[PATCH v4 0/6] treewide cleanup of random integer usage

Jason A. Donenfeld
2022-10-07T18:01:01Z

Changes v3->v4:
- Split coccinelle mechanical step from non-mechanical step.
- Handle `get_random_int() & ~PAGE_MASK` -> `prandom_u32_max(PAGE_SIZE)`.

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, but the first step was split into two patches, the first of
which is cocinelle-able:

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 (6):
treewide: use prandom_u32_max() when possible, mechanically
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(-)

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2.37.3