net/smc: reset sndbuf_desc if freed

When an SMC connection is created, and there is a problem to
create an RMB or DMB, the previously created send buffer is
thrown away as well including buffer descriptor freeing.
Make sure the connection no longer references the freed
buffer descriptor, otherwise bugs like this are possible:

[71556.835148] =============================================================================
[71556.835168] BUG kmalloc-128 (Tainted: G    B      OE    ): Poison overwritten
[71556.835172] -----------------------------------------------------------------------------

[71556.835179] INFO: 0x00000000d20894be-0x00000000aaef63e9 @offset=2724. First byte 0x0 instead of 0x6b
[71556.835215] INFO: Allocated in __smc_buf_create+0x184/0x578 [smc] age=0 cpu=5 pid=46726
[71556.835234]     ___slab_alloc+0x5a4/0x690
[71556.835239]     __slab_alloc.constprop.0+0x70/0xb0
[71556.835243]     kmem_cache_alloc_trace+0x38e/0x3f8
[71556.835250]     __smc_buf_create+0x184/0x578 [smc]
[71556.835257]     smc_buf_create+0x2e/0xe8 [smc]
[71556.835264]     smc_listen_work+0x516/0x6a0 [smc]
[71556.835275]     process_one_work+0x280/0x478
[71556.835280]     worker_thread+0x66/0x368
[71556.835287]     kthread+0x17a/0x1a0
[71556.835294]     ret_from_fork+0x28/0x2c
[71556.835301] INFO: Freed in smc_buf_create+0xd8/0xe8 [smc] age=0 cpu=5 pid=46726
[71556.835307]     __slab_free+0x246/0x560
[71556.835311]     kfree+0x398/0x3f8
[71556.835318]     smc_buf_create+0xd8/0xe8 [smc]
[71556.835324]     smc_listen_work+0x516/0x6a0 [smc]
[71556.835328]     process_one_work+0x280/0x478
[71556.835332]     worker_thread+0x66/0x368
[71556.835337]     kthread+0x17a/0x1a0
[71556.835344]     ret_from_fork+0x28/0x2c
[71556.835348] INFO: Slab 0x00000000a0744551 objects=51 used=51 fp=0x0000000000000000 flags=0x1ffff00000010200
[71556.835352] INFO: Object 0x00000000563480a1 @offset=2688 fp=0x00000000289567b2

[71556.835359] Redzone 000000006783cde2: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb  ................
[71556.835363] Redzone 00000000e35b876e: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb  ................
[71556.835367] Redzone 0000000023074562: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb  ................
[71556.835372] Redzone 00000000b9564b8c: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb  ................
[71556.835376] Redzone 00000000810c6362: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb  ................
[71556.835380] Redzone 0000000065ef52c3: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb  ................
[71556.835384] Redzone 00000000c5dd6984: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb  ................
[71556.835388] Redzone 000000004c480f8f: bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb  ................
[71556.835392] Object 00000000563480a1: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
[71556.835397] Object 000000009c479d06: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
[71556.835401] Object 000000006e1dce92: 6b 6b 6b 6b 00 00 00 00 6b 6b 6b 6b 6b 6b 6b 6b  kkkk....kkkkkkkk
[71556.835405] Object 00000000227f7cf8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
[71556.835410] Object 000000009a701215: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
[71556.835414] Object 000000003731ce76: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
[71556.835418] Object 00000000f7085967: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
[71556.835422] Object 0000000007f99927: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5  kkkkkkkkkkkkkkk.
[71556.835427] Redzone 00000000579c4913: bb bb bb bb bb bb bb bb                          ........
[71556.835431] Padding 00000000305aef82: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a  ZZZZZZZZZZZZZZZZ
[71556.835435] Padding 00000000b1cdd722: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a  ZZZZZZZZZZZZZZZZ
[71556.835438] Padding 00000000c7568199: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a  ZZZZZZZZZZZZZZZZ
[71556.835442] Padding 00000000fad4c4d4: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a  ZZZZZZZZZZZZZZZZ
[71556.835451] CPU: 0 PID: 47939 Comm: kworker/0:15 Tainted: G    B      OE     5.9.0-rc1uschi+ #54
[71556.835456] Hardware name: IBM 3906 M03 703 (LPAR)
[71556.835464] Workqueue: events smc_listen_work [smc]
[71556.835470] Call Trace:
[71556.835478]  [<00000000d5eaeb10>] show_stack+0x90/0xf8
[71556.835493]  [<00000000d66fc0f8>] dump_stack+0xa8/0xe8
[71556.835499]  [<00000000d61a511c>] check_bytes_and_report+0x104/0x130
[71556.835504]  [<00000000d61a57b2>] check_object+0x26a/0x2e0
[71556.835509]  [<00000000d61a59bc>] alloc_debug_processing+0x194/0x238
[71556.835514]  [<00000000d61a8c14>] ___slab_alloc+0x5a4/0x690
[71556.835519]  [<00000000d61a9170>] __slab_alloc.constprop.0+0x70/0xb0
[71556.835524]  [<00000000d61aaf66>] kmem_cache_alloc_trace+0x38e/0x3f8
[71556.835530]  [<000003ff80549bbc>] __smc_buf_create+0x184/0x578 [smc]
[71556.835538]  [<000003ff8054a396>] smc_buf_create+0x2e/0xe8 [smc]
[71556.835545]  [<000003ff80540c16>] smc_listen_work+0x516/0x6a0 [smc]
[71556.835549]  [<00000000d5f0f448>] process_one_work+0x280/0x478
[71556.835554]  [<00000000d5f0f6a6>] worker_thread+0x66/0x368
[71556.835559]  [<00000000d5f18692>] kthread+0x17a/0x1a0
[71556.835563]  [<00000000d6abf3b8>] ret_from_fork+0x28/0x2c
[71556.835569] INFO: lockdep is turned off.
[71556.835573] FIX kmalloc-128: Restoring 0x00000000d20894be-0x00000000aaef63e9=0x6b

[71556.835577] FIX kmalloc-128: Marking all objects used

Fixes: fd7f3a7 ("net/smc: remove freed buffer from list")
Reviewed-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/smc_core.c

@@ -1779,6 +1779,7 @@ int smc_buf_create(struct smc_sock *smc, bool is_smcd)
 		list_del(&smc->conn.sndbuf_desc->list);
 		mutex_unlock(&smc->conn.lgr->sndbufs_lock);
 		smc_buf_free(smc->conn.lgr, false, smc->conn.sndbuf_desc);
+		smc->conn.sndbuf_desc = NULL;
 	}
 	return rc;
 }