Re: [PATCH] RDMA/siw: Fix potential NULL pointer dereference in header processing

[Bernard Metzler <bernard.metzler@linux.dev>]

On 02.02.2026 11:06, Leon Romanovsky wrote:
> On Sun, Feb 01, 2026 at 06:23:37PM +0100, Bernard Metzler wrote:
>> On 31.01.2026 12:13, YunJe Shin wrote:
>>> If siw_get_hdr() returns -EINVAL before set_rx_fpdu_context(),
>>> qp->rx_fpdu can be NULL. Since the error path in siw_tcp_rx_data()
>>> dereferences qp->rx_fpdu->more_ddp_segs without checking, this
>>> may lead to a NULL pointer deref. Only check more_ddp_segs when
>>> rx_fpdu is present.
>>>
>>>
>>> [  101.384271] KASAN: null-ptr-deref in range
>>> [0x00000000000000c0-0x00000000000000c7]
>>> [  101.385071] CPU: 1 UID: 1000 PID: 265 Comm: exploit_poc Not tainted
>>> 6.19.0-rc7-g8dfce8991b95 #1 PREEMPT(voluntary)
>>> [  101.385418] Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX,
>>> 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
>>> [  101.385869] RIP: 0010:siw_tcp_rx_data+0x13ad/0x1e50
>>> [  101.386511] Code: 0b 89 34 24 e8 b4 49 1b fe 8b 34 24 48 8b ab f8
>>> 03 00 00 b8 ff ff 37 00 48 c1 e0 2a 48 8d bd c5 00 00 8
>>> [  101.386979] RSP: 0018:ffff88806d1083a0 EFLAGS: 00000207
>>> [  101.387243] RAX: dffffc0000000000 RBX: ffff88800d5ef000 RCX: 0000000000000000
>>> [  101.387545] RDX: 0000000000000018 RSI: 00000000ffffffea RDI: 00000000000000c5
>>> [  101.387829] RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000006
>>> [  101.388076] R10: ffff88800d5ef5be R11: 0000000000000001 R12: dffffc0000000000
>>> [  101.388316] R13: ffff88800d5ef3f4 R14: 0000000000000010 R15: ffff88800d5ef384
>>> [  101.388599] FS:  00000000110e2380(0000) GS:ffff8880e62af000(0000)
>>> knlGS:0000000000000000
>>> [  101.388819] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> [  101.389020] CR2: dffffc0000000018 CR3: 00000000092c7000 CR4: 00000000000006f0
>>> [  101.389324] Call Trace:
>>> [  101.389635]  <IRQ>
>>> [  101.389807]  ? lapic_next_event+0x10/0x20
>>> [  101.389978]  ? clockevents_program_event+0x1d0/0x280
>>> [  101.390121]  ? hrtimer_interrupt+0x319/0x7e0
>>> [  101.390269]  __tcp_read_sock+0x1ab/0x810
>>> [  101.390412]  ? __pfx_siw_tcp_rx_data+0x10/0x10
>>> [  101.390535]  ? __pfx___tcp_read_sock+0x10/0x10
>>> [  101.390658]  siw_qp_llp_data_ready+0x185/0x2c0
>>> [  101.390759]  ? __pfx_siw_qp_llp_data_ready+0x10/0x10
>>> [  101.390871]  ? tcp_event_data_recv+0x36a/0x7b0
>>> [  101.390967]  ? tcp_queue_rcv+0x30a/0x620
>>> [  101.391062]  tcp_data_queue+0x1ecc/0x4b40
>>> [  101.391164]  ? common_startup_64+0x13e/0x148
>>> [  101.391265]  ? __pfx_tcp_data_queue+0x10/0x10
>>> [  101.391358]  ? tcp_try_undo_loss+0x640/0x710
>>> [  101.391459]  ? __pfx_read_tsc+0x10/0x10
>>> [  101.391545]  ? ktime_get+0x60/0x140
>>> [  101.391669]  ? __pfx_do_sync_core+0x10/0x10
>>> [  101.391764]  tcp_rcv_established+0x801/0x35e0
>>> [  101.391864]  ? sk_filter_trim_cap+0x4ab/0xb20
>>> [  101.391963]  ? __pfx_tcp_inbound_hash+0x10/0x10
>>> [  101.392060]  ? __pfx_tcp_rcv_established+0x10/0x10
>>> [  101.392167]  ? bpf_skb_net_hdr_push+0x560/0x580
>>> [  101.392268]  ? _raw_spin_lock+0x7f/0xd0
>>> [  101.392363]  tcp_v4_do_rcv+0x525/0x8a0
>>> [  101.392461]  tcp_v4_rcv+0x249d/0x3e50
>>> [  101.392558]  ? kernel_text_address+0xa7/0x130
>>> [  101.392685]  ? __pfx_tcp_v4_rcv+0x10/0x10
>>> [  101.392779]  ? unwind_get_return_address+0x59/0xa0
>>> [  101.392897]  ? __pfx_raw_local_deliver+0x10/0x10
>>> [  101.393020]  ip_protocol_deliver_rcu+0x61/0x2e0
>>> [  101.393122]  ? __pfx_stack_trace_save+0x10/0x10
>>> [  101.393233]  ip_local_deliver_finish+0x332/0x4b0
>>> [  101.393333]  ? ip_finish_output2+0x71f/0x19a0
>>> [  101.393429]  ip_local_deliver+0x18f/0x2d0
>>> [  101.393530]  ? __pfx_ip_local_deliver+0x10/0x10
>>> [  101.393642]  ? __pfx___netif_receive_skb_core.constprop.0+0x10/0x10
>>> [  101.393789]  ? __kasan_mempool_poison_object+0xbb/0x190
>>> [  101.393899]  ? napi_skb_cache_put+0x23/0x190
>>> [  101.394001]  ? skb_defer_free_flush+0x145/0x1b0
>>> [  101.394100]  ? net_rx_action+0x349/0xfb0
>>> [  101.394215]  ? __asan_memset+0x23/0x50
>>> [  101.394315]  ? __tcp_push_pending_frames+0x8f/0x2f0
>>> [  101.394423]  ip_rcv+0x221/0x270
>>> [  101.394506]  ? __pfx_ip_rcv+0x10/0x10
>>> [  101.394627]  ? __pfx_ip_rcv+0x10/0x10
>>> [  101.394735]  __netif_receive_skb_one_core+0x161/0x1b0
>>> [  101.394876]  ? __pfx___netif_receive_skb_one_core+0x10/0x10
>>> [  101.395029]  ? _raw_spin_lock_irq+0x80/0xe0
>>> [  101.395154]  process_backlog+0x1e5/0x5e0
>>> [  101.395268]  ? napi_skb_cache_put+0x23/0x190
>>> [  101.395423]  __napi_poll+0x9a/0x500
>>> [  101.395533]  net_rx_action+0x988/0xfb0
>>> [  101.395671]  ? _raw_spin_lock_irq+0x80/0xe0
>>> [  101.395797]  ? __pfx_net_rx_action+0x10/0x10
>>> [  101.395948]  ? timerqueue_add+0x21b/0x320
>>> [  101.396093]  ? __hrtimer_run_queues+0x3de/0x790
>>> [  101.396251]  ? __pfx_read_tsc+0x10/0x10
>>> [  101.396365]  ? ktime_get+0x60/0x140
>>> [  101.396475]  handle_softirqs+0x18c/0x530
>>> [  101.396592]  ? __pfx_handle_softirqs+0x10/0x10
>>> [  101.396731]  do_softirq+0x3b/0x60
>>> [  101.396855]  </IRQ>
>>> [  101.396940]  <TASK>
>>> [  101.397004]  __local_bh_enable_ip+0x61/0x70
>>> [  101.397144]  __dev_queue_xmit+0x618/0x2fe0
>>> [  101.397257]  ? __local_bh_enable_ip+0x61/0x70
>>> [  101.397380]  ? __pfx___dev_queue_xmit+0x10/0x10
>>> [  101.397500]  ? sched_clock+0x10/0x30
>>> [  101.397613]  ? __pfx_selinux_ip_postroute_compat+0x10/0x10
>>> [  101.397770]  ? _raw_spin_trylock+0xaf/0x120
>>> [  101.397883]  ? selinux_ip_postroute+0x3e9/0x9d0
>>> [  101.398008]  ip_finish_output2+0x71f/0x19a0
>>> [  101.398125]  ? __pfx_ip_finish_output2+0x10/0x10
>>> [  101.398251]  ? __pfx_stack_trace_consume_entry+0x10/0x10
>>> [  101.398395]  __ip_finish_output.part.0+0x477/0x950
>>> [  101.398541]  ? __pfx___ip_finish_output.part.0+0x10/0x10
>>> [  101.398691]  ? nf_hook_slow+0xa7/0x1e0
>>> [  101.398796]  ip_output+0x260/0x4d0
>>> [  101.398903]  ? __pfx_ip_output+0x10/0x10
>>> [  101.399015]  ? __pfx_stack_trace_save+0x10/0x10
>>> [  101.399132]  ? __pfx_ip_finish_output+0x10/0x10
>>> [  101.399236]  ? kasan_save_stack+0x42/0x60
>>> [  101.399501]  ? ipv4_dst_check+0x10a/0x160
>>> [  101.399665]  __ip_queue_xmit+0xcfb/0x1d60
>>> [  101.399813]  ? __tcp_select_window+0xf8/0xed0
>>> [  101.399931]  ? __skb_clone+0x550/0x740
>>> [  101.400034]  __tcp_transmit_skb+0x29ce/0x3de0
>>> [  101.400159]  ? __pfx___tcp_transmit_skb+0x10/0x10
>>> [  101.400284]  ? kmem_cache_alloc_node_noprof+0x13b/0x4d0
>>> [  101.400423]  ? kasan_save_track+0x14/0x30
>>> [  101.400565]  tcp_write_xmit+0x11ba/0x7610
>>> [  101.400744]  ? skb_page_frag_refill+0x55/0x430
>>> [  101.400872]  __tcp_push_pending_frames+0x8f/0x2f0
>>> [  101.400999]  tcp_sendmsg_locked+0x156e/0x3b70
>>> [  101.401165]  ? __pfx_tcp_sendmsg_locked+0x10/0x10
>>> [  101.401362]  ? __pfx_selinux_socket_sendmsg+0x10/0x10
>>> [  101.401528]  ? _raw_spin_lock_bh+0x83/0xe0
>>> [  101.401733]  ? ldsem_up_read+0x12/0x40
>>> [  101.402061]  tcp_sendmsg+0x26/0x40
>>> [  101.402210]  __sys_sendto+0x364/0x430
>>> [  101.402346]  ? __pfx___sys_sendto+0x10/0x10
>>> [  101.402523]  ? ksys_write+0xf7/0x1c0
>>> [  101.402671]  ? __pfx_ksys_write+0x10/0x10
>>> [  101.402834]  __x64_sys_sendto+0xdb/0x1b0
>>> [  101.402968]  ? fpregs_assert_state_consistent+0x56/0xe0
>>> [  101.403107]  do_syscall_64+0xa4/0x320
>>> [  101.403254]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
>>> [  101.403554] RIP: 0033:0x42440d
>>> [  101.403982] Code: 02 48 c7 c0 ff ff ff ff eb b5 0f 1f 00 f3 0f 1e
>>> fa 80 3d 5d fc 08 00 00 41 89 ca 74 20 45 31 c9 45 31 9
>>> [  101.404392] RSP: 002b:00007ffc69a5f158 EFLAGS: 00000246 ORIG_RAX:
>>> 000000000000002c
>>> [  101.404659] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000042440d
>>> [  101.404864] RDX: 0000000000000030 RSI: 00007ffc69a5f180 RDI: 0000000000000003
>>> [  101.405069] RBP: 00007ffc69a5f200 R08: 0000000000000000 R09: 0000000000000000
>>> [  101.405257] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc69a5f318
>>> [  101.405416] R13: 00007ffc69a5f340 R14: 00000000004ae868 R15: 0000000000000001
>>> [  101.405634]  </TASK>
>>> [  101.405771] Modules linked in:
>>> [  101.406766] ---[ end trace 0000000000000000 ]---
>>> [  101.407214] RIP: 0010:siw_tcp_rx_data+0x13ad/0x1e50
>>> [  101.407387] Code: 0b 89 34 24 e8 b4 49 1b fe 8b 34 24 48 8b ab f8
>>> 03 00 00 b8 ff ff 37 00 48 c1 e0 2a 48 8d bd c5 00 00 8
>>> [  101.407946] RSP: 0018:ffff88806d1083a0 EFLAGS: 00000207
>>> [  101.408091] RAX: dffffc0000000000 RBX: ffff88800d5ef000 RCX: 0000000000000000
>>> [  101.408239] RDX: 0000000000000018 RSI: 00000000ffffffea RDI: 00000000000000c5
>>> [  101.408375] RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000006
>>> [  101.408508] R10: ffff88800d5ef5be R11: 0000000000000001 R12: dffffc0000000000
>>> [  101.408741] R13: ffff88800d5ef3f4 R14: 0000000000000010 R15: ffff88800d5ef384
>>> [  101.408897] FS:  00000000110e2380(0000) GS:ffff8880e62af000(0000)
>>> knlGS:0000000000000000
>>> [  101.409051] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> [  101.409181] CR2: dffffc0000000018 CR3: 00000000092c7000 CR4: 00000000000006f0
>>> [  101.409577] Kernel panic - not syncing: Fatal exception in interrupt
>>> [  101.410887] Kernel Offset: disabled
>>> [  101.411108] Rebooting in 1 seconds..
>>>
>>>
>>>
>>> Fixes: 8b6a361b8c48 ("rdma/siw: receive path")
>>> Signed-off-by: YunJe Shin <ioerts@kookmin.ac.kr>
>>> ---
>>>    drivers/infiniband/sw/siw/siw_qp_rx.c | 3 +--
>>>    1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/infiniband/sw/siw/siw_qp_rx.c b/drivers/infiniband/sw/siw/siw_qp_rx.c
>>> index e8a88b378d51..960f740cf46a 100644
>>> --- a/drivers/infiniband/sw/siw/siw_qp_rx.c
>>> +++ b/drivers/infiniband/sw/siw/siw_qp_rx.c
>>> @@ -1434,8 +1434,7 @@ int siw_tcp_rx_data(read_descriptor_t *rd_desc, struct sk_buff *skb,
>>>    			run_completion = 0;
>>>    		}
>>>    		if (unlikely(rv != 0 && rv != -EAGAIN)) {
>>> -			if ((srx->state > SIW_GET_HDR ||
>>
>> We cannot remove that state > SIW_GET_HDR condition.
>>
>> Consider this error case:
>> We received a header of say a short SEND comprising only
>> one DDP segment, and started data processing, while
>> encountering an error (too much data, no write permission
>> for the receive buffer, etc.). We have to complete the
>> current RECEIVE processing and surface a local completion,
>> since we already fetched the RQE from the receive queue.
> 
> Could you walk me through the code call chain?
> Don't we start with SIW_GET_HDR, which should initialize the qp->rx_fpdu
> pointer?
> 

Yes, we start with SIW_GET_HDR. If we got the complete header,
we move on to states for placing data and/or fetching trailer
CRC.

If we did not complete the header but encounter an error during
its parsing, such as an unsupported RDMA operation, we do not
leave SIW_GET_HDR state, but let the outer receive loop handle
the error case while in SIW_GET_HDR state. So far so good.

We did not consider the special error case that we are in
SIW_GET_HDR, but may have been unable to set the qp->rx_fpdu
receive context pointer, since it is a first fragment of a new
message and the header is malformed. In that case, we do not
assign a receive context and no local completion must be
generated.

If, at the other hand, it is the start of an expected consecutive
DDP fragment of a _fragmented_ message (checked via
'qp->rx_fpdu->more_ddp_segs'), we (1) already have a receive context
(was set during parsing the first correct DDP segment), and (2) we
shall complete that incomplete RDMA operation in error, since we
already started it when parsing the previous message fragment(s).

Yes that is all rather complicated ...

Thanks,
Bernard.




> Thanks
> 
>>
>>> -			     (qp->rx_fpdu && qp->rx_fpdu->more_ddp_segs)) &&
>>> +			if (qp->rx_fpdu && qp->rx_fpdu->more_ddp_segs &&
>>>    			    run_completion)
>>>    				siw_rdmap_complete(qp, rv);
>>