt_dev->min_pkt_size) + + pkt_dev->min_pkt_size; } else { t = pkt_dev->cur_pkt_size + 1; if (t > pkt_dev->max_pkt_size) @@ -2590,7 +2589,7 @@ static void mod_cur_headers(struct pktgen_dev *pkt_dev) pkt_dev->cur_pkt_size = t; } else if (pkt_dev->n_imix_entries > 0) { struct imix_pkt *entry; - __u32 t = prandom_u32() % IMIX_PRECISION; + __u32 t = prandom_u32_max(IMIX_PRECISION); __u8 entry_index = pkt_dev->imix_distribution[t]; entry = &pkt_dev->imix_entries[entry_index]; diff --git a/net/core/stream.c b/net/core/stream.c index 1105057ce00a..75fded8495f5 100644 --- a/net/core/stream.c +++ b/net/core/stream.c @@ -123,7 +123,7 @@ int sk_stream_wait_memory(struct sock *sk, long *timeo_p) DEFINE_WAIT_FUNC(wait, woken_wake_function); if (sk_stream_memory_free(sk)) - current_timeo = vm_wait = (prandom_u32() % (HZ / 5)) + 2; + current_timeo = vm_wait = prandom_u32_max(HZ / 5) + 2; add_wait_queue(sk_sleep(sk), &wait); -- cgit v1.2.3-59-g8ed1b