In tls_init(), a write memory barrier is missing, and store-store
reordering may cause NULL dereference in tls_{setsockopt,getsockopt}.
CPU0 CPU1
----- -----
// In tls_init()
// In tls_ctx_create()
ctx = kzalloc()
ctx->sk_proto = READ_ONCE(sk->sk_prot) -(1)
// In update_sk_prot()
WRITE_ONCE(sk->sk_prot, tls_prots) -(2)
// In sock_common_setsockopt()
READ_ONCE(sk->sk_prot)->setsockopt()
// In tls_{setsockopt,getsockopt}()
ctx->sk_proto->setsockopt() -(3)
In the above scenario, when (1) and (2) are reordered, (3) can observe
the NULL value of ctx->sk_proto, causing NULL dereference.
To fix it, we rely on rcu_assign_pointer() which implies the release
barrier semantic. By moving rcu_assign_pointer() after ctx->sk_proto is
initialized, we can ensure that ctx->sk_proto are visible when
changing sk->sk_prot.
Fixes: d5bee7374b ("net/tls: Annotate access to sk_prot with READ_ONCE/WRITE_ONCE")
Signed-off-by: Yewon Choi <woni9911@gmail.com>
Signed-off-by: Dae R. Jeong <threeearcat@gmail.com>
Link: https://lore.kernel.org/netdev/ZU4OJG56g2V9z_H7@dragonet/T/
Link: https://lore.kernel.org/r/Zkx4vjSFp0mfpjQ2@libra05
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Since the introduction of the subflow ULP diag interface, the
dump callback accessed all the subflow data with lockless.
We need either to annotate all the read and write operation accordingly,
or acquire the subflow socket lock. Let's do latter, even if slower, to
avoid a diffstat havoc.
Fixes: 5147dfb508 ("mptcp: allow dumping subflow context to userspace")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
As reported by Tom, .NET and applications build on top of it rely
on connect(AF_UNSPEC) to async cancel pending I/O operations on TCP
socket.
The blamed commit below caused a regression, as such cancellation
can now fail.
As suggested by Eric, this change addresses the problem explicitly
causing blocking I/O operation to terminate immediately (with an error)
when a concurrent disconnect() is executed.
Instead of tracking the number of threads blocked on a given socket,
track the number of disconnect() issued on such socket. If such counter
changes after a blocking operation releasing and re-acquiring the socket
lock, error out the current operation.
Fixes: 4faeee0cf8 ("tcp: deny tcp_disconnect() when threads are waiting")
Reported-by: Tom Deseyn <tdeseyn@redhat.com>
Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1886305
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/f3b95e47e3dbed840960548aebaa8d954372db41.1697008693.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
It's not really needed since we end up refetching it as tls_ctx. We
can also remove the NULL check, since we have already dereferenced ctx
in do_tls_setsockopt_conf.
While at it, fix up the reverse xmas tree ordering.
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
It's not really needed since we end up refetching it as tls_ctx. We
can also remove the NULL check, since we have already dereferenced ctx
in do_tls_setsockopt_conf.
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
TLS_MAX_IV_SIZE + TLS_MAX_SALT_SIZE is 20B, we don't get much benefit
in cipher_context's size and can simplify the init code a bit.
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
It's defined in include/net/tls.h, avoid using an overly generic name.
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
TLS_MAX_REC_SEQ_SIZE is 8B, we don't get anything by using kmalloc.
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Every cipher uses the same code to update its crypto_info struct based
on the values contained in the cctx, with only the struct type and
size/offset changing. We can get those from tls_cipher_desc, and use
a single pair of memcpy and final copy_to_user.
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://lore.kernel.org/r/c21a904b91e972bdbbf9d1c6d2731ccfa1eedf72.1692977948.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
- add nonce, usually equal to iv_size but not for chacha
- add offsets into the crypto_info for each field
- add algorithm name
- add offloadable flag
Also add helpers to access each field of a crypto_info struct
described by a tls_cipher_desc.
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://lore.kernel.org/r/39d5f476d63c171097764e8d38f6f158b7c109ae.1692977948.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
tls_cipher_size_desc indexes ciphers by their type, but we're not
using indices 0..50 of the array. Each struct tls_cipher_size_desc is
20B, so that's a lot of unused memory. We can reindex the array
starting at the lowest used cipher_type.
Introduce the get_cipher_size_desc helper to find the right item and
avoid out-of-bounds accesses, and make tls_cipher_size_desc's size
explicit so that gcc reminds us to update TLS_CIPHER_MIN/MAX when we
add a new cipher.
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://lore.kernel.org/r/5e054e370e240247a5d37881a1cd93a67c15f4ca.1692977948.git.sd@queasysnail.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
We used to change the flags for the last segment, because
non-last segments had the MSG_SENDPAGE_NOTLAST flag set.
That flag is no longer a thing so remove the setting.
Since flags most likely don't have MSG_SPLICE_PAGES set
this avoids passing parts of the sg as splice and parts
as non-splice. Before commit under Fixes we'd have called
tcp_sendpage() which would add the MSG_SPLICE_PAGES.
Why this leads to trouble remains unclear but Tariq
reports hitting the WARN_ON(!sendpage_ok()) due to
page refcount of 0.
Fixes: e117dcfd64 ("tls: Inline do_tcp_sendpages()")
Reported-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/all/4c49176f-147a-4283-f1b1-32aac7b4b996@gmail.com/
Tested-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/r/20230808180917.1243540-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Implement ->read_sock() function for use with nvme-tcp.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Cc: Boris Pismenny <boris.pismenny@gmail.com>
Link: https://lore.kernel.org/r/20230726191556.41714-7-hare@suse.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Allow splice to end a TLS record after prematurely ending a splice/sendfile
due to getting an EOF condition (->splice_read() returned 0) after splice
had called TLS with a sendmsg() with MSG_MORE set when the user didn't set
MSG_MORE.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/CAHk-=wh=V579PDYvkpnTobCLGczbgxpMgGmmhqiTyE34Cpi5Gg@mail.gmail.com/
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
cc: Chuck Lever <chuck.lever@oracle.com>
cc: Boris Pismenny <borisp@nvidia.com>
cc: John Fastabend <john.fastabend@gmail.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Allow splice to end a TLS record after prematurely ending a splice/sendfile
due to getting an EOF condition (->splice_read() returned 0) after splice
had called TLS with a sendmsg() with MSG_MORE set when the user didn't set
MSG_MORE.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/CAHk-=wh=V579PDYvkpnTobCLGczbgxpMgGmmhqiTyE34Cpi5Gg@mail.gmail.com/
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
cc: Chuck Lever <chuck.lever@oracle.com>
cc: Boris Pismenny <borisp@nvidia.com>
cc: John Fastabend <john.fastabend@gmail.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
TLS does not override .poll() so TLS-enabled socket will generate
an event whenever data arrives at the TCP socket. This leads to
unnecessary wakeups on slow connections.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
do_tcp_sendpages() is now just a small wrapper around tcp_sendmsg_locked(),
so inline it, allowing do_tcp_sendpages() to be removed. This is part of
replacing ->sendpage() with a call to sendmsg() with MSG_SPLICE_PAGES set.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Boris Pismenny <borisp@nvidia.com>
cc: John Fastabend <john.fastabend@gmail.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
__condition is evaluated twice in sk_wait_event() macro.
First invocation is lockless, and reads can race with writes,
as spotted by syzbot.
BUG: KCSAN: data-race in sk_stream_wait_connect / tcp_disconnect
write to 0xffff88812d83d6a0 of 4 bytes by task 9065 on cpu 1:
tcp_disconnect+0x2cd/0xdb0
inet_shutdown+0x19e/0x1f0 net/ipv4/af_inet.c:911
__sys_shutdown_sock net/socket.c:2343 [inline]
__sys_shutdown net/socket.c:2355 [inline]
__do_sys_shutdown net/socket.c:2363 [inline]
__se_sys_shutdown+0xf8/0x140 net/socket.c:2361
__x64_sys_shutdown+0x31/0x40 net/socket.c:2361
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
read to 0xffff88812d83d6a0 of 4 bytes by task 9040 on cpu 0:
sk_stream_wait_connect+0x1de/0x3a0 net/core/stream.c:75
tcp_sendmsg_locked+0x2e4/0x2120 net/ipv4/tcp.c:1266
tcp_sendmsg+0x30/0x50 net/ipv4/tcp.c:1484
inet6_sendmsg+0x63/0x80 net/ipv6/af_inet6.c:651
sock_sendmsg_nosec net/socket.c:724 [inline]
sock_sendmsg net/socket.c:747 [inline]
__sys_sendto+0x246/0x300 net/socket.c:2142
__do_sys_sendto net/socket.c:2154 [inline]
__se_sys_sendto net/socket.c:2150 [inline]
__x64_sys_sendto+0x78/0x90 net/socket.c:2150
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
value changed: 0x00000000 -> 0x00000068
Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
ctx->crypto_send.info is not protected by lock_sock in
do_tls_getsockopt_conf(). A race condition between do_tls_getsockopt_conf()
and error paths of do_tls_setsockopt_conf() may lead to a use-after-free
or null-deref.
More discussion: https://lore.kernel.org/all/Y/ht6gQL+u6fj3dG@hog/
Fixes: 3c4d755915 ("tls: kernel TLS support")
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Link: https://lore.kernel.org/r/20230228023344.9623-1-hbh25y@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Introduce cipher sizes descriptor. It helps reducing the amount of code
duplications and repeated switch/cases that assigns the proper sizes
according to the cipher type.
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Gal Pressman <gal@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
TLS is a relatively poor fit for strparser. We pause the input
every time a message is received, wait for a read which will
decrypt the message, start the parser, repeat. strparser is
built to delineate the messages, wrap them in individual skbs
and let them float off into the stack or a different socket.
TLS wants the data pages and nothing else. There's no need
for TLS to keep cloning (and occasionally skb_unclone()'ing)
the TCP rx queue.
This patch uses a pre-allocated skb and attaches the skbs
from the TCP rx queue to it as frags. TLS is careful never
to modify the input skb without CoW'ing / detaching it first.
Since we call TCP rx queue cleanup directly we also get back
the benefit of skb deferred free.
Overall this results in a 6% gain in my benchmarks.
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
include/net/tls.h is getting a little long, and is probably hard
for driver authors to navigate. Split out the internals into a
header which will live under net/tls/. While at it move some
static inlines with a single user into the source files, add
a few tls_ prefixes and fix spelling of 'proccess'.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Since optimisitic decrypt may add extra load in case of retries
require socket owner to explicitly opt-in.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Commit 8a59f9d1e3 ("sock: Introduce sk->sk_prot->psock_update_sk_prot()")
has moved the inet_csk_has_ulp(sk) check from sk_psock_init() to
the new tcp_bpf_update_proto() function. I'm guessing that this
was done to allow creating psocks for non-inet sockets.
Unfortunately the destruction path for psock includes the ULP
unwind, so we need to fail the sk_psock_init() itself.
Otherwise if ULP is already present we'll notice that later,
and call tcp_update_ulp() with the sk_proto of the ULP
itself, which will most likely result in the ULP looping
its callbacks.
Fixes: 8a59f9d1e3 ("sock: Introduce sk->sk_prot->psock_update_sk_prot()")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Tested-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/r/20220620191353.1184629-2-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This reverts commit 69135c572d.
This commit was just papering over the issue, ULP should not
get ->update() called with its own sk_prot. Each ULP would
need to add this check.
Fixes: 69135c572d ("net/tls: fix tls_sk_proto_close executed repeatedly")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20220620191353.1184629-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
After setting the sock ktls, update ctx->sk_proto to sock->sk_prot by
tls_update(), so now ctx->sk_proto->close is tls_sk_proto_close(). When
close the sock, tls_sk_proto_close() is called for sock->sk_prot->close
is tls_sk_proto_close(). But ctx->sk_proto->close() will be executed later
in tls_sk_proto_close(). Thus tls_sk_proto_close() executed repeatedly
occurred. That will trigger the following bug.
=================================================================
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
RIP: 0010:tls_sk_proto_close+0xd8/0xaf0 net/tls/tls_main.c:306
Call Trace:
<TASK>
tls_sk_proto_close+0x356/0xaf0 net/tls/tls_main.c:329
inet_release+0x12e/0x280 net/ipv4/af_inet.c:428
__sock_release+0xcd/0x280 net/socket.c:650
sock_close+0x18/0x20 net/socket.c:1365
Updating a proto which is same with sock->sk_prot is incorrect. Add proto
and sock->sk_prot equality check at the head of tls_update() to fix it.
Fixes: 95fa145479 ("bpf: sockmap/tls, close can race with map free")
Reported-by: syzbot+29c3c12f3214b85ad081@syzkaller.appspotmail.com
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
To embrace possible future optimizations of TLS, rename zerocopy
sendfile definitions to more generic ones:
* setsockopt: TLS_TX_ZEROCOPY_SENDFILE- > TLS_TX_ZEROCOPY_RO
* sock_diag: TLS_INFO_ZC_SENDFILE -> TLS_INFO_ZC_RO_TX
RO stands for readonly and emphasizes that the application shouldn't
modify the data being transmitted with zerocopy to avoid potential
disconnection.
Fixes: c1318b39c7 ("tls: Add opt-in zerocopy mode of sendfile()")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Link: https://lore.kernel.org/r/20220608153425.3151146-1-maximmi@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
TLS device offload copies sendfile data to a bounce buffer before
transmitting. It allows to maintain the valid MAC on TLS records when
the file contents change and a part of TLS record has to be
retransmitted on TCP level.
In many common use cases (like serving static files over HTTPS) the file
contents are not changed on the fly. In many use cases breaking the
connection is totally acceptable if the file is changed during
transmission, because it would be received corrupted in any case.
This commit allows to optimize performance for such use cases to
providing a new optional mode of TLS sendfile(), in which the extra copy
is skipped. Removing this copy improves performance significantly, as
TLS and TCP sendfile perform the same operations, and the only overhead
is TLS header/trailer insertion.
The new mode can only be enabled with the new socket option named
TLS_TX_ZEROCOPY_SENDFILE on per-socket basis. It preserves backwards
compatibility with existing applications that rely on the copying
behavior.
The new mode is safe, meaning that unsolicited modifications of the file
being sent can't break integrity of the kernel. The worst thing that can
happen is sending a corrupted TLS record, which is in any case not
forbidden when using regular TCP sockets.
Sockets other than TLS device offload are not affected by the new socket
option. The actual status of zerocopy sendfile can be queried with
sock_diag.
Performance numbers in a single-core test with 24 HTTPS streams on
nginx, under 100% CPU load:
* non-zerocopy: 33.6 Gbit/s
* zerocopy: 79.92 Gbit/s
CPU: Intel(R) Xeon(R) Platinum 8380 CPU @ 2.30GHz
Signed-off-by: Boris Pismenny <borisp@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20220518092731.1243494-1-maximmi@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Avoid using "goto" jump instruction unconditionally when we
can return directly. Remove unnecessary jump instructions in
do_tls_setsockopt_conf().
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
We replace proto_ops whenever TLS is configured for RX. But our
replacement also overrides sendpage_locked, which will crash
unless TX is also configured. Similarly we plug both of those
in for TLS_HW (NIC crypto offload) even tho TLS_HW has a completely
different implementation for TX.
Last but not least we always plug in something based on inet_stream_ops
even though a few of the callbacks differ for IPv6 (getname, release,
bind).
Use a callback building method similar to what we do for struct proto.
Fixes: c46234ebb4 ("tls: RX path for ktls")
Fixes: d4ffb02dee ("net/tls: enable sk_msg redirect to tls socket egress")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The proto ops ->stream_memory_read() is currently only used
by TCP to check whether psock queue is empty or not. We need
to rename it before reusing it for non-TCP protocols, and
adjust the exsiting users accordingly.
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211008203306.37525-2-xiyou.wangcong@gmail.com
AES_CCM_128 and CHACHA20_POLY1305 are already supported by tls,
similar to setsockopt, getsockopt also needs to support these
two algorithms.
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The RFC8998 specification defines the use of the ShangMi algorithm
cipher suites in TLS 1.3, and also supports the GCM/CCM mode using
the SM4 algorithm.
Signed-off-by: Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
When a netdev with active TLS offload goes down, tls_device_down is
called to stop the offload and tear down the TLS context. However, the
socket stays alive, and it still points to the TLS context, which is now
deallocated. If a netdev goes up, while the connection is still active,
and the data flow resumes after a number of TCP retransmissions, it will
lead to a use-after-free of the TLS context.
This commit addresses this bug by keeping the context alive until its
normal destruction, and implements the necessary fallbacks, so that the
connection can resume in software (non-offloaded) kTLS mode.
On the TX side tls_sw_fallback is used to encrypt all packets. The RX
side already has all the necessary fallbacks, because receiving
non-decrypted packets is supported. The thing needed on the RX side is
to block resync requests, which are normally produced after receiving
non-decrypted packets.
The necessary synchronization is implemented for a graceful teardown:
first the fallbacks are deployed, then the driver resources are released
(it used to be possible to have a tls_dev_resync after tls_dev_del).
A new flag called TLS_RX_DEV_DEGRADED is added to indicate the fallback
mode. It's used to skip the RX resync logic completely, as it becomes
useless, and some objects may be released (for example, resync_async,
which is allocated and freed by the driver).
Fixes: e8f6979981 ("net/tls: Add generic NIC offload infrastructure")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Replace commas with semicolons. Commas introduce unnecessary
variability in the code structure and are hard to see. What is done
is essentially described by the following Coccinelle semantic patch
(http://coccinelle.lip6.fr/):
// <smpl>
@@ expression e1,e2; @@
e1
-,
+;
e2
... when any
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Link: https://lore.kernel.org/r/1602412498-32025-6-git-send-email-Julia.Lawall@inria.fr
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
