[patch 16/71] wmi: fix kernel panic when stack protection enabled.

From: Greg KH
Date: Fri Sep 04 2009 - 20:32:59 EST

2.6.30-stable review patch. If anyone has any objections, please let us know.

From: Costantino Leandro <lcostantino@xxxxxxxxx>

commit f3d83e2415445e5b157bef404d38674e9e8de169 upstream.

Kernel panic arise when stack protection is enabled, since strncat will
add a null terminating byte '\0'; So in functions
like this one (wmi_query_block):
char wc[4]="WC";
strncat(method, block->object_id, 2);
the length of wc should be n+1 (wc[5]) or stack protection
fault will arise. This is not noticeable when stack protection is
disabled,but , isn't good either.

Panic Trace
.... stack-protector: kernel stack corrupted in : fa7b182c
[<c04a6c40>] ? panic+0x45/0xd9
[<c012925d>] ? __stack_chk_fail+0x1c/0x40
[<fa7b182c>] ? wmi_query_block+0x15a/0x162 [wmi]
[<fa7b182c>] ? wmi_query_block+0x15a/0x162 [wmi]
[<fa7e7000>] ? acer_wmi_init+0x00/0x61a [acer_wmi]
[<fa7e7135>] ? acer_wmi_init+0x135/0x61a [acer_wmi]
[<c0101159>] ? do_one_initcall+0x50+0x126

Addresses http://bugzilla.kernel.org/show_bug.cgi?id=13514

Signed-off-by: Costantino Leandro <lcostantino@xxxxxxxxx>
Signed-off-by: Carlos Corbacho <carlos@xxxxxxxxxxxxxxxxxxx>
Cc: Len Brown <len.brown@xxxxxxxxx>
Cc: Bjorn Helgaas <bjorn.helgaas@xxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

drivers/platform/x86/wmi.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/platform/x86/wmi.c
+++ b/drivers/platform/x86/wmi.c
@@ -270,7 +270,7 @@ u32 method_id, const struct acpi_buffer
acpi_status status;
struct acpi_object_list input;
union acpi_object params[3];
- char method[4] = "WM";
+ char method[5] = "WM";

if (!find_guid(guid_string, &wblock))
return AE_ERROR;
@@ -328,8 +328,8 @@ struct acpi_buffer *out)
acpi_status status, wc_status = AE_ERROR;
struct acpi_object_list input, wc_input;
union acpi_object wc_params[1], wq_params[1];
- char method[4];
- char wc_method[4] = "WC";
+ char method[5];
+ char wc_method[5] = "WC";

if (!guid_string || !out)
@@ -410,7 +410,7 @@ const struct acpi_buffer *in)
acpi_handle handle;
struct acpi_object_list input;
union acpi_object params[2];
- char method[4] = "WS";
+ char method[5] = "WS";

if (!guid_string || !in)
return AE_BAD_DATA;

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