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Subject[STABLE PATCH .26 .27] ACPI: avoid empty file name in sysfs
From: Peter Gruber <nokos@gmx.net>

upstream 4feba70a2c1a1a0c96909f657f48b2e11e682370

Since commit bc45b1d39a925b56796bebf8a397a0491489d85c acpi tables are
allowed to have an empty signature and /sys/firmware/acpi/tables uses the
signature as filename. Applications using naive recursion through /sys
loop forever. A possible solution would be: (replacing the zero length
filename with the string "NULL")

http://bugzilla.kernel.org/show_bug.cgi?id=11539

Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>
---
drivers/acpi/system.c | 25 +++++++++++++++++--------
1 files changed, 17 insertions(+), 8 deletions(-)
diff --git a/drivers/acpi/system.c b/drivers/acpi/system.c
index 1d74171..62ec75e 100644
--- a/drivers/acpi/system.c
+++ b/drivers/acpi/system.c
@@ -78,9 +78,15 @@ static ssize_t acpi_table_show(struct kobject *kobj,
container_of(bin_attr, struct acpi_table_attr, attr);
struct acpi_table_header *table_header = NULL;
acpi_status status;
+ char name[ACPI_NAME_SIZE];
+
+ if (strncmp(table_attr->name, "NULL", 4))
+ memcpy(name, table_attr->name, ACPI_NAME_SIZE);
+ else
+ memcpy(name, "\0\0\0\0", 4);

status =
- acpi_get_table(table_attr->name, table_attr->instance,
+ acpi_get_table(name, table_attr->instance,
&table_header);
if (ACPI_FAILURE(status))
return -ENODEV;
@@ -95,21 +101,24 @@ static void acpi_table_attr_init(struct acpi_table_attr *table_attr,
struct acpi_table_header *header = NULL;
struct acpi_table_attr *attr = NULL;

- memcpy(table_attr->name, table_header->signature, ACPI_NAME_SIZE);
+ if (table_header->signature[0] != '\0')
+ memcpy(table_attr->name, table_header->signature,
+ ACPI_NAME_SIZE);
+ else
+ memcpy(table_attr->name, "NULL", 4);

list_for_each_entry(attr, &acpi_table_attr_list, node) {
- if (!memcmp(table_header->signature, attr->name,
- ACPI_NAME_SIZE))
+ if (!memcmp(table_attr->name, attr->name, ACPI_NAME_SIZE))
if (table_attr->instance < attr->instance)
table_attr->instance = attr->instance;
}
table_attr->instance++;

if (table_attr->instance > 1 || (table_attr->instance == 1 &&
- !acpi_get_table(table_header->
- signature, 2,
- &header)))
- sprintf(table_attr->name + 4, "%d", table_attr->instance);
+ !acpi_get_table
+ (table_header->signature, 2, &header)))
+ sprintf(table_attr->name + ACPI_NAME_SIZE, "%d",
+ table_attr->instance);

table_attr->attr.size = 0;
table_attr->attr.read = acpi_table_show;
--
1.6.0.4.617.g2baf


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