linux-stable.git/net/smc, branch master

net/smc: reject CHID-0 ACCEPT that matches an empty ism_dev slot

2026-05-14T10:20:06+00:00

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 
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Xiang Mei 
Link: https://patch.msgid.link/20260511062138.2839584-1-xmei5@asu.edu
Signed-off-by: Paolo Abeni

net/smc: avoid NULL deref of conn->lnk in smc_msg_event tracepoint

2026-05-13T01:44:36+00:00

The smc_msg_event tracepoint class, shared by smc_tx_sendmsg and
smc_rx_recvmsg, unconditionally dereferences smc->conn.lnk:

	__string(name, smc->conn.lnk->ibname)

conn->lnk is only set for SMC-R; for SMC-D it is NULL. Other code on
these paths already handles this (e.g. !conn->lnk in
SMC_STAT_RMB_TX_SIZE_SMALL()). With the tracepoint enabled, the first
sendmsg()/recvmsg() on an SMC-D socket crashes:

  Oops: general protection fault, probably for non-canonical address
  KASAN: null-ptr-deref in range [...]
  RIP: 0010:strlen+0x1e/0xa0
  Call Trace:
   trace_event_raw_event_smc_msg_event (net/smc/smc_tracepoint.h:44)
   smc_rx_recvmsg (net/smc/smc_rx.c:515)
   smc_recvmsg (net/smc/af_smc.c:2859)
   __sys_recvfrom (net/socket.c:2315)
   __x64_sys_recvfrom (net/socket.c:2326)
   do_syscall_64

The faulting address 0x3e0 is offsetof(struct smc_link, ibname),
confirming the NULL ->lnk deref. Enabling the tracepoint requires
root, but the trigger itself is unprivileged: socket(AF_SMC, ...) has
no capability check, and SMC-D negotiation needs no admin step on
s390 or on x86 with the loopback ISM device loaded.

Log an empty device name for SMC-D instead of dereferencing NULL.

Fixes: aff3083f10bf ("net/smc: Introduce tracepoints for tx and rx msg")
Reported-by: Weiming Shi 
Signed-off-by: Xiang Mei 
Reviewed-by: Dust Li 
Reviewed-by: Sidraya Jayagond 
Signed-off-by: Jakub Kicinski

net/smc: fix sleep-inside-lock in __smc_setsockopt() causing local DoS

2026-05-13T01:43:40+00:00

A logic flaw in __smc_setsockopt() allows a local unprivileged user to
cause a Denial of Service (DoS) by holding the socket lock indefinitely.

The function __smc_setsockopt() calls copy_from_sockptr() while holding
lock_sock(sk). By passing a userfaultfd-monitored memory page (or
FUSE-backed memory on systems where unprivileged userfaultfd is disabled)
as the optval, an attacker can halt execution during the copy operation,
keeping the lock held.

Combined with asynchronous tear-down operations like shutdown(), this
exhausts the kernel wq (kworkers) and triggers the hung task watchdog.

[  240.123456] INFO: task kworker/u8:2 blocked for more than 120 seconds.
[  240.123489] Call Trace:
[  240.123501]  smc_shutdown+...
[  240.123512]  lock_sock_nested+...

This patch moves the user-space copy outside the lock_sock() critical
section to prevent the issue.

Fixes: a6a6fe27bab4 ("net/smc: Dynamic control handshake limitation by socket options")
Signed-off-by: Nicolò Coccia 
Reviewed-by: Dust Li 
Tested-by: Dust Li 
Signed-off-by: Jakub Kicinski

net/smc: fix missing sk_err when TCP handshake fails

2026-05-07T15:36:34+00:00

In smc_connect_work(), when the underlying TCP handshake fails, the error
code (rc) must be propagated to sk_err to ensure userspace can correctly
retrieve the error status via SO_ERROR. Currently, the code only handles
a restricted set of error codes (e.g., EPIPE, ECONNREFUSED). If other
errors occurs, such as EHOSTUNREACH, sk_err remains unset (zero).

This affects applications that rely on SO_ERROR to determine connect
outcome. For example, higher versions of Go's netpoller treats
SO_ERROR == 0 combined with a failed getpeername() as a spurious wakeup
and re-enters epoll_wait(). Under ET mode, no further edge will be
generated since the socket is already in a terminal state, causing the
connect to hang indefinitely or until a user-specified timeout, if one
is set.

Fixes: 50717a37db03 ("net/smc: nonblocking connect rework")
Signed-off-by: D. Wythe 
Reviewed-by: Dust Li 
Link: https://patch.msgid.link/20260506014105.27093-1-alibuda@linux.alibaba.com
Signed-off-by: Jakub Kicinski

net/smc: avoid early lgr access in smc_clc_wait_msg

2026-04-23T18:00:57+00:00

A CLC decline can be received while the handshake is still in an early
stage, before the connection has been associated with a link group.

The decline handling in smc_clc_wait_msg() updates link-group level sync
state for first-contact declines, but that state only exists after link
group setup has completed. Guard the link-group update accordingly and
keep the per-socket peer diagnosis handling unchanged.

This preserves the existing sync_err handling for established link-group
contexts and avoids touching link-group state before it is available.

Fixes: 0cfdd8f92cac ("smc: connection and link group creation")
Cc: stable@kernel.org
Reported-by: Yuan Tan 
Reported-by: Yifan Wu 
Reported-by: Juefei Pu 
Reported-by: Xin Liu 
Signed-off-by: Ruijie Li 
Signed-off-by: Ren Wei 
Reviewed-by: Dust Li 
Link: https://patch.msgid.link/08c68a5c817acf198cce63d22517e232e8d60718.1776850759.git.ruijieli51@gmail.com
Signed-off-by: Jakub Kicinski

net/smc: fix double-free of smc_spd_priv when tee() duplicates splice pipe buffer

2026-03-21T01:59:30+00:00

smc_rx_splice() allocates one smc_spd_priv per pipe_buffer and stores
the pointer in pipe_buffer.private.  The pipe_buf_operations for these
buffers used .get = generic_pipe_buf_get, which only increments the page
reference count when tee(2) duplicates a pipe buffer.  The smc_spd_priv
pointer itself was not handled, so after tee() both the original and the
cloned pipe_buffer share the same smc_spd_priv *.

When both pipes are subsequently released, smc_rx_pipe_buf_release() is
called twice against the same object:

  1st call: kfree(priv)  sock_put(sk)  smc_rx_update_cons()  [correct]
  2nd call: kfree(priv)  sock_put(sk)  smc_rx_update_cons()  [UAF]

KASAN reports a slab-use-after-free in smc_rx_pipe_buf_release(), which
then escalates to a NULL-pointer dereference and kernel panic via
smc_rx_update_consumer() when it chases the freed priv->smc pointer:

  BUG: KASAN: slab-use-after-free in smc_rx_pipe_buf_release+0x78/0x2a0
  Read of size 8 at addr ffff888004a45740 by task smc_splice_tee_/74
  Call Trace:
   
   dump_stack_lvl+0x53/0x70
   print_report+0xce/0x650
   kasan_report+0xc6/0x100
   smc_rx_pipe_buf_release+0x78/0x2a0
   free_pipe_info+0xd4/0x130
   pipe_release+0x142/0x160
   __fput+0x1c6/0x490
   __x64_sys_close+0x4f/0x90
   do_syscall_64+0xa6/0x1a0
   entry_SYSCALL_64_after_hwframe+0x77/0x7f
   

  BUG: kernel NULL pointer dereference, address: 0000000000000020
  RIP: 0010:smc_rx_update_consumer+0x8d/0x350
  Call Trace:
   
   smc_rx_pipe_buf_release+0x121/0x2a0
   free_pipe_info+0xd4/0x130
   pipe_release+0x142/0x160
   __fput+0x1c6/0x490
   __x64_sys_close+0x4f/0x90
   do_syscall_64+0xa6/0x1a0
   entry_SYSCALL_64_after_hwframe+0x77/0x7f
   
  Kernel panic - not syncing: Fatal exception

Beyond the memory-safety problem, duplicating an SMC splice buffer is
semantically questionable: smc_rx_update_cons() would advance the
consumer cursor twice for the same data, corrupting receive-window
accounting.  A refcount on smc_spd_priv could fix the double-free, but
the cursor-accounting issue would still need to be addressed separately.

The .get callback is invoked by both tee(2) and splice_pipe_to_pipe()
for partial transfers; both will now return -EFAULT.  Users who need
to duplicate SMC socket data must use a copy-based read path.

Fixes: 9014db202cb7 ("smc: add support for splice()")
Signed-off-by: Qi Tang 
Link: https://patch.msgid.link/20260318064847.23341-1-tpluszz77@gmail.com
Signed-off-by: Jakub Kicinski

net/smc: fix NULL dereference and UAF in smc_tcp_syn_recv_sock()

2026-03-17T02:31:28+00:00

Syzkaller reported a panic in smc_tcp_syn_recv_sock() [1].

smc_tcp_syn_recv_sock() is called in the TCP receive path
(softirq) via icsk_af_ops->syn_recv_sock on the clcsock (TCP
listening socket). It reads sk_user_data to get the smc_sock
pointer. However, when the SMC listen socket is being closed
concurrently, smc_close_active() sets clcsock->sk_user_data
to NULL under sk_callback_lock, and then the smc_sock itself
can be freed via sock_put() in smc_release().

This leads to two issues:

1) NULL pointer dereference: sk_user_data is NULL when
   accessed.
2) Use-after-free: sk_user_data is read as non-NULL, but the
   smc_sock is freed before its fields (e.g., queued_smc_hs,
   ori_af_ops) are accessed.

The race window looks like this (the syzkaller crash [1]
triggers via the SYN cookie path: tcp_get_cookie_sock() ->
smc_tcp_syn_recv_sock(), but the normal tcp_check_req() path
has the same race):

  CPU A (softirq)              CPU B (process ctx)

  tcp_v4_rcv()
    TCP_NEW_SYN_RECV:
    sk = req->rsk_listener
    sock_hold(sk)
    /* No lock on listener */
                               smc_close_active():
                                 write_lock_bh(cb_lock)
                                 sk_user_data = NULL
                                 write_unlock_bh(cb_lock)
                                 ...
                                 smc_clcsock_release()
                                 sock_put(smc->sk) x2
                                   -> smc_sock freed!
    tcp_check_req()
      smc_tcp_syn_recv_sock():
        smc = user_data(sk)
          -> NULL or dangling
        smc->queued_smc_hs
          -> crash!

Note that the clcsock and smc_sock are two independent objects
with separate refcounts. TCP stack holds a reference on the
clcsock, which keeps it alive, but this does NOT prevent the
smc_sock from being freed.

Fix this by using RCU and refcount_inc_not_zero() to safely
access smc_sock. Since smc_tcp_syn_recv_sock() is called in
the TCP three-way handshake path, taking read_lock_bh on
sk_callback_lock is too heavy and would not survive a SYN
flood attack. Using rcu_read_lock() is much more lightweight.

- Set SOCK_RCU_FREE on the SMC listen socket so that
  smc_sock freeing is deferred until after the RCU grace
  period. This guarantees the memory is still valid when
  accessed inside rcu_read_lock().
- Use rcu_read_lock() to protect reading sk_user_data.
- Use refcount_inc_not_zero(&smc->sk.sk_refcnt) to pin the
  smc_sock. If the refcount has already reached zero (close
  path completed), it returns false and we bail out safely.

Note: smc_hs_congested() has a similar lockless read of
sk_user_data without rcu_read_lock(), but it only checks for
NULL and accesses the global smc_hs_wq, never dereferencing
any smc_sock field, so it is not affected.

Reproducer was verified with mdelay injection and smc_run,
the issue no longer occurs with this patch applied.

[1] https://syzkaller.appspot.com/bug?extid=827ae2bfb3a3529333e9

Fixes: 8270d9c21041 ("net/smc: Limit backlog connections")
Reported-by: syzbot+827ae2bfb3a3529333e9@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/67eaf9b8.050a0220.3c3d88.004a.GAE@google.com/T/
Suggested-by: Eric Dumazet 
Reviewed-by: Eric Dumazet 
Signed-off-by: Jiayuan Chen 
Link: https://patch.msgid.link/20260312092909.48325-1-jiayuan.chen@linux.dev
Signed-off-by: Jakub Kicinski

Merge tag 'net-7.0-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2026-02-26T16:00:13+00:00

Pull networking fixes from Paolo Abeni:
 "Including fixes from IPsec, Bluetooth and netfilter

  Current release - regressions:

   - wifi: fix dev_alloc_name() return value check

   - rds: fix recursive lock in rds_tcp_conn_slots_available

  Current release - new code bugs:

   - vsock: lock down child_ns_mode as write-once

  Previous releases - regressions:

   - core:
      - do not pass flow_id to set_rps_cpu()
      - consume xmit errors of GSO frames

   - netconsole: avoid OOB reads, msg is not nul-terminated

   - netfilter: h323: fix OOB read in decode_choice()

   - tcp: re-enable acceptance of FIN packets when RWIN is 0

   - udplite: fix null-ptr-deref in __udp_enqueue_schedule_skb().

   - wifi: brcmfmac: fix potential kernel oops when probe fails

   - phy: register phy led_triggers during probe to avoid AB-BA deadlock

   - eth:
      - bnxt_en: fix deleting of Ntuple filters
      - wan: farsync: fix use-after-free bugs caused by unfinished tasklets
      - xscale: check for PTP support properly

  Previous releases - always broken:

   - tcp: fix potential race in tcp_v6_syn_recv_sock()

   - kcm: fix zero-frag skb in frag_list on partial sendmsg error

   - xfrm:
      - fix race condition in espintcp_close()
      - always flush state and policy upon NETDEV_UNREGISTER event

   - bluetooth:
      - purge error queues in socket destructors
      - fix response to L2CAP_ECRED_CONN_REQ

   - eth:
      - mlx5:
         - fix circular locking dependency in dump
         - fix "scheduling while atomic" in IPsec MAC address query
      - gve: fix incorrect buffer cleanup for QPL
      - team: avoid NETDEV_CHANGEMTU event when unregistering slave
      - usb: validate USB endpoints"

* tag 'net-7.0-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (72 commits)
  netfilter: nf_conntrack_h323: fix OOB read in decode_choice()
  dpaa2-switch: validate num_ifs to prevent out-of-bounds write
  net: consume xmit errors of GSO frames
  vsock: document write-once behavior of the child_ns_mode sysctl
  vsock: lock down child_ns_mode as write-once
  selftests/vsock: change tests to respect write-once child ns mode
  net/mlx5e: Fix "scheduling while atomic" in IPsec MAC address query
  net/mlx5: Fix missing devlink lock in SRIOV enable error path
  net/mlx5: E-switch, Clear legacy flag when moving to switchdev
  net/mlx5: LAG, disable MPESW in lag_disable_change()
  net/mlx5: DR, Fix circular locking dependency in dump
  selftests: team: Add a reference count leak test
  team: avoid NETDEV_CHANGEMTU event when unregistering slave
  net: mana: Fix double destroy_workqueue on service rescan PCI path
  MAINTAINERS: Update maintainer entry for QUALCOMM ETHQOS ETHERNET DRIVER
  dpll: zl3073x: Remove redundant cleanup in devm_dpll_init()
  selftests/net: packetdrill: Verify acceptance of FIN packets when RWIN is 0
  tcp: re-enable acceptance of FIN packets when RWIN is 0
  vsock: Use container_of() to get net namespace in sysctl handlers
  net: usb: kaweth: validate USB endpoints
  ...

Convert remaining multi-line kmalloc_obj/flex GFP_KERNEL uses

2026-02-22T16:26:33+00:00

Conversion performed via this Coccinelle script:

  // SPDX-License-Identifier: GPL-2.0-only
  // Options: --include-headers-for-types --all-includes --include-headers --keep-comments
  virtual patch

  @gfp depends on patch && !(file in "tools") && !(file in "samples")@
  identifier ALLOC = {kmalloc_obj,kmalloc_objs,kmalloc_flex,
 		    kzalloc_obj,kzalloc_objs,kzalloc_flex,
		    kvmalloc_obj,kvmalloc_objs,kvmalloc_flex,
		    kvzalloc_obj,kvzalloc_objs,kvzalloc_flex};
  @@

  	ALLOC(...
  -		, GFP_KERNEL
  	)

  $ make coccicheck MODE=patch COCCI=gfp.cocci

Build and boot tested x86_64 with Fedora 42's GCC and Clang:

Linux version 6.19.0+ (user@host) (gcc (GCC) 15.2.1 20260123 (Red Hat 15.2.1-7), GNU ld version 2.44-12.fc42) #1 SMP PREEMPT_DYNAMIC 1970-01-01
Linux version 6.19.0+ (user@host) (clang version 20.1.8 (Fedora 20.1.8-4.fc42), LLD 20.1.8) #1 SMP PREEMPT_DYNAMIC 1970-01-01

Signed-off-by: Kees Cook 
Signed-off-by: Linus Torvalds

Convert more 'alloc_obj' cases to default GFP_KERNEL arguments

2026-02-22T04:03:00+00:00

This converts some of the visually simpler cases that have been split
over multiple lines.  I only did the ones that are easy to verify the
resulting diff by having just that final GFP_KERNEL argument on the next
line.

Somebody should probably do a proper coccinelle script for this, but for
me the trivial script actually resulted in an assertion failure in the
middle of the script.  I probably had made it a bit _too_ trivial.

So after fighting that far a while I decided to just do some of the
syntactically simpler cases with variations of the previous 'sed'
scripts.

The more syntactically complex multi-line cases would mostly really want
whitespace cleanup anyway.

Signed-off-by: Linus Torvalds