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Subject[PATCH] HID: debug: check length before copy_to_user()
Date
If our length is greater than the size of the buffer, we
overflow the buffer

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Cc: stable@vger.kernel.org
---
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
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