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HID: magicmouse: prevent unbounded recursion in magicmouse_raw_event()

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magicmouse_raw_event() handles DOUBLE_REPORT_ID (0xf7) packets, which pack
two touch reports into one, by splitting the packet and calling itself on
each half. The only guard against runaway recursion is a "size < 1" check,
which stops zero-sized calls but does not bound the recursion depth.

A malicious HID device that matches this driver can send a report starting
with DOUBLE_REPORT_ID and filled with the sequence [0xf7, 0x00]. Each level
consumes two bytes and recurses on the remainder, so an incoming report of
up to HID_MAX_BUFFER_SIZE (16 KiB) drives roughly 8000 nested calls. That
easily exhausts the 16 KiB kernel stack, leading to a stack overflow: a
panic with CONFIG_VMAP_STACK, or memory corruption without it.

A double report only ever wraps two normal reports; it is never
legitimately nested. Refuse to re-enter the DOUBLE_REPORT_ID case from a
recursive call so the recursion depth is bounded to two, while all valid
packets keep being parsed exactly as before.

Fixes: a462230e16 ("HID: magicmouse: enable Magic Trackpad support")
Link: https://lore.kernel.org/linux-input/20260706181347.700DB1F00A3F@smtp.kernel.org/
Cc: stable@vger.kernel.org
Signed-off-by: Jose Villaseñor Montfort <pepemontfort@gmail.com>
Reviewed-by: Alec Hall <signshop.alec@gmail.com>
Tested-by: Alec Hall <signshop.alec@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
This commit is contained in:
Jose Villaseñor Montfort 2026-07-14 23:35:26 -06:00 committed by Jiri Kosina
parent 28a3e326fa
commit db8d634128
1 changed files with 20 additions and 5 deletions
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25
drivers/hid/hid-magicmouse.c
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@ -383,8 +383,8 @@ static void magicmouse_emit_touch(struct magicmouse_sc *msc, int raw_id, u8 *tda
}
}
static int magicmouse_raw_event(struct hid_device *hdev,
struct hid_report *report, u8 *data, int size)
static int __magicmouse_raw_event(struct hid_device *hdev,
struct hid_report *report, u8 *data, int size, bool nested)
{
struct magicmouse_sc *msc = hid_get_drvdata(hdev);
struct input_dev *input = msc->input;
@ -495,6 +495,15 @@ static int magicmouse_raw_event(struct hid_device *hdev,
* packet.
*/
/*
* A double report only ever wraps two normal reports, so it is
* never nested. Refuse to recurse a second time; otherwise a
* malicious device could chain DOUBLE_REPORT_ID packets to drive
* unbounded recursion and overflow the kernel stack.
*/
if (nested)
return 0;
/* Ensure that we have at least 2 elements (report type and size) */
if (size < 2)
return 0;
@ -506,9 +515,9 @@ static int magicmouse_raw_event(struct hid_device *hdev,
return 0;
}
magicmouse_raw_event(hdev, report, data + 2, data[1]);
magicmouse_raw_event(hdev, report, data + 2 + data[1],
size - 2 - data[1]);
__magicmouse_raw_event(hdev, report, data + 2, data[1], true);
__magicmouse_raw_event(hdev, report, data + 2 + data[1],
size - 2 - data[1], true);
return 0;
default:
return 0;
@ -534,6 +543,12 @@ static int magicmouse_raw_event(struct hid_device *hdev,
return 1;
}
static int magicmouse_raw_event(struct hid_device *hdev,
struct hid_report *report, u8 *data, int size)
{
return __magicmouse_raw_event(hdev, report, data, size, false);
}
static int magicmouse_event(struct hid_device *hdev, struct hid_field *field,
struct hid_usage *usage, __s32 value)
{