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HID: fix a potential bug in pointer casting

PATCH Applied Li Zefan 2 participants 2 messages Nov 14, 2007

Subsystems (2)
HID USB HID/hidbp drivers (USB keyboards, mice, remote controls, ...)
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Li Zefan

author
#0 lore raw

PATCH 1/1 HID: fix a potential bug in pointer casting

Don't directly cast list_head * to foo *, this works only when list is the first member of struct foo, and we should not make the assumption how members are ordered in the structure.

i.e. struct *f = (struct *f)pos will work if:

	struct foo {
		struct list_head list;
		int i;
	};

but will fail if:

	struct foo {
		int i;
		struct list_head list;
	}
Signed-off-by Li Zefan <[email protected]>
---
 drivers/hid/usbhid/hid-tmff.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
drivers/hid/usbhid/hid-tmff.c +4 -3
index 69882a7..144578b 100644
@@ -137,7 +137,8 @@ static int hid_tmff_play(struct input_dev *dev, void *data, struct ff_effect *ef
 int hid_tmff_init(struct hid_device *hid)
 {
 	struct tmff_device *tmff;
-	struct list_head *pos;
+	struct hid_report *report;
+	struct list_head *report_list;
 	struct hid_input *hidinput = list_entry(hid->inputs.next, struct hid_input, list);
 	struct input_dev *input_dev = hidinput->input;
 	const signed short *ff_bits = ff_joystick;

@@ -149,8 +150,8 @@ int hid_tmff_init(struct hid_device *hid)
 		return -ENOMEM;
 
 	/* Find the report to use */
-	list_for_each(pos, &hid->report_enum[HID_OUTPUT_REPORT].report_list) {
-		struct hid_report *report = (struct hid_report *)pos;
+	report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
+	list_for_each_entry(report, report_list, list) {
 		int fieldnum;
 
 		for (fieldnum = 0; fieldnum < report->maxfield; ++fieldnum) {
Signature · 1 line
1.5.3.rc7
Applied
#1 lore raw
Quoted 3 lines · Li Zefan

Don't directly cast list_head * to foo *, this works only when list is the first member of struct foo, and we should not make the assumption how members are ordered in the structure.

Hi,

applied to my tree, thanks!

Signature · 2 lines
Jiri Kosina
SUSE Labs