PCI: pci-epf-test: Fix free_mem in case of epc_set_bar failure

This fixes a double free bug exhibited by the pci_epf_test_set_bar function

in sequence from pci_epf_test_set_bar

        ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no,
                                 epf_bar);
           if (ret) {
                   pci_epf_free_space(epf, epf_test->reg[bar], bar,
                                      PRIMARY_INTERFACE);
                   dev_err(dev, "Failed to set BAR%d\n", bar);
                   if (bar == test_reg_bar)
                           return ret;
           }

pci_epf_test_core_init from two contexts: either in bind or from
init_notifier. epf_space should be freed only from bind in case
of error to avoid double free.

This can happens with the init_notifier that is called upon a perst
interrupt from the host (bind/unbind RC driver for instance).

to reproduce:
on the EP . start the epf-test driver
on the RC . unbind / rebind the pcie-stm32 driver 2 times

   22.877524] stm32-ep-pcie 48400000.pcie-ep: No free inbound window
[   22.883688] ------------[ cut here ]------------
[   22.888324] Trying to vfree() nonexistent vm area (00000000fe826670)
[   22.894685] WARNING: CPU: 0 PID: 94 at mm/vmalloc.c:2693 __vunmap+0x2d0/0x310
[   22.901741] Modules linked in: pci_epf_test crct10dif_ce irq_rpmsg
[   22.907892] CPU: 0 PID: 94 Comm: irq/56-perst_ir Not tainted 6.1.73 torvalds#36  [   22.914535] Hardware name: STMicroelectronics STM32MP257F VALID3 REVB/ MB1706 (DDR4 Power discrete) + MB1703 (DT)
[   22.924692] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[   22.931635] pc : __vunmap+0x2d0/0x310
[   22.935364] lr : __vunmap+0x2d0/0x310
[   22.938993] sp : ffff800009ed3b70
[   22.942314] x29: ffff800009ed3b70 x28: ffff0000066fac80 x27: ffff0000050bc000
[   22.949365] x26: 0000000000000000 x25: ffff800008f41968 x24: 0000000000000000
[   22.956515] x23: 0000000000000000 x22: ffff0000048cd010 x21: 0000000000000000
[   22.963664] x20: ffff80000a415000 x19: 0000000000000000 x18: ffff000004eb5d10
[   22.970714] x17: 0000000000000000 x16: 0000000000000000 x15: ffffffffffffffff
[   22.977864] x14: 0000000000000000 x13: 00000000000001bf x12: ffff000004eb5d10
[   22.985014] x11: 00000000ffffffea x10: ffff8000097da970 x9 : 0000000000000001
[   22.992064] x8 : 0000000000000001 x7 : 0000000000017fe8 x6 : c0000000ffffefff
[   22.999213] x5 : 0000000000057fa8 x4 : 0000000000000000 x3 : ffff800009ed3908
[   23.006363] x2 : ffff800009782868 x1 : 3776615508e77000 x0 : 0000000000000000
[   23.013413] Call trace:
[   23.015830]  __vunmap+0x2d0/0x310
[   23.019158]  vunmap+0x28/0x40
[   23.022083]  dma_direct_free+0xf8/0x120
[   23.025914]  dma_free_attrs+0x98/0xe0
[   23.029641]  pci_epf_free_space+0x48/0x80
[   23.033573]  pci_epf_test_core_init+0x1d0/0x1f0 [pci_epf_test]
[   23.039421]  pci_epf_test_notifier+0x18/0x90 [pci_epf_test]
[   23.044964]  atomic_notifier_call_chain+0x60/0x90
[   23.049599]  pci_epc_init_notify+0x28/0x40
[   23.053730]  dw_pcie_ep_init_notify+0x14/0x20
[   23.058061]  stm32_pcie_ep_perst_irq_thread+0x120/0x220
[   23.063297]  irq_thread_fn+0x2c/0xb0
[   23.066824]  irq_thread+0x174/0x260
[   23.070350]  kthread+0x110/0x120
[   23.073475]  ret_from_fork+0x10/0x20
[   23.077104] ---[ end trace 0000000000000000 ]---
[   23.081670] Unable to handle kernel paging request at virtual address fffffbfffe000000

Fixes: 349e7a8 ("PCI: endpoint: functions: Add an EP function to test PCI")
Change-Id: Id9d4137cf48c7ae101647e8b76e89978a34523d7
Signed-off-by: Christian Bruel <christian.bruel@foss.st.com>
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/linux-stm32/+/380530
Domain-Review: Fabrice GASNIER <fabrice.gasnier@foss.st.com>
Reviewed-by: Fabrice GASNIER <fabrice.gasnier@foss.st.com>
ACI: CITOOLS <MDG-smet-aci-reviews@list.st.com>
ACI: CIBUILD <MDG-smet-aci-builds@list.st.com>

Author: Christian Bruel

drivers/pci/endpoint/functions/pci-epf-test.c

@@ -735,8 +735,6 @@ static int pci_epf_test_set_bar(struct pci_epf *epf)
 		ret = pci_epc_set_bar(epc, epf->func_no, epf->vfunc_no,
 				      epf_bar);
 		if (ret) {
-			pci_epf_free_space(epf, epf_test->reg[bar], bar,
-					   PRIMARY_INTERFACE);
 			dev_err(dev, "Failed to set BAR%d\n", bar);
 			if (bar == test_reg_bar)
 				return ret;
@@ -877,6 +875,20 @@ static int pci_epf_test_alloc_space(struct pci_epf *epf)
 	return 0;
 }
 
+static void pci_epf_test_free_space(struct pci_epf *epf)
+{
+	struct pci_epf_test *epf_test = epf_get_drvdata(epf);
+	int bar;
+
+	for (bar = 0; bar < PCI_STD_NUM_BARS; bar++) {
+		if (epf_test->reg[bar]) {
+			pci_epf_free_space(epf, epf_test->reg[bar],
+					   bar, PRIMARY_INTERFACE);
+			epf_test->reg[bar] = NULL;
+		}
+	}
+}
+
 static void pci_epf_configure_bar(struct pci_epf *epf,
 				  const struct pci_epc_features *epc_features)
 {
@@ -931,8 +943,10 @@ static int pci_epf_test_bind(struct pci_epf *epf)
 
 	if (!core_init_notifier || force_core_init) {
 		ret = pci_epf_test_core_init(epf);
-		if (ret)
+		if (ret) {
+			pci_epf_test_free_space(epf);
 			return ret;
+		}
 	}
 
 	epf_test->dma_supported = true;