2018-07-03 00:01:20

by Daniel Rosenberg

Subject: [PATCH] HID: debug: check length before copy_to_user()

If our length is greater than the size of the buffer, we
overflow the buffer

Signed-off-by: Daniel Rosenberg <[email protected]>
Cc: [email protected]
---
drivers/hid/hid-debug.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
index 8469b6964ff64..b48100236df89 100644
--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -1154,6 +1154,8 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
goto out;
if (list->tail > list->head) {
len = list->tail - list->head;
+ if (len > count)
+ len = count;

if (copy_to_user(buffer + ret, &list->hid_debug_buf[list->head], len)) {
ret = -EFAULT;
@@ -1163,6 +1165,8 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
list->head += len;
} else {
len = HID_DEBUG_BUFSIZE - list->head;
+ if (len > count)
+ len = count;

if (copy_to_user(buffer, &list->hid_debug_buf[list->head], len)) {
ret = -EFAULT;
@@ -1170,7 +1174,9 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
}
list->head = 0;
ret += len;
- goto copy_rest;
+ count -= len;
+ if (count > 0)
+ goto copy_rest;
}

}
--
2.18.0.399.gad0ab374a1-goog

2018-07-03 07:53:46

by Benjamin Tissoires

Subject: Re: [PATCH] HID: debug: check length before copy_to_user()

On Tue, Jul 3, 2018 at 1:59 AM, Daniel Rosenberg <[email protected]> wrote:
> If our length is greater than the size of the buffer, we
> overflow the buffer
>
> Signed-off-by: Daniel Rosenberg <[email protected]>
> Cc: [email protected]
> ---

Looks good:
Reviewed-by: Benjamin Tissoires <[email protected]>

Cheers,
Benjamin

> drivers/hid/hid-debug.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
> index 8469b6964ff64..b48100236df89 100644
> --- a/drivers/hid/hid-debug.c
> +++ b/drivers/hid/hid-debug.c
> @@ -1154,6 +1154,8 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
> goto out;
> if (list->tail > list->head) {
> len = list->tail - list->head;
> + if (len > count)
> + len = count;
>
> if (copy_to_user(buffer + ret, &list->hid_debug_buf[list->head], len)) {
> ret = -EFAULT;
> @@ -1163,6 +1165,8 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
> list->head += len;
> } else {
> len = HID_DEBUG_BUFSIZE - list->head;
> + if (len > count)
> + len = count;
>
> if (copy_to_user(buffer, &list->hid_debug_buf[list->head], len)) {
> ret = -EFAULT;
> @@ -1170,7 +1174,9 @@ static ssize_t hid_debug_events_read(struct file *file, char __user *buffer,
> }
> list->head = 0;
> ret += len;
> - goto copy_rest;
> + count -= len;
> + if (count > 0)
> + goto copy_rest;
> }
>
> }
> --
> 2.18.0.399.gad0ab374a1-goog
>

2018-07-03 09:56:49

by Jiri Kosina

Subject: Re: [PATCH] HID: debug: check length before copy_to_user()

On Tue, 3 Jul 2018, Benjamin Tissoires wrote:

> > If our length is greater than the size of the buffer, we
> > overflow the buffer
> >
> > Signed-off-by: Daniel Rosenberg <[email protected]>
> > Cc: [email protected]
> > ---
>
> Looks good:
> Reviewed-by: Benjamin Tissoires <[email protected]>

Indeed, thanks a lot for fixing this. Now queued, I'll push it for 4.18.

--
Jiri Kosina
SUSE Labs

2018-07-05 00:47:58

by Al Viro

Subject: Re: [PATCH] HID: debug: check length before copy_to_user()

On Mon, Jul 02, 2018 at 04:59:37PM -0700, Daniel Rosenberg wrote:
> If our length is greater than the size of the buffer, we
> overflow the buffer

Hmm...

How about this:
buf = list->hid_debug_buf;
if (list->tail < list->head) {
ret = simple_read_from_buffer(buffer, count, &list->head,
buf, HID_DEBUG_BUFSIZE);
if (ret < 0)
break;
if (list->head != buf + HID_DEBUG_BUFSIZE)
break;
list->head = 0;
}
n = simple_read_from_buffer(buffer + ret, count - ret, &list->head,
buf, list->tail);
if (n >= 0)
ret += n;
if (list->head == buf + HID_DEBUG_BUFSIZE)
list->head = 0;
instead?