| Message ID | 20221006165346.73159-1-Jason@zx2c4.com |
|---|---|
| Headers | show |
| Series | treewide cleanup of random integer usage | expand |
From: Jason A. Donenfeld > Sent: 07 October 2022 18:56 ... > > Given these kinds of less mechanical changes, it may make sense to split > > these from the "trivial" conversions in a treewide patch. The chance of > > needing a revert from the simple 1:1 conversions is much lower than the > > need to revert by-hand changes. > > > > The Cocci script I suggested in my v1 review gets 80% of the first > > patch, for example. > > I'll split things up into a mechanical step and a non-mechanical step. > Good idea. I'd also do something about the 'get_random_int() & 3' cases. (ie remainder by 2^n-1) These can be converted to 'get_random_u8() & 3' (etc). So they only need one random byte (not 4) and no multiply. Possibly something based on (the quickly typed, and not C): #define get_random_below(val) [ if (builtin_constant(val)) BUILD_BUG_ON(!val || val > 0x100000000ull) if (!(val & (val - 1)) { if (val <= 0x100) return get_random_u8() & (val - 1); if (val <= 0x10000) return get_random_u16() & (val - 1); return get_random_u32() & (val - 1); } } BUILD_BUG_ON(sizeof (val) > 4); return ((u64)get_random_u32() * val) >> 32; } get_random_below() is a much better name than prandom_u32_max(). David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
On Sat, Oct 08, 2022 at 09:53:33PM +0000, David Laight wrote: > From: Jason A. Donenfeld > > Sent: 07 October 2022 18:56 > ... > > > Given these kinds of less mechanical changes, it may make sense to split > > > these from the "trivial" conversions in a treewide patch. The chance of > > > needing a revert from the simple 1:1 conversions is much lower than the > > > need to revert by-hand changes. > > > > > > The Cocci script I suggested in my v1 review gets 80% of the first > > > patch, for example. > > > > I'll split things up into a mechanical step and a non-mechanical step. > > Good idea. > > I'd also do something about the 'get_random_int() & 3' cases. > (ie remainder by 2^n-1) > These can be converted to 'get_random_u8() & 3' (etc). > So they only need one random byte (not 4) and no multiply. > > Possibly something based on (the quickly typed, and not C): > #define get_random_below(val) [ > if (builtin_constant(val)) > BUILD_BUG_ON(!val || val > 0x100000000ull) > if (!(val & (val - 1)) { > if (val <= 0x100) > return get_random_u8() & (val - 1); > if (val <= 0x10000) > return get_random_u16() & (val - 1); > return get_random_u32() & (val - 1); > } > } > BUILD_BUG_ON(sizeof (val) > 4); > return ((u64)get_random_u32() * val) >> 32; This is already how the prandom_u32_max() implementation works, as suggested in the cover letter. The multiplication by constants in it reduces to bit shifts and you already get all the manual masking possible. > get_random_below() is a much better name than prandom_u32_max(). Yes, but that name is reserved for when I succeed at making a function that bounds with a uniform distribution. prandom_u32_max()'s distribution is non-uniform since it doesn't do rejection sampling. Work in progress is on https://git.zx2c4.com/linux-rng/commit/?h=jd/get_random_u32_below . But out of common respect for this already huge thread with a massive CC list, if you want to bikeshed my WIP stuff, please start a new thread for that and not bog this one down. IOW, no need to reply here directly. That'd annoy me. Jason
Changes v2->v3: - Handle get_random_int() conversions too, which were overlooked before, in the same way as the rest. Hi folks, This is a five part treewide cleanup of random integer handling. The rules for random integers are: - If you want a secure or an insecure random u64, use get_random_u64(). - If you want a secure or an insecure random u32, use get_random_u32(). * The old function prandom_u32() has been deprecated for a while now and is just a wrapper around get_random_u32(). Same for get_random_int(). - If you want a secure or an insecure random u16, use get_random_u16(). - If you want a secure or an insecure random u8, use get_random_u8(). - If you want secure or insecure random bytes, use get_random_bytes(). * The old function prandom_bytes() has been deprecated for a while now and has long been a wrapper around get_random_bytes(). - If you want a non-uniform random u32, u16, or u8 bounded by a certain open interval maximum, use prandom_u32_max(). * I say "non-uniform", because it doesn't do any rejection sampling or divisions. Hence, it stays within the prandom_* namespace. These rules ought to be applied uniformly, so that we can clean up the deprecated functions, and earn the benefits of using the modern functions. In particular, in addition to the boring substitutions, this patchset accomplishes a few nice effects: - By using prandom_u32_max() with an upper-bound that the compiler can prove at compile-time is ≤65536 or ≤256, internally get_random_u16() or get_random_u8() is used, which wastes fewer batched random bytes, and hence has higher throughput. - By using prandom_u32_max() instead of %, when the upper-bound is not a constant, division is still avoided, because prandom_u32_max() uses a faster multiplication-based trick instead. - By using get_random_u16() or get_random_u8() in cases where the return value is intended to indeed be a u16 or a u8, we waste fewer batched random bytes, and hence have higher throughput. So, based on those rules and benefits from following them, this patchset breaks down into the following five steps, which were done mostly manually: 1) Replace `prandom_u32() % max` and variants thereof with prandom_u32_max(max). 2) Replace `(type)get_random_u32()` and variants thereof with get_random_u16() or get_random_u8(). I took the pains to actually look and see what every lvalue type was across the entire tree. 3) Replace remaining deprecated uses of prandom_u32() and get_random_int() with get_random_u32(). 4) Replace remaining deprecated uses of prandom_bytes() with get_random_bytes(). 5) Remove the deprecated and now-unused prandom_u32() and prandom_bytes() inline wrapper functions. I was thinking of taking this through my random.git tree (on which this series is currently based) and submitting it near the end of the merge window, or waiting for the very end of the 6.1 cycle when there will be the fewest new patches brewing. If somebody with some treewide-cleanup experience might share some wisdom about what the best timing usually winds up being, I'm all ears. Please take a look! At "379 insertions(+), 422 deletions(-)", this should be a somewhat small patchset to review, despite it having the scary "treewide" moniker on it. Thanks, Jason Cc: Andreas Noever <andreas.noever@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Dave Airlie <airlied@redhat.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David S. Miller <davem@davemloft.net> Cc: Eric Dumazet <edumazet@google.com> Cc: Florian Westphal <fw@strlen.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Cc: H. Peter Anvin <hpa@zytor.com> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Helge Deller <deller@gmx.de> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Huacai Chen <chenhuacai@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Jakub Kicinski <kuba@kernel.org> Cc: James E.J. Bottomley <jejb@linux.ibm.com> Cc: Jan Kara <jack@suse.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: Jens Axboe <axboe@kernel.dk> Cc: Johannes Berg <johannes@sipsolutions.net> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Jozsef Kadlecsik <kadlec@netfilter.org> Cc: KP Singh <kpsingh@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Marco Elver <elver@google.com> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Pablo Neira Ayuso <pablo@netfilter.org> Cc: Paolo Abeni <pabeni@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Richard Weinberger <richard@nod.at> Cc: Russell King <linux@armlinux.org.uk> Cc: Theodore Ts'o <tytso@mit.edu> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Thomas Graf <tgraf@suug.ch> Cc: Ulf Hansson <ulf.hansson@linaro.org> Cc: Vignesh Raghavendra <vigneshr@ti.com> Cc: WANG Xuerui <kernel@xen0n.name> Cc: Will Deacon <will@kernel.org> Cc: Yury Norov <yury.norov@gmail.com> Cc: dri-devel@lists.freedesktop.org Cc: kasan-dev@googlegroups.com Cc: kernel-janitors@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-block@vger.kernel.org Cc: linux-crypto@vger.kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-media@vger.kernel.org Cc: linux-mips@vger.kernel.org Cc: linux-mm@kvack.org Cc: linux-mmc@vger.kernel.org Cc: linux-mtd@lists.infradead.org Cc: linux-nvme@lists.infradead.org Cc: linux-parisc@vger.kernel.org Cc: linux-rdma@vger.kernel.org Cc: linux-s390@vger.kernel.org Cc: linux-um@lists.infradead.org Cc: linux-usb@vger.kernel.org Cc: linux-wireless@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: loongarch@lists.linux.dev Cc: netdev@vger.kernel.org Cc: sparclinux@vger.kernel.org Cc: x86@kernel.org Jason A. Donenfeld (5): treewide: use prandom_u32_max() when possible treewide: use get_random_{u8,u16}() when possible treewide: use get_random_u32() when possible treewide: use get_random_bytes when possible prandom: remove unused functions Documentation/networking/filter.rst | 2 +- arch/arm/kernel/process.c | 2 +- arch/arm/kernel/signal.c | 2 +- arch/arm64/kernel/process.c | 2 +- arch/arm64/kernel/syscall.c | 2 +- arch/loongarch/kernel/process.c | 2 +- arch/loongarch/kernel/vdso.c | 2 +- arch/mips/kernel/process.c | 2 +- arch/mips/kernel/vdso.c | 2 +- arch/parisc/kernel/process.c | 2 +- arch/parisc/kernel/sys_parisc.c | 4 +- arch/parisc/kernel/vdso.c | 2 +- arch/powerpc/crypto/crc-vpmsum_test.c | 2 +- arch/powerpc/kernel/process.c | 2 +- arch/s390/kernel/process.c | 4 +- arch/s390/kernel/vdso.c | 2 +- arch/s390/mm/mmap.c | 2 +- arch/sparc/vdso/vma.c | 2 +- arch/um/kernel/process.c | 2 +- arch/x86/entry/vdso/vma.c | 2 +- arch/x86/kernel/cpu/amd.c | 2 +- arch/x86/kernel/module.c | 2 +- arch/x86/kernel/process.c | 2 +- arch/x86/mm/pat/cpa-test.c | 4 +- block/blk-crypto-fallback.c | 2 +- crypto/async_tx/raid6test.c | 2 +- crypto/testmgr.c | 94 +++++++++---------- drivers/block/drbd/drbd_receiver.c | 4 +- drivers/char/random.c | 11 +-- drivers/dma/dmatest.c | 2 +- .../gpu/drm/i915/gem/i915_gem_execbuffer.c | 2 +- drivers/gpu/drm/i915/i915_gem_gtt.c | 6 +- .../gpu/drm/i915/selftests/i915_selftest.c | 2 +- drivers/gpu/drm/selftests/test-drm_buddy.c | 2 +- drivers/gpu/drm/selftests/test-drm_mm.c | 2 +- drivers/infiniband/core/cma.c | 2 +- drivers/infiniband/hw/cxgb4/cm.c | 4 +- drivers/infiniband/hw/cxgb4/id_table.c | 4 +- drivers/infiniband/hw/hfi1/tid_rdma.c | 2 +- drivers/infiniband/hw/hns/hns_roce_ah.c | 5 +- drivers/infiniband/hw/mlx4/mad.c | 2 +- drivers/infiniband/ulp/ipoib/ipoib_cm.c | 2 +- drivers/infiniband/ulp/rtrs/rtrs-clt.c | 3 +- drivers/md/bcache/request.c | 2 +- drivers/md/raid5-cache.c | 2 +- drivers/media/common/v4l2-tpg/v4l2-tpg-core.c | 2 +- .../media/test-drivers/vivid/vivid-radio-rx.c | 4 +- .../test-drivers/vivid/vivid-touch-cap.c | 6 +- drivers/misc/habanalabs/gaudi2/gaudi2.c | 2 +- drivers/mmc/core/core.c | 4 +- drivers/mmc/host/dw_mmc.c | 2 +- drivers/mtd/nand/raw/nandsim.c | 8 +- drivers/mtd/tests/mtd_nandecctest.c | 12 +-- drivers/mtd/tests/speedtest.c | 2 +- drivers/mtd/tests/stresstest.c | 19 +--- drivers/mtd/ubi/debug.c | 2 +- drivers/mtd/ubi/debug.h | 6 +- drivers/net/bonding/bond_main.c | 2 +- drivers/net/ethernet/broadcom/bnxt/bnxt.c | 2 +- drivers/net/ethernet/broadcom/cnic.c | 5 +- .../chelsio/inline_crypto/chtls/chtls_cm.c | 4 +- .../chelsio/inline_crypto/chtls/chtls_io.c | 4 +- drivers/net/ethernet/rocker/rocker_main.c | 8 +- drivers/net/hamradio/baycom_epp.c | 2 +- drivers/net/hamradio/hdlcdrv.c | 2 +- drivers/net/hamradio/yam.c | 2 +- drivers/net/phy/at803x.c | 2 +- drivers/net/wireguard/selftest/allowedips.c | 16 ++-- .../broadcom/brcm80211/brcmfmac/p2p.c | 2 +- .../broadcom/brcm80211/brcmfmac/pno.c | 2 +- .../net/wireless/intel/iwlwifi/mvm/mac-ctxt.c | 2 +- .../net/wireless/marvell/mwifiex/cfg80211.c | 4 +- .../wireless/microchip/wilc1000/cfg80211.c | 2 +- .../net/wireless/quantenna/qtnfmac/cfg80211.c | 2 +- drivers/net/wireless/st/cw1200/wsm.c | 2 +- drivers/net/wireless/ti/wlcore/main.c | 2 +- drivers/nvme/common/auth.c | 2 +- drivers/scsi/cxgbi/cxgb4i/cxgb4i.c | 4 +- drivers/scsi/fcoe/fcoe_ctlr.c | 4 +- drivers/scsi/lpfc/lpfc_hbadisc.c | 6 +- drivers/scsi/qedi/qedi_main.c | 2 +- drivers/target/iscsi/cxgbit/cxgbit_cm.c | 2 +- drivers/thunderbolt/xdomain.c | 2 +- drivers/video/fbdev/uvesafb.c | 2 +- fs/ceph/inode.c | 2 +- fs/ceph/mdsmap.c | 2 +- fs/exfat/inode.c | 2 +- fs/ext2/ialloc.c | 3 +- fs/ext4/ialloc.c | 7 +- fs/ext4/ioctl.c | 4 +- fs/ext4/mmp.c | 2 +- fs/ext4/super.c | 7 +- fs/f2fs/gc.c | 2 +- fs/f2fs/namei.c | 2 +- fs/f2fs/segment.c | 8 +- fs/fat/inode.c | 2 +- fs/nfsd/nfs4state.c | 4 +- fs/ntfs3/fslog.c | 6 +- fs/ubifs/debug.c | 10 +- fs/ubifs/journal.c | 2 +- fs/ubifs/lpt_commit.c | 14 +-- fs/ubifs/tnc_commit.c | 2 +- fs/xfs/libxfs/xfs_alloc.c | 2 +- fs/xfs/libxfs/xfs_ialloc.c | 4 +- fs/xfs/xfs_error.c | 2 +- fs/xfs/xfs_icache.c | 2 +- fs/xfs/xfs_log.c | 2 +- include/linux/nodemask.h | 2 +- include/linux/prandom.h | 12 --- include/linux/random.h | 5 - include/net/netfilter/nf_queue.h | 2 +- include/net/red.h | 2 +- include/net/sock.h | 2 +- kernel/bpf/bloom_filter.c | 2 +- kernel/bpf/core.c | 6 +- kernel/bpf/hashtab.c | 2 +- kernel/bpf/verifier.c | 2 +- kernel/kcsan/selftest.c | 4 +- kernel/locking/test-ww_mutex.c | 4 +- kernel/time/clocksource.c | 2 +- lib/cmdline_kunit.c | 4 +- lib/fault-inject.c | 2 +- lib/find_bit_benchmark.c | 4 +- lib/kobject.c | 2 +- lib/random32.c | 4 +- lib/reed_solomon/test_rslib.c | 12 +-- lib/sbitmap.c | 4 +- lib/test-string_helpers.c | 2 +- lib/test_fprobe.c | 2 +- lib/test_hexdump.c | 10 +- lib/test_kasan.c | 6 +- lib/test_kprobes.c | 2 +- lib/test_list_sort.c | 2 +- lib/test_min_heap.c | 6 +- lib/test_objagg.c | 2 +- lib/test_rhashtable.c | 6 +- lib/test_vmalloc.c | 19 +--- lib/uuid.c | 2 +- mm/migrate.c | 2 +- mm/shmem.c | 2 +- mm/slab.c | 2 +- mm/slub.c | 2 +- net/802/garp.c | 2 +- net/802/mrp.c | 2 +- net/ceph/mon_client.c | 2 +- net/ceph/osd_client.c | 2 +- net/core/neighbour.c | 2 +- net/core/pktgen.c | 47 +++++----- net/core/stream.c | 2 +- net/dccp/ipv4.c | 4 +- net/ipv4/datagram.c | 2 +- net/ipv4/igmp.c | 6 +- net/ipv4/inet_connection_sock.c | 2 +- net/ipv4/inet_hashtables.c | 2 +- net/ipv4/ip_output.c | 2 +- net/ipv4/route.c | 4 +- net/ipv4/tcp_cdg.c | 2 +- net/ipv4/tcp_ipv4.c | 4 +- net/ipv4/udp.c | 2 +- net/ipv6/addrconf.c | 8 +- net/ipv6/ip6_flowlabel.c | 2 +- net/ipv6/mcast.c | 10 +- net/ipv6/output_core.c | 2 +- net/mac80211/rc80211_minstrel_ht.c | 2 +- net/mac80211/scan.c | 2 +- net/netfilter/ipvs/ip_vs_conn.c | 2 +- net/netfilter/ipvs/ip_vs_twos.c | 4 +- net/netfilter/nf_nat_core.c | 4 +- net/netfilter/xt_statistic.c | 2 +- net/openvswitch/actions.c | 2 +- net/packet/af_packet.c | 2 +- net/rds/bind.c | 2 +- net/sched/act_gact.c | 2 +- net/sched/act_sample.c | 2 +- net/sched/sch_cake.c | 8 +- net/sched/sch_netem.c | 22 ++--- net/sched/sch_pie.c | 2 +- net/sched/sch_sfb.c | 2 +- net/sctp/socket.c | 4 +- net/sunrpc/auth_gss/gss_krb5_wrap.c | 4 +- net/sunrpc/cache.c | 2 +- net/sunrpc/xprt.c | 2 +- net/sunrpc/xprtsock.c | 2 +- net/tipc/socket.c | 2 +- net/unix/af_unix.c | 2 +- net/xfrm/xfrm_state.c | 2 +- 186 files changed, 379 insertions(+), 422 deletions(-)