linux.git/net/smc, branch v7.2 Linux kernel source tree net/smc: fix TOCTOU race between smc_listen_out() and listener close 2026-08-06T11:35:41+00:00 Sidraya Jayagond sidraya@linux.ibm.com 2026-08-03T07:07:01+00:00 185a4caeecabc150106deda1da170b09f2ad803f smc_listen_out() reads lsmc->sk.sk_state without the listener lock, then acquires lock_sock_nested() only after the check passes. This opens a window where smc_close_active() can transition the listener to SMC_CLOSED, call smc_close_cleanup_listen() to drain the accept queue, and release the lock, all between the lockless read and the delayed lock acquisition: smc_listen_work (smc_hs_wq) smc_close_active() ------------------------------- ------------------------- release_sock(child) if (sk_state == SMC_LISTEN) TRUE lock_sock(listener) sk_state = SMC_CLOSED smc_close_cleanup_listen() release_sock(listener) flush_work(tcp_listen_work) lock_sock_nested(listener) smc_accept_enqueue(listener, child) /* child enqueued on dead listener */ smc_close_active() flushes only tcp_listen_work. Work items already dispatched onto smc_hs_wq for the CLC handshake continue running unguarded. smc_accept_enqueue() takes a sock_hold() on the child that is never released, so the child smc_sock, its clcsock, and the reference all leak. A remote peer that opens TCP connections while the server calls close() can exhaust kernel memory. Move lock_sock_nested() to before the sk_state check so that the test and the enqueue are atomic under the listener lock. Fixes: fd57770dd198 ("net/smc: wait for pending work before clcsock release_sock") Reviewed-by: Mahanta Jambigi <mjambigi@linux.ibm.com> Signed-off-by: Sidraya Jayagond <sidraya@linux.ibm.com> Reviewed-by: Breno Leitao <leitao@debian.org> Reviewed-by: Dust Li <dust.li@linux.alibaba.com> Link: https://patch.msgid.link/20260803070701.126339-1-sidraya@linux.ibm.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
smc_listen_out() reads lsmc->sk.sk_state without the listener lock,
then acquires lock_sock_nested() only after the check passes. This
opens a window where smc_close_active() can transition the listener
to SMC_CLOSED, call smc_close_cleanup_listen() to drain the accept
queue, and release the lock, all between the lockless read and the
delayed lock acquisition:

  smc_listen_work (smc_hs_wq)          smc_close_active()
  -------------------------------      -------------------------
  release_sock(child)
  if (sk_state == SMC_LISTEN) TRUE
                                        lock_sock(listener)
                                        sk_state = SMC_CLOSED
                                        smc_close_cleanup_listen()
                                        release_sock(listener)
                                        flush_work(tcp_listen_work)
  lock_sock_nested(listener)
  smc_accept_enqueue(listener, child) /* child enqueued on dead listener */

smc_close_active() flushes only tcp_listen_work. Work items already
dispatched onto smc_hs_wq for the CLC handshake continue running
unguarded. smc_accept_enqueue() takes a sock_hold() on the child that
is never released, so the child smc_sock, its clcsock, and the
reference all leak. A remote peer that opens TCP connections while the
server calls close() can exhaust kernel memory.

Move lock_sock_nested() to before the sk_state check so that the test
and the enqueue are atomic under the listener lock.

Fixes: fd57770dd198 ("net/smc: wait for pending work before clcsock release_sock")
Reviewed-by: Mahanta Jambigi <mjambigi@linux.ibm.com>
Signed-off-by: Sidraya Jayagond <sidraya@linux.ibm.com>
Reviewed-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
Link: https://patch.msgid.link/20260803070701.126339-1-sidraya@linux.ibm.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
net: smc: fix splice entry lifetime imbalance in smc_rx_splice 2026-08-04T01:27:51+00:00 Daming Li d4n.for.sec@gmail.com 2026-07-30T14:55:52+00:00 5d9686af2976741bbd79b150d1c9e60b81e7f12e smc_rx_splice() passes pages to splice_to_pipe() before taking the references that cover the lifetime of each splice entry. In the VM-backed RMB path, splice_to_pipe() may drop unqueued entries through smc_rx_spd_release(), while queued entries are released later via the pipe buffer callback. The old post-splice accounting also derives the number of queued VM pages from an offset mutated while building the descriptor, and a multi-page splice pairs one sock_hold() with multiple sock_put() calls. Take the page and socket references for every candidate entry before splice_to_pipe(), and drop the matching private state, page reference, and socket reference from smc_rx_spd_release() for entries that never get queued. This fixes a refcount imbalance that can underflow page refcounts and trigger a use-after-free. Fixes: 9014db202cb7 ("smc: add support for splice()") Cc: stable@vger.kernel.org Reported-by: Vega <vega@nebusec.ai> Co-developed-by: Xiao Liu <lx24@stu.ynu.edu.cn> Signed-off-by: Xiao Liu <lx24@stu.ynu.edu.cn> Signed-off-by: Daming Li <d4n.for.sec@gmail.com> Signed-off-by: Ren Wei <enjou1224z@gmail.com> Reviewed-by: Dust Li <dust.li@linux.alibaba.com> Reviewed-by: Sidraya Jayagond <sidraya@linux.ibm.com> Link: https://patch.msgid.link/20260730145552.360287-2-enjou1224z@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
smc_rx_splice() passes pages to splice_to_pipe() before taking the
references that cover the lifetime of each splice entry. In the
VM-backed RMB path, splice_to_pipe() may drop unqueued entries through
smc_rx_spd_release(), while queued entries are released later via the
pipe buffer callback.

The old post-splice accounting also derives the number of queued VM pages
from an offset mutated while building the descriptor, and a multi-page
splice pairs one sock_hold() with multiple sock_put() calls.

Take the page and socket references for every candidate entry before
splice_to_pipe(), and drop the matching private state, page reference,
and socket reference from smc_rx_spd_release() for entries that never
get queued. This fixes a refcount imbalance that can underflow page
refcounts and trigger a use-after-free.

Fixes: 9014db202cb7 ("smc: add support for splice()")
Cc: stable@vger.kernel.org
Reported-by: Vega <vega@nebusec.ai>
Co-developed-by: Xiao Liu <lx24@stu.ynu.edu.cn>
Signed-off-by: Xiao Liu <lx24@stu.ynu.edu.cn>
Signed-off-by: Daming Li <d4n.for.sec@gmail.com>
Signed-off-by: Ren Wei <enjou1224z@gmail.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
Reviewed-by: Sidraya Jayagond <sidraya@linux.ibm.com>
Link: https://patch.msgid.link/20260730145552.360287-2-enjou1224z@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net/smc: fix qentry overwrite for CONFIRM_LINK and ADD_LINK_CONT in smc_llc_event_handler() 2026-07-31T23:29:17+00:00 Mahanta Jambigi mjambigi@linux.ibm.com 2026-07-29T13:01:53+00:00 976245094925bab9bc39366b2e9ab44ffcde61d0 The SMC_LLC_CONFIRM_LINK / SMC_LLC_ADD_LINK_CONT branch in smc_llc_event_handler() stores an incoming qentry into the local LLC flow without first checking whether a qentry is already pending. If a malicious or buggy peer sends a second CONFIRM_LINK or ADD_LINK_CONT request while a flow is active and flow->qentry is already set, smc_llc_flow_qentry_set() overwrites the pointer without freeing the previous allocation, leaking one kmalloc-96 object per spurious message. The sibling SMC_LLC_DELETE_LINK branch already has the correct !flow->qentry guard. Apply the same guard to the CONFIRM_LINK/ADD_LINK_CONT branch so that a duplicate message when qentry is already occupied falls through to break and is freed by the kfree(qentry) at the out: label, rather than silently leaking the existing allocation. The response direction (smc_llc_rx_response()) is unaffected: it already guards with flow->qentry at the equivalent site and drops duplicate responses correctly. Fixes: 0fb0b02bd6fd ("net/smc: adapt SMC client code to use the LLC flow") Signed-off-by: Mahanta Jambigi <mjambigi@linux.ibm.com> Reviewed-by: Hidayath Khan <hidayath@linux.ibm.com> Reviewed-by: Sidraya Jayagond <sidraya@linux.ibm.com> Reviewed-by: Dust Li <dust.li@linux.alibaba.com> Link: https://patch.msgid.link/20260729130153.970800-1-mjambigi@linux.ibm.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
The SMC_LLC_CONFIRM_LINK / SMC_LLC_ADD_LINK_CONT branch in
smc_llc_event_handler() stores an incoming qentry into the local LLC flow
without first checking whether a qentry is already pending. If a malicious or
buggy peer sends a second CONFIRM_LINK or ADD_LINK_CONT request while a flow is
active and flow->qentry is already set, smc_llc_flow_qentry_set() overwrites the
pointer without freeing the previous allocation, leaking one kmalloc-96 object
per spurious message.

The sibling SMC_LLC_DELETE_LINK branch already has the correct !flow->qentry
guard. Apply the same guard to the CONFIRM_LINK/ADD_LINK_CONT branch so that a
duplicate message when qentry is already occupied falls through to break and is
freed by the kfree(qentry) at the out: label, rather than silently leaking the
existing allocation.

The response direction (smc_llc_rx_response()) is unaffected: it already guards
with flow->qentry at the equivalent site and drops duplicate responses
correctly.

Fixes: 0fb0b02bd6fd ("net/smc: adapt SMC client code to use the LLC flow")
Signed-off-by: Mahanta Jambigi <mjambigi@linux.ibm.com>
Reviewed-by: Hidayath Khan <hidayath@linux.ibm.com>
Reviewed-by: Sidraya Jayagond <sidraya@linux.ibm.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
Link: https://patch.msgid.link/20260729130153.970800-1-mjambigi@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net/smc: fix socket use-after-free during link group termination 2026-07-28T09:22:43+00:00 Xuanqiang Luo luoxuanqiang@kylinos.cn 2026-07-23T10:54:54+00:00 f621d6ebeebb6374342571e4ddf45fdbc420f6cd __smc_lgr_terminate() drops conns_lock after finding a connection in lgr->conns_all, but before taking a reference on its socket. The connection is embedded in the socket, and its registration reference protects it only while the connection remains in the tree. A concurrent close can unregister the connection and drop that reference, freeing the socket before the termination worker reaches sock_hold(). The race is reachable when close overlaps link group termination. Local stress testing reproduced the use-after-free and KASAN reported: BUG: KASAN: slab-use-after-free in __smc_lgr_terminate.part.0 [smc] Write of size 4 by task kworker/3:3 Workqueue: events smc_lgr_terminate_work [smc] __smc_lgr_terminate.part.0 [smc] The socket was allocated by smc_create(), freed through slab_free_after_rcu_debug(), and was followed by: refcount_t: addition on 0; use-after-free. __smc_lgr_terminate.part.0 [smc] Take the socket reference while conns_lock still protects the tree entry. The unregister path then cannot drop the last reference until termination has finished using the socket. Fixes: 69318b5215f2 ("net/smc: improve abnormal termination locking") Cc: stable@vger.kernel.org Signed-off-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn> Reviewed-by: Mahanta Jambigi <mjambigi@linux.ibm.com> Link: https://patch.msgid.link/20260723105454.87016-1-xuanqiang.luo@linux.dev Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
__smc_lgr_terminate() drops conns_lock after finding a connection in
lgr->conns_all, but before taking a reference on its socket. The connection
is embedded in the socket, and its registration reference protects it only
while the connection remains in the tree.

A concurrent close can unregister the connection and drop that reference,
freeing the socket before the termination worker reaches sock_hold().

The race is reachable when close overlaps link group termination.
Local stress testing reproduced the use-after-free and KASAN reported:

  BUG: KASAN: slab-use-after-free in __smc_lgr_terminate.part.0 [smc]
  Write of size 4 by task kworker/3:3
  Workqueue: events smc_lgr_terminate_work [smc]
  __smc_lgr_terminate.part.0 [smc]

The socket was allocated by smc_create(), freed through
slab_free_after_rcu_debug(), and was followed by:

  refcount_t: addition on 0; use-after-free.
  __smc_lgr_terminate.part.0 [smc]

Take the socket reference while conns_lock still protects the tree entry.
The unregister path then cannot drop the last reference until termination
has finished using the socket.

Fixes: 69318b5215f2 ("net/smc: improve abnormal termination locking")
Cc: stable@vger.kernel.org
Signed-off-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
Reviewed-by: Mahanta Jambigi <mjambigi@linux.ibm.com>
Link: https://patch.msgid.link/20260723105454.87016-1-xuanqiang.luo@linux.dev
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket 2026-07-06T10:58:12+00:00 Xiang Mei xmei5@asu.edu 2026-06-30T18:32:27+00:00 9d160b35cc34a2ba8229d07651468a7848325135 smc_cdc_rx_handler() looks up the connection by token under the link group's conns_lock, drops the lock, and then dereferences conn and the smc_sock derived from it, ending in sock_hold(&smc->sk) inside smc_cdc_msg_recv(). No reference is held across the lock release. The only reference pinning the socket while the connection is discoverable in the link group is taken in smc_lgr_register_conn() (sock_hold) and dropped in __smc_lgr_unregister_conn() (sock_put), both under conns_lock. Once the handler drops conns_lock, a concurrent close() -> smc_release() -> smc_conn_free() -> smc_lgr_unregister_conn() can drop that reference and free the smc_sock, so the handler's later sock_hold() runs on freed memory: WARNING: lib/refcount.c:25 at refcount_warn_saturate Workqueue: rxe_wq do_work refcount_warn_saturate (lib/refcount.c:25) smc_cdc_msg_recv (net/smc/smc_cdc.c:430) smc_cdc_rx_handler (net/smc/smc_cdc.c:502) smc_wr_rx_tasklet_fn (net/smc/smc_wr.c:445) tasklet_action_common (kernel/softirq.c:938) handle_softirqs (kernel/softirq.c:622) Kernel panic - not syncing: panic_on_warn set Only SMC-R is affected. The SMC-D receive tasklet is stopped by tasklet_kill(&conn->rx_tsklet) in smc_conn_free() before the connection is unregistered, so it cannot run concurrently with the free. Take the socket reference while still holding conns_lock, so the registration reference can no longer be the last one, and drop it once the handler is done. Fixes: d7b0e37c1ac1 ("net/smc: restructure CDC message reception") Reported-by: Weiming Shi <bestswngs@gmail.com> Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Xiang Mei <xmei5@asu.edu> Link: https://patch.msgid.link/20260630183227.2044998-1-xmei5@asu.edu Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
smc_cdc_rx_handler() looks up the connection by token under the link
group's conns_lock, drops the lock, and then dereferences conn and the
smc_sock derived from it, ending in sock_hold(&smc->sk) inside
smc_cdc_msg_recv(). No reference is held across the lock release.

The only reference pinning the socket while the connection is
discoverable in the link group is taken in smc_lgr_register_conn()
(sock_hold) and dropped in __smc_lgr_unregister_conn() (sock_put), both
under conns_lock. Once the handler drops conns_lock, a concurrent
close() -> smc_release() -> smc_conn_free() -> smc_lgr_unregister_conn()
can drop that reference and free the smc_sock, so the handler's later
sock_hold() runs on freed memory:

  WARNING: lib/refcount.c:25 at refcount_warn_saturate
  Workqueue: rxe_wq do_work
   refcount_warn_saturate (lib/refcount.c:25)
   smc_cdc_msg_recv (net/smc/smc_cdc.c:430)
   smc_cdc_rx_handler (net/smc/smc_cdc.c:502)
   smc_wr_rx_tasklet_fn (net/smc/smc_wr.c:445)
   tasklet_action_common (kernel/softirq.c:938)
   handle_softirqs (kernel/softirq.c:622)
  Kernel panic - not syncing: panic_on_warn set

Only SMC-R is affected. The SMC-D receive tasklet is stopped by
tasklet_kill(&conn->rx_tsklet) in smc_conn_free() before the connection
is unregistered, so it cannot run concurrently with the free.

Take the socket reference while still holding conns_lock, so the
registration reference can no longer be the last one, and drop it once
the handler is done.

Fixes: d7b0e37c1ac1 ("net/smc: restructure CDC message reception")
Reported-by: Weiming Shi <bestswngs@gmail.com>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Xiang Mei <xmei5@asu.edu>
Link: https://patch.msgid.link/20260630183227.2044998-1-xmei5@asu.edu
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2026-05-28T21:02:21+00:00 Jakub Kicinski kuba@kernel.org 2026-05-21T22:02:54+00:00 d44646fc9eeb423ad50f3043f11f66f491d908a7 Cross-merge networking fixes after downstream PR (net-7.1-rc6). Conflicts: drivers/net/phy/air_en8811h.c d895767c33781 ("net: phy: air_en8811h: add AN8811HB MCU assert/deassert support") dddfadd75197e ("net: phy: Add Airoha phy library for shared code") 5226bb6634cdf ("net: phy: air_phy_lib: Factorize BuckPBus register accessors") e08f0ea6daf2e ("net: phy: Rename Airoha common BuckPBus register accessors") net/sched/sch_netem.c a2f6ed7b4873 ("net/sched: netem: add per-impairment extended statistics") 9552b11e3eda ("net/sched: fix packet loop on netem when duplicate is on") Adjacent changes: drivers/dpll/zl3073x/core.c c1224569cef0 ("dpll: zl3073x: make frequency monitor a per-device attribute") 54e65df8cf18 ("dpll: zl3073x: report FFO as DPLL vs input reference offset") net/iucv/af_iucv.c 347fdd4df85f ("af_iucv: convert to getsockopt_iter") 3589d20a666c ("net/iucv: fix locking in .getsockopt") Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Cross-merge networking fixes after downstream PR (net-7.1-rc6).

Conflicts:

drivers/net/phy/air_en8811h.c
  d895767c33781 ("net: phy: air_en8811h: add AN8811HB MCU assert/deassert support")
  dddfadd75197e ("net: phy: Add Airoha phy library for shared code")
  5226bb6634cdf ("net: phy: air_phy_lib: Factorize BuckPBus register accessors")
  e08f0ea6daf2e ("net: phy: Rename Airoha common BuckPBus register accessors")

net/sched/sch_netem.c
  a2f6ed7b4873 ("net/sched: netem: add per-impairment extended statistics")
  9552b11e3eda ("net/sched: fix packet loop on netem when duplicate is on")

Adjacent changes:

drivers/dpll/zl3073x/core.c
  c1224569cef0 ("dpll: zl3073x: make frequency monitor a per-device attribute")
  54e65df8cf18 ("dpll: zl3073x: report FFO as DPLL vs input reference offset")

net/iucv/af_iucv.c
  347fdd4df85f ("af_iucv: convert to getsockopt_iter")
  3589d20a666c ("net/iucv: fix locking in .getsockopt")

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net/smc: Do not re-initialize smc hashtables 2026-05-23T00:38:02+00:00 Alexandra Winter wintera@linux.ibm.com 2026-05-21T14:56:39+00:00 9e4389b0038781f19f97895186ed941ff8ac1678 INIT_HLIST_HEAD(&smc_v*_hashinfo.ht) are called after smc_nl_init(), proto_register() and sock_register(). This can lead to smc_v*_hashinfo.ht being reset even though hash entries already exist and are being used, possibly resulting in a corrupted list. Remove unnecessary and dangerous re-initialisation of smc_v*_hashinfo.ht in smc_init(); it is implicitly initialised to zero anyhow. Add HLIST_HEAD_INIT to the definitions for clarity. Fixes: f16a7dd5cf27 ("smc: netlink interface for SMC sockets") Suggested-by: Halil Pasic <pasic@linux.ibm.com> Signed-off-by: Alexandra Winter <wintera@linux.ibm.com> Acked-by: Halil Pasic <pasic@linux.ibm.com> Reviewed-by: Mahanta Jambigi <mjambigi@linux.ibm.com> Link: https://patch.msgid.link/20260521145639.10317-1-wintera@linux.ibm.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
INIT_HLIST_HEAD(&smc_v*_hashinfo.ht) are called after smc_nl_init(),
proto_register() and sock_register(). This can lead to smc_v*_hashinfo.ht
being reset even though hash entries already exist and are being used,
possibly resulting in a corrupted list.

Remove unnecessary and dangerous re-initialisation of smc_v*_hashinfo.ht in
smc_init(); it is implicitly initialised to zero anyhow. Add
HLIST_HEAD_INIT to the definitions for clarity.

Fixes: f16a7dd5cf27 ("smc: netlink interface for SMC sockets")
Suggested-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Acked-by: Halil Pasic <pasic@linux.ibm.com>
Reviewed-by: Mahanta Jambigi <mjambigi@linux.ibm.com>
Link: https://patch.msgid.link/20260521145639.10317-1-wintera@linux.ibm.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
smc: Use flexible array for SMCD connections 2026-05-21T00:13:18+00:00 Rosen Penev rosenp@gmail.com 2026-05-19T00:52:06+00:00 5026c42d7f147fb6bc4e063abfa5b52bfd52ca35 Store the per-DMB connection pointers in the SMCD device allocation instead of allocating a separate connection array. This keeps the connection table tied to the SMCD device lifetime and simplifies the allocation and cleanup paths. Signed-off-by: Rosen Penev <rosenp@gmail.com> Reviewed-by: Sidraya Jayagond <sidraya@linux.ibm.com> Link: https://patch.msgid.link/20260519005206.628071-1-rosenp@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Store the per-DMB connection pointers in the SMCD device allocation
instead of allocating a separate connection array.

This keeps the connection table tied to the SMCD device lifetime and
simplifies the allocation and cleanup paths.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Reviewed-by: Sidraya Jayagond <sidraya@linux.ibm.com>
Link: https://patch.msgid.link/20260519005206.628071-1-rosenp@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2026-05-14T17:08:06+00:00 Jakub Kicinski kuba@kernel.org 2026-04-30T19:49:56+00:00 878492af7d503f4b093ea903173500be00e9cbe7 Cross-merge networking fixes after downstream PR (net-7.1-rc4). No conflicts, or adjacent changes. Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Cross-merge networking fixes after downstream PR (net-7.1-rc4).

No conflicts, or adjacent changes.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
net/smc: reject CHID-0 ACCEPT that matches an empty ism_dev slot 2026-05-14T10:20:06+00:00 Xiang Mei xmei5@asu.edu 2026-05-11T06:21:38+00:00 277740023def559a4a2ddc3e8e784ee37a0f16a9 On the SMC-D client, slot 0 of ini->ism_dev[]/ini->ism_chid[] is reserved for an SMC-Dv1 device. smc_find_ism_v2_device_clnt() populates V2 entries starting at index 1, so when no V1 device is selected slot 0 is left in its kzalloc()'ed state with ism_dev[0] == NULL and ism_chid[0] == 0. smc_v2_determine_accepted_chid() then matches the peer's CHID against the array starting from index 0 using the CHID alone. A malicious peer replying to a SMC-Dv2-only proposal with d1.chid == 0 matches the empty slot, ini->ism_selected becomes 0, and the subsequent ism_dev[0]->lgr_lock dereference in smc_conn_create() faults at offsetof(struct smcd_dev, lgr_lock) == 0x68: BUG: KASAN: null-ptr-deref in _raw_spin_lock_bh+0x79/0xe0 Write of size 4 at addr 0000000000000068 by task exploit/144 Call Trace: _raw_spin_lock_bh smc_conn_create (net/smc/smc_core.c:1997) __smc_connect (net/smc/af_smc.c:1447) smc_connect (net/smc/af_smc.c:1720) __sys_connect __x64_sys_connect do_syscall_64 Require ism_dev[i] to be non-NULL before accepting a CHID match. Fixes: a7c9c5f4af7f ("net/smc: CLC accept / confirm V2") Reported-by: Weiming Shi <bestswngs@gmail.com> Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Xiang Mei <xmei5@asu.edu> Link: https://patch.msgid.link/20260511062138.2839584-1-xmei5@asu.edu Signed-off-by: Paolo Abeni <pabeni@redhat.com> 
On the SMC-D client, slot 0 of ini->ism_dev[]/ini->ism_chid[] is
reserved for an SMC-Dv1 device. smc_find_ism_v2_device_clnt()
populates V2 entries starting at index 1, so when no V1 device is
selected slot 0 is left in its kzalloc()'ed state with ism_dev[0] ==
NULL and ism_chid[0] == 0.

smc_v2_determine_accepted_chid() then matches the peer's CHID against
the array starting from index 0 using the CHID alone. A malicious
peer replying to a SMC-Dv2-only proposal with d1.chid == 0 matches
the empty slot, ini->ism_selected becomes 0, and the subsequent
ism_dev[0]->lgr_lock dereference in smc_conn_create() faults at
offsetof(struct smcd_dev, lgr_lock) == 0x68:

  BUG: KASAN: null-ptr-deref in _raw_spin_lock_bh+0x79/0xe0
  Write of size 4 at addr 0000000000000068 by task exploit/144
  Call Trace:
   _raw_spin_lock_bh
   smc_conn_create (net/smc/smc_core.c:1997)
   __smc_connect (net/smc/af_smc.c:1447)
   smc_connect (net/smc/af_smc.c:1720)
   __sys_connect
   __x64_sys_connect
   do_syscall_64

Require ism_dev[i] to be non-NULL before accepting a CHID match.

Fixes: a7c9c5f4af7f ("net/smc: CLC accept / confirm V2")
Reported-by: Weiming Shi <bestswngs@gmail.com>
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Xiang Mei <xmei5@asu.edu>
Link: https://patch.msgid.link/20260511062138.2839584-1-xmei5@asu.edu
Signed-off-by: Paolo Abeni <pabeni@redhat.com>