[Linux-kernel-mentees] [PATCH v1] usbhid: Fix slab-out-of-bounds write in hiddev_ioctl_usage()
Peilin Ye
yepeilin.cs at gmail.com
Sat Jul 18 23:12:18 UTC 2020
`uref->usage_index` is not always being properly checked, causing
hiddev_ioctl_usage() to go out of bounds under some cases. Fix it.
This patch fixes the following syzbot bug:
https://syzkaller.appspot.com/bug?id=f2aebe90b8c56806b050a20b36f51ed6acabe802
Reported-by: syzbot+34ee1b45d88571c2fa8b at syzkaller.appspotmail.com
Signed-off-by: Peilin Ye <yepeilin.cs at gmail.com>
---
This patch fixes the bug, but in an ugly way. Checks on `uref` are already
being done in this code:
if (cmd == HIDIOCGCOLLECTIONINDEX) {
if (uref->usage_index >= field->maxusage)
goto inval;
uref->usage_index =
array_index_nospec(uref->usage_index,
field->maxusage);
} else if (uref->usage_index >= field->report_count)
goto inval;
However it did not catch this bug since it's in an `else` bracket. Should
we move the above code out of the bracket? Would like to hear your opinion.
Thank you!
drivers/hid/usbhid/hiddev.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/hid/usbhid/hiddev.c b/drivers/hid/usbhid/hiddev.c
index 4140dea693e9..c63d07caacef 100644
--- a/drivers/hid/usbhid/hiddev.c
+++ b/drivers/hid/usbhid/hiddev.c
@@ -525,6 +525,8 @@ static noinline int hiddev_ioctl_usage(struct hiddev *hiddev, unsigned int cmd,
goto goodreturn;
case HIDIOCSUSAGE:
+ if (uref->usage_index >= field->report_count)
+ goto inval;
field->value[uref->usage_index] = uref->value;
goto goodreturn;
--
2.25.1
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