[RFC PATCH v3 1/4] resource: Request IO port regions from children of ioport_resource

[John Garry <john.garry@huawei.com>]

Currently request_region() requests an IO port region directly from the
top resource, ioport_resource.

There is an issue here, in that drivers may successfully request an IO
port region even if the IO port region has not even been mapped in
(in pci_remap_iospace()).

This may lead to crashes when the system has no PCI host, or, has a host
but it has failed enumeration, while drivers still attempt to access PCI
IO ports, as below:

root@(none)$root@(none)$ insmod f71882fg.ko
 Unable to handle kernel paging request at virtual address ffff7dfffee0002e
 Mem abort info:
   ESR = 0x96000046
   Exception class = DABT (current EL), IL = 32 bits
   SET = 0, FnV = 0
   EA = 0, S1PTW = 0
 Data abort info:
   ISV = 0, ISS = 0x00000046
   CM = 0, WnR = 1
 swapper pgtable: 4k pages, 48-bit VAs, pgdp = (____ptrval____)
 [ffff7dfffee0002e] pgd=000000000141c003, pud=000000000141d003, pmd=0000000000000000
 Internal error: Oops: 96000046 [#1] PREEMPT SMP
 Modules linked in: f71882fg(+)
 CPU: 8 PID: 2732 Comm: insmod Not tainted 5.1.0-rc1-00002-gab1a0e9200b8-dirty #102
 Hardware name: Huawei Taishan 2280 /D05, BIOS Hisilicon D05 IT21 Nemo 2.0 RC0 04/18/2018
 pstate: 80000005 (Nzcv daif -PAN -UAO)
 pc : logic_outb+0x54/0xb8
 lr : f71882fg_find+0x64/0x390 [f71882fg]
 sp : ffff000013393aa0
 x29: ffff000013393aa0 x28: ffff000008b98b10
 x27: ffff000013393df0 x26: 0000000000000100
 x25: ffff801f8c872d30 x24: ffff000011420000
 x23: ffff801fb49d2940 x22: ffff000011291000
 x21: 000000000000002e x20: 0000000000000087
 x19: ffff000013393b44 x18: ffffffffffffffff
 x17: 0000000000000000 x16: 0000000000000000
 x15: ffff00001127d6c8 x14: ffff801f8cfd691c
 x13: 0000000000000000 x12: 0000000000000000
 x11: 0000000000000003 x10: 0000801feace2000
 x9 : 0000000000000000 x8 : ffff841fa654f280
 x7 : 0000000000000000 x6 : 0000000000ffc0e3
 x5 : ffff000011291360 x4 : ffff801fb4949f00
 x3 : 0000000000ffbffe x2 : 76e767a63713d500
 x1 : ffff7dfffee0002e x0 : ffff7dfffee00000
 Process insmod (pid: 2732, stack limit = 0x(____ptrval____))
 Call trace:
  logic_outb+0x54/0xb8
  f71882fg_find+0x64/0x390 [f71882fg]
  f71882fg_init+0x38/0xc70 [f71882fg]
  do_one_initcall+0x5c/0x198
  do_init_module+0x54/0x1b0
  load_module+0x1dc4/0x2158
  __se_sys_init_module+0x14c/0x1e8
  __arm64_sys_init_module+0x18/0x20
  el0_svc_common+0x5c/0x100
  el0_svc_handler+0x2c/0x80
  el0_svc+0x8/0xc
 Code: d2bfdc00 f2cfbfe0 f2ffffe0 8b000021 (39000034)
 ---[ end trace fd4f35b610829a48 ]---
Segmentation fault
root@(none)$

Note that the f71882fg driver correctly calls request_muxed_region().

This issue was originally reported in [1].

This patch changes the functionality of request{muxed_}_region() to
request a region from a direct child descendent of the top
ioport_resource.

In this, if the IO port region has not been mapped for a particular IO
region, the PCI IO resource would also not have been inserted, and so a
suitable child region will not exist. As such,
request_{muxed_}region() calls will fail.

A side note: there are many drivers in the kernel which fail to even call
request_{muxed_}region() prior to IO port accesses, and they also need to
be fixed (to call request_{muxed_}region(), as appropriate) separately.

[1] https://lore.kernel.org/linux-pci/56F209A9.4040304@huawei.com

Signed-off-by: John Garry <john.garry@huawei.com>
---
 include/linux/ioport.h | 11 ++++++++---
 kernel/resource.c      | 28 ++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index da0ebaec25f0..76288b8783ff 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -217,15 +217,20 @@ static inline bool resource_contains(struct resource *r1, struct resource *r2)
 
 
 /* Convenience shorthand with allocation */
-#define request_region(start,n,name)		__request_region(&ioport_resource, (start), (n), (name), 0)
-#define request_muxed_region(start,n,name)	__request_region(&ioport_resource, (start), (n), (name), IORESOURCE_MUXED)
+#define request_region(start, n, name)		__request_region_from_children(&ioport_resource, (start), (n), (name), 0)
+#define request_muxed_region(start, n, name)	__request_region_from_children(&ioport_resource, (start), (n), (name), IORESOURCE_MUXED)
 #define __request_mem_region(start,n,name, excl) __request_region(&iomem_resource, (start), (n), (name), excl)
 #define request_mem_region(start,n,name) __request_region(&iomem_resource, (start), (n), (name), 0)
 #define request_mem_region_exclusive(start,n,name) \
 	__request_region(&iomem_resource, (start), (n), (name), IORESOURCE_EXCLUSIVE)
 #define rename_region(region, newname) do { (region)->name = (newname); } while (0)
 
-extern struct resource * __request_region(struct resource *,
+extern struct resource *__request_region(struct resource *,
+					resource_size_t start,
+					resource_size_t n,
+					const char *name, int flags);
+
+extern struct resource *__request_region_from_children(struct resource *,
 					resource_size_t start,
 					resource_size_t n,
 					const char *name, int flags);
diff --git a/kernel/resource.c b/kernel/resource.c
index 92190f62ebc5..87ed200eda8b 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1097,6 +1097,34 @@ resource_size_t resource_alignment(struct resource *res)
 
 static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);
 
+/**
+ * __request_region_from_children - create a new busy region from a child
+ * @parent: parent resource descriptor
+ * @start: resource start address
+ * @n: resource region size
+ * @name: reserving caller's ID string
+ * @flags: IO resource flags
+ */
+struct resource *__request_region_from_children(struct resource *parent,
+						resource_size_t start,
+						resource_size_t n,
+						const char *name, int flags)
+{
+	struct resource *res = __request_region(parent, start, n, name, flags);
+
+	if (res && res->parent == parent) {
+		/*
+		 * This is a direct descendent of the parent, which is
+		 * what we didn't want.
+		 */
+		__release_region(parent, start, n);
+		res = NULL;
+	}
+
+	return res;
+}
+EXPORT_SYMBOL(__request_region_from_children);
+
 /**
  * __request_region - create a new busy resource region
  * @parent: parent resource descriptor
-- 
2.17.1