ice: fix memory corruption bug with suspend and rebuild

The ice driver would previously panic after suspend. This is caused
from the driver *only* calling the ice_vsi_free_q_vectors() function by
itself, when it is suspending. Since commit b3e7b3a6ee92 ("ice: prevent
NULL pointer deref during reload") the driver has zeroed out
num_q_vectors, and only restored it in ice_vsi_cfg_def().

This further causes the ice_rebuild() function to allocate a zero length
buffer, after which num_q_vectors is updated, and then the new value of
num_q_vectors is used to index into the zero length buffer, which
corrupts memory.

The fix entails making sure all the code referencing num_q_vectors only
does so after it has been reset via ice_vsi_cfg_def().

I didn't perform a full bisect, but I was able to test against 6.1.77
kernel and that ice driver works fine for suspend/resume with no panic,
so sometime since then, this problem was introduced.

Also clean up an un-needed init of a local variable in the function
being modified.

PANIC from 6.8.0-rc1:

[1026674.915596] PM: suspend exit
[1026675.664697] ice 0000:17:00.1: PTP reset successful
[1026675.664707] ice 0000:17:00.1: 2755 msecs passed between update to cached PHC time
[1026675.667660] ice 0000:b1:00.0: PTP reset successful
[1026675.675944] ice 0000:b1:00.0: 2832 msecs passed between update to cached PHC time
[1026677.137733] ixgbe 0000:31:00.0 ens787: NIC Link is Up 1 Gbps, Flow Control: None
[1026677.190201] BUG: kernel NULL pointer dereference, address: 0000000000000010
[1026677.192753] ice 0000:17:00.0: PTP reset successful
[1026677.192764] ice 0000:17:00.0: 4548 msecs passed between update to cached PHC time
[1026677.197928] #PF: supervisor read access in kernel mode
[1026677.197933] #PF: error_code(0x0000) - not-present page
[1026677.197937] PGD 1557a7067 P4D 0
[1026677.212133] ice 0000:b1:00.1: PTP reset successful
[1026677.212143] ice 0000:b1:00.1: 4344 msecs passed between update to cached PHC time
[1026677.212575]
[1026677.243142] Oops: 0000 [#1] PREEMPT SMP NOPTI
[1026677.247918] CPU: 23 PID: 42790 Comm: kworker/23:0 Kdump: loaded Tainted: G W 6.8.0-rc1+ #1
[1026677.257989] Hardware name: Intel Corporation M50CYP2SBSTD/M50CYP2SBSTD, BIOS SE5C620.86B.01.01.0005.2202160810 02/16/2022
[1026677.269367] Workqueue: ice ice_service_task [ice]
[1026677.274592] RIP: 0010:ice_vsi_rebuild_set_coalesce+0x130/0x1e0 [ice]
[1026677.281421] Code: 0f 84 3a ff ff ff 41 0f b7 74 ec 02 66 89 b0 22 02 00 00 81 e6 ff 1f 00 00 e8 ec fd ff ff e9 35 ff ff ff 48 8b 43 30 49 63 ed <41> 0f b7 34 24 41 83 c5 01 48 8b 3c e8 66 89 b7 aa 02 00 00 81 e6
[1026677.300877] RSP: 0018:ff3be62a6399bcc0 EFLAGS: 00010202
[1026677.306556] RAX: ff28691e28980828 RBX: ff28691e41099828 RCX: 0000000000188000
[1026677.314148] RDX: 0000000000000000 RSI: 0000000000000010 RDI: ff28691e41099828
[1026677.321730] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
[1026677.329311] R10: 0000000000000007 R11: ffffffffffffffc0 R12: 0000000000000010
[1026677.336896] R13: 0000000000000000 R14: 0000000000000000 R15: ff28691e0eaa81a0
[1026677.344472] FS: 0000000000000000(0000) GS:ff28693cbffc0000(0000) knlGS:0000000000000000
[1026677.353000] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[1026677.359195] CR2: 0000000000000010 CR3: 0000000128df4001 CR4: 0000000000771ef0
[1026677.366779] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[1026677.374369] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[1026677.381952] PKRU: 55555554
[1026677.385116] Call Trace:
[1026677.388023] <TASK>
[1026677.390589] ? __die+0x20/0x70
[1026677.394105] ? page_fault_oops+0x82/0x160
[1026677.398576] ? do_user_addr_fault+0x65/0x6a0
[1026677.403307] ? exc_page_fault+0x6a/0x150
[1026677.407694] ? asm_exc_page_fault+0x22/0x30
[1026677.412349] ? ice_vsi_rebuild_set_coalesce+0x130/0x1e0 [ice]
[1026677.418614] ice_vsi_rebuild+0x34b/0x3c0 [ice]
[1026677.423583] ice_vsi_rebuild_by_type+0x76/0x180 [ice]
[1026677.429147] ice_rebuild+0x18b/0x520 [ice]
[1026677.433746] ? delay_tsc+0x8f/0xc0
[1026677.437630] ice_do_reset+0xa3/0x190 [ice]
[1026677.442231] ice_service_task+0x26/0x440 [ice]
[1026677.447180] process_one_work+0x174/0x340
[1026677.451669] worker_thread+0x27e/0x390
[1026677.455890] ? __pfx_worker_thread+0x10/0x10
[1026677.460627] kthread+0xee/0x120
[1026677.464235] ? __pfx_kthread+0x10/0x10
[1026677.468445] ret_from_fork+0x2d/0x50
[1026677.472476] ? __pfx_kthread+0x10/0x10
[1026677.476671] ret_from_fork_asm+0x1b/0x30
[1026677.481050] </TASK>

Fixes: b3e7b3a6ee92 ("ice: prevent NULL pointer deref during reload")
Reported-by: Robert Elliott <[e-mail]>
Signed-off-by: Jesse Brandeburg <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Reviewed-by: Aleksandr Loktionov <[e-mail]>
Tested-by: Pucha Himasekhar Reddy <[e-mail]> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <[e-mail]>

drivers/net/ethernet/intel/ice/ice_lib.c

···
 {
 	struct ice_vsi_cfg_params params = {};
 	struct ice_coalesce_stored *coalesce;
-	int prev_num_q_vectors = 0;
+	int prev_num_q_vectors;
 	struct ice_pf *pf;
 	int ret;
 
···
 	if (WARN_ON(vsi->type == ICE_VSI_VF && !vsi->vf))
 		return -EINVAL;
 
-	coalesce = kcalloc(vsi->num_q_vectors,
-			   sizeof(struct ice_coalesce_stored), GFP_KERNEL);
-	if (!coalesce)
-		return -ENOMEM;
-
-	prev_num_q_vectors = ice_vsi_rebuild_get_coalesce(vsi, coalesce);
-
 	ret = ice_vsi_realloc_stat_arrays(vsi);
 	if (ret)
 		goto err_vsi_cfg;
···
 	ret = ice_vsi_cfg_def(vsi, &params);
 	if (ret)
 		goto err_vsi_cfg;
+
+	coalesce = kcalloc(vsi->num_q_vectors,
+			   sizeof(struct ice_coalesce_stored), GFP_KERNEL);
+	if (!coalesce)
+		return -ENOMEM;
+
+	prev_num_q_vectors = ice_vsi_rebuild_get_coalesce(vsi, coalesce);
 
 	ret = ice_vsi_cfg_tc_lan(pf, vsi);
 	if (ret) {
···
 
 err_vsi_cfg_tc_lan:
 	ice_vsi_decfg(vsi);
-err_vsi_cfg:
 	kfree(coalesce);
+err_vsi_cfg:
 	return ret;
 }