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Subject[PATCH 3/11] ACPI: Fix acpi_os_read_memory() and acpi_os_write_memory()
Date
From: Rafael J. Wysocki <rjw@sisk.pl>

The functions acpi_os_read_memory() and acpi_os_write_memory() do
two wrong things. First, they shouldn't call rcu_read_unlock()
before the looked up address is actually used for I/O, because in
that case the mapping it belongs to may be removed before the I/O
is done. Second, they shouldn't use the physical address if
there's no mapping for it, because that may lead to problems (at
least for the "write" case it's like sending data to a random
physical address in the hope it's going to work).

Make the rcu_read_unlock() be called by these functions when the I/O
is complete and modify them to dump stack and return error code if
the requested physical address is not present in the ACPI iomaps.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
drivers/acpi/osl.c | 31 +++++++++++++------------------
1 file changed, 13 insertions(+), 18 deletions(-)
Index: linux-2.6/drivers/acpi/osl.c
===================================================================
--- linux-2.6.orig/drivers/acpi/osl.c
+++ linux-2.6/drivers/acpi/osl.c
@@ -638,17 +638,17 @@ acpi_os_read_memory(acpi_physical_addres
{
u32 dummy;
void __iomem *virt_addr;
- int size = width / 8, unmap = 0;
+
+ if (!value)
+ value = &dummy;

rcu_read_lock();
- virt_addr = acpi_map_vaddr_lookup(phys_addr, size);
- rcu_read_unlock();
+ virt_addr = acpi_map_vaddr_lookup(phys_addr, width / 8);
if (!virt_addr) {
- virt_addr = acpi_os_ioremap(phys_addr, size);
- unmap = 1;
+ rcu_read_unlock();
+ WARN(true, "Address not mapped: %llx\n", phys_addr);
+ return AE_BAD_ADDRESS;
}
- if (!value)
- value = &dummy;

switch (width) {
case 8:
@@ -663,9 +663,7 @@ acpi_os_read_memory(acpi_physical_addres
default:
BUG();
}
-
- if (unmap)
- iounmap(virt_addr);
+ rcu_read_unlock();

return AE_OK;
}
@@ -674,14 +672,13 @@ acpi_status
acpi_os_write_memory(acpi_physical_address phys_addr, u32 value, u32 width)
{
void __iomem *virt_addr;
- int size = width / 8, unmap = 0;

rcu_read_lock();
- virt_addr = acpi_map_vaddr_lookup(phys_addr, size);
- rcu_read_unlock();
+ virt_addr = acpi_map_vaddr_lookup(phys_addr, width / 8);
if (!virt_addr) {
- virt_addr = acpi_os_ioremap(phys_addr, size);
- unmap = 1;
+ rcu_read_unlock();
+ WARN(true, "Address not mapped: %llx\n", phys_addr);
+ return AE_BAD_ADDRESS;
}

switch (width) {
@@ -697,9 +694,7 @@ acpi_os_write_memory(acpi_physical_addre
default:
BUG();
}
-
- if (unmap)
- iounmap(virt_addr);
+ rcu_read_unlock();

return AE_OK;
}


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