[RFC PATCH 1/2] resource: Request IO port regions from children of ioport_resource

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

Currently when we request an IO port region, the request is made directly
to the top resource, ioport_resource.

There is an issue here, in that drivers may 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 PCI host has not enumerated prior to
accessing the IO port region, as below:

root@(none)$ insmod f71805f.ko
[   32.264016] Unable to handle kernel paging request at virtual address ffff7dfffee0002e
[   32.279936] Mem abort info:
[   32.285536]   ESR = 0x96000046
[   32.291657]   Exception class = DABT (current EL), IL = 32 bits
[   32.303542]   SET = 0, FnV = 0
[   32.309661]   EA = 0, S1PTW = 0
[   32.315957] Data abort info:
[   32.321728]   ISV = 0, ISS = 0x00000046
[   32.329420]   CM = 0, WnR = 1
[   32.335367] swapper pgtable: 4k pages, 48-bit VAs, pgdp = (____ptrval____)
[   32.349174] [ffff7dfffee0002e] pgd=0000000001392003, pud=0000000001393003, pmd=0000000000000000
[   32.366652] Internal error: Oops: 96000046 [#1] PREEMPT SMP
[   32.377835] Modules linked in: f71805f(+)
[   32.385876] CPU: 4 PID: 2681 Comm: insmod Not tainted 5.0.0-00003-ga6247cc0f8f2 #52
[   32.401252] Hardware name: Huawei Taishan 2280 /D05, BIOS Hisilicon D05 IT21 Nemo 2.0 RC0 04/18/2018
[   32.419597] pstate: 80000005 (Nzcv daif -PAN -UAO)
[   32.429213] pc : logic_outb+0x54/0xb8
[   32.436556] lr : f71805f_find+0x2c/0x1b8 [f71805f]
[   32.446167] sp : ffff0000256bba90
[   32.452808] x29: ffff0000256bba90 x28: ffff000008b544d0
[   32.463468] x27: ffff0000256bbdf0 x26: 0000000000000100
[   32.474127] x25: 000000000000002c x24: ffff000011396000
[   32.484787] x23: ffff0000256bbb3e x22: ffff0000256bbb40
[   32.495446] x21: ffff000008b591b8 x20: 0000000000000087
[   32.506106] x19: 000000000000002e x18: ffffffffffffffff
[   32.516765] x17: 0000000000000000 x16: 0000000000000000
[   32.527424] x15: 0000000000000400 x14: 0000000000000400
[   32.538084] x13: 0000000000001832 x12: 0000000000000000
[   32.548743] x11: ffff801ffbf08ac0 x10: 0000801fead02000
[   32.559403] x9 : ffff801ffbffe840 x8 : 0000000000000001
[   32.570062] x7 : 0000000000210d00 x6 : 0000000000000000
[   32.580721] x5 : ffff801fb3eac380 x4 : ffff801ffbef4b20
[   32.591381] x3 : 0000000000ffbffe x2 : ffff0000256bbb40
[   32.602040] x1 : ffff7dfffee0002e x0 : ffff7dfffee00000
[   32.612701] Process insmod (pid: 2681, stack limit = 0x(____ptrval____))
[   32.626155] Call trace:
[   32.631050]  logic_outb+0x54/0xb8
[   32.637693]  f71805f_find+0x2c/0x1b8 [f71805f]
[   32.646607]  f71805f_init+0x38/0xe48 [f71805f]
[   32.655521]  do_one_initcall+0x5c/0x178
[   32.663212]  do_init_module+0x58/0x1b0
[   32.670728]  load_module+0x1dc8/0x2178
[   32.678243]  __se_sys_init_module+0x14c/0x1e8
[   32.686981]  __arm64_sys_init_module+0x18/0x20
[   32.695894]  el0_svc_common+0x60/0x100
[   32.703409]  el0_svc_handler+0x2c/0x80
[   32.710924]  el0_svc+0x8/0xc
[   32.716693] Code: d2bfdc00 f2cfbfe0 f2ffffe0 8b000021 (39000034)
[   32.728925] ---[ end trace ddb5e493ee686685 ]---
Segmentation fault
root@(none)$

This issue was originally reported in [1].

This patch changes the functionality of request_region() to request a
region of the direct children of the top ioport_resource.

In this, if the IO port region has not been mapped for a particular IO
region, a suitable child region will not exist, and, as such,
request_region() calls will fail.

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

[1] https://www.spinics.net/lists/linux-pci/msg49821.html

Signed-off-by: John Garry <john.garry@huawei.com>
---
 include/linux/ioport.h |  6 +++++-
 kernel/resource.c      | 19 +++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index da0ebaec25f0..cf40e1ed8211 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -217,7 +217,7 @@ 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_region(start,n,name)		__request_region_from_children(&ioport_resource, (start), (n), (name), 0)
 #define request_muxed_region(start,n,name)	__request_region(&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)
@@ -230,6 +230,10 @@ extern struct resource * __request_region(struct resource *,
 					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);
 /* Compatibility cruft */
 #define release_region(start,n)	__release_region(&ioport_resource, (start), (n))
 #define release_mem_region(start,n)	__release_region(&iomem_resource, (start), (n))
diff --git a/kernel/resource.c b/kernel/resource.c
index 915c02e8e5dd..4a4656bd6051 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1098,6 +1098,25 @@ resource_size_t resource_alignment(struct resource *res)
 
 static DECLARE_WAIT_QUEUE_HEAD(muxed_resource_wait);
 
+struct resource * __request_region_from_children(struct resource *parent,
+						 resource_size_t start,
+						 resource_size_t n,
+						 const char *name, int flags)
+{
+	struct resource *child;
+
+	/* TODO - add locking */
+	for (child = parent->child; child; child = child->sibling) {
+		struct resource *res = __request_region(child, start, n, name, flags);
+
+		if (res)
+			return res;
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL(__request_region_from_children);
+
 /**
  * __request_region - create a new busy resource region
  * @parent: parent resource descriptor
-- 
2.17.1