Re: [PATCH net v2 0/2] kcm: don't sleep in softirq when the lower socket uses kTLS

[Jiayuan Chen <jiayuan.chen@linux.dev>]

On 10/16/26 10:44 AM, Rishikesh Jethwani wrote:
> When a TCP socket with software kTLS RX is attached to a KCM mux,


Can we just reject such combo ?


> psock_data_ready() calls strp_data_ready() from softirq, which calls the
> socket's read_sock(). For kTLS that is tls_sw_read_sock(), which can
> sleep, and CONFIG_DEBUG_ATOMIC_SLEEP reports it on every run of a
> loopback reproducer.
>
> Patch 1 is the fix: KCM parses inline only when read_sock is
> tcp_read_sock() and otherwise defers to the strparser work, which runs
> under lock_sock(). It applies and builds on its own, including on
> stable kernels.
>
> Patch 2 addresses review feedback on v1 and is needed by patch 1.
> kstrp, the workqueue that deferred work runs on, is an ordered
> workqueue shared by every strparser user (KCM, sockmap, espintcp,
> ovpn). With patch 1 alone, a KCM psock decrypting kTLS records in
> software on kstrp would delay parsing and message timeouts for every
> other strparser socket on the system. Patch 2 makes kstrp per-CPU. It
> has no Fixes tag: the ordered workqueue is as old as strparser, and it
> only becomes a real problem for KCM over kTLS with patch 1.
>
> Other strparser users are not affected by the bug fixed in patch 1:
> espintcp is itself a TCP ULP and cannot be combined with kTLS, ovpn
> installs its own ops built from inet_stream_ops, and sockmap reads
> through tcp_bpf_strp_read_sock() and is mutually exclusive with kTLS
> RX (do_tls_setsockopt_conf() rejects sockets with a psock).
>
> Testing: with patch 1, 5/5 runs of the reproducer produce no splat and
> full datagram delivery; without it every run hits "BUG: sleeping
> function called from invalid context" in strp_data_ready ->
> tls_sw_read_sock. Multi-record messages (>16 KiB each) also deliver
> completely with kTLS RX installed before the KCM attach and the whole
> stream queued before the reader starts. With patch 2, test_sockmap and the ovpn TCP selftests
> pass, strparser work runs concurrently across sockets, and dmesg shows
> no warnings.
>
> v2:
>   - add patch 2 (kstrp per-CPU), per review
>   - read sock->ops with READ_ONCE(), pairing with update_sk_prot()
>
> v1: https://lore.kernel.org/netdev/20261013033920.2069285-1-rjethwani@purestorage.com/
>
> Rishikesh Jethwani (2):
>    kcm: defer receive parsing when the lower socket's read_sock may sleep
>    strparser: don't serialize all parser work on one ordered workqueue
>
>   net/kcm/kcmsock.c         | 33 +++++++++++++++++++++++++++++++--
>   net/strparser/strparser.c |  2 +-
>   2 files changed, 32 insertions(+), 3 deletions(-)
>