This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1][2].
As the "dl" variable is a pointer to "struct hci_dev_list_req" and this
structure ends in a flexible array:
struct hci_dev_list_req {
[...]
struct hci_dev_req dev_req[]; /* hci_dev_req structures */
};
the preferred way in the kernel is to use the struct_size() helper to
do the arithmetic instead of the calculation "size + count * size" in
the kzalloc() and copy_to_user() functions.
At the same time, prepare for the coming implementation by GCC and Clang
of the __counted_by attribute. Flexible array members annotated with
__counted_by can have their accesses bounds-checked at run-time via
CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for
strcpy/memcpy-family functions).
In this case, it is important to note that the logic needs a little
refactoring to ensure that the "dev_num" member is initialized before
the first access to the flex array. Specifically, add the assignment
before the list_for_each_entry() loop.
Also remove the "size" variable as it is no longer needed and refactor
the list_for_each_entry() loop to use dr[n] instead of (dr + n).
This way, the code is more readable, idiomatic and safer.
This code was detected with the help of Coccinelle, and audited and
modified manually.
Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
Link: https://github.com/KSPP/linux/issues/160 [2]
Signed-off-by: Erick Archer <erick.archer@xxxxxxxxxxx>
---
include/net/bluetooth/hci_sock.h | 2 +-
net/bluetooth/hci_core.c | 15 ++++++---------
2 files changed, 7 insertions(+), 10 deletions(-)
diff --git a/include/net/bluetooth/hci_sock.h b/include/net/bluetooth/hci_sock.h
index 9949870f7d78..13e8cd4414a1 100644
--- a/include/net/bluetooth/hci_sock.h
+++ b/include/net/bluetooth/hci_sock.h
@@ -144,7 +144,7 @@ struct hci_dev_req {
struct hci_dev_list_req {
__u16 dev_num;
- struct hci_dev_req dev_req[]; /* hci_dev_req structures */
+ struct hci_dev_req dev_req[] __counted_by(dev_num);
};
struct hci_conn_list_req {
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index adfd53a9fcd4..cae8a67bcd62 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -837,7 +837,7 @@ int hci_get_dev_list(void __user *arg)
struct hci_dev *hdev;
struct hci_dev_list_req *dl;
struct hci_dev_req *dr;
- int n = 0, size, err;
+ int n = 0, err;
__u16 dev_num;
if (get_user(dev_num, (__u16 __user *) arg))
@@ -846,12 +846,11 @@ int hci_get_dev_list(void __user *arg)
if (!dev_num || dev_num > (PAGE_SIZE * 2) / sizeof(*dr))
return -EINVAL;
- size = sizeof(*dl) + dev_num * sizeof(*dr);
-
- dl = kzalloc(size, GFP_KERNEL);
+ dl = kzalloc(struct_size(dl, dev_req, dev_num), GFP_KERNEL);
if (!dl)
return -ENOMEM;
+ dl->dev_num = dev_num;
dr = dl->dev_req;
read_lock(&hci_dev_list_lock);
@@ -865,8 +864,8 @@ int hci_get_dev_list(void __user *arg)
if (hci_dev_test_flag(hdev, HCI_AUTO_OFF))
flags &= ~BIT(HCI_UP);
- (dr + n)->dev_id = hdev->id;
- (dr + n)->dev_opt = flags;
+ dr[n].dev_id = hdev->id;
+ dr[n].dev_opt = flags;
if (++n >= dev_num)
break;
@@ -874,9 +873,7 @@ int hci_get_dev_list(void __user *arg)
read_unlock(&hci_dev_list_lock);
dl->dev_num = n;
- size = sizeof(*dl) + n * sizeof(*dr);
-
- err = copy_to_user(arg, dl, size);
+ err = copy_to_user(arg, dl, struct_size(dl, dev_req, n));
kfree(dl);
return err ? -EFAULT : 0;
--
2.25.1
