2023-10-23 11:14:12

by Greg Kroah-Hartman

[permalink] [raw]
Subject: [PATCH 6.5 239/241] Bluetooth: hci_sock: Correctly bounds check and pad HCI_MON_NEW_INDEX name

6.5-stable review patch. If anyone has any objections, please let me know.


From: Kees Cook <[email protected]>

commit cb3871b1cd135a6662b732fbc6b3db4afcdb4a64 upstream.

The code pattern of memcpy(dst, src, strlen(src)) is almost always
wrong. In this case it is wrong because it leaves memory uninitialized
if it is less than sizeof(ni->name), and overflows ni->name when longer.

Normally strtomem_pad() could be used here, but since ni->name is a
trailing array in struct hci_mon_new_index, compilers that don't support
-fstrict-flex-arrays=3 can't tell how large this array is via
__builtin_object_size(). Instead, open-code the helper and use sizeof()
since it will work correctly.

Additionally mark ni->name as __nonstring since it appears to not be a
%NUL terminated C string.

Cc: Luiz Augusto von Dentz <[email protected]>
Cc: Edward AD <[email protected]>
Cc: Marcel Holtmann <[email protected]>
Cc: Johan Hedberg <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Paolo Abeni <[email protected]>
Cc: [email protected]
Cc: [email protected]
Fixes: 18f547f3fc07 ("Bluetooth: hci_sock: fix slab oob read in create_monitor_event")
Link: https://lore.kernel.org/lkml/202310110908.F2639D3276@keescook/
Signed-off-by: Kees Cook <[email protected]>
Signed-off-by: Luiz Augusto von Dentz <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
include/net/bluetooth/hci_mon.h | 2 +-
net/bluetooth/hci_sock.c | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)

--- a/include/net/bluetooth/hci_mon.h
+++ b/include/net/bluetooth/hci_mon.h
@@ -56,7 +56,7 @@ struct hci_mon_new_index {
__u8 type;
__u8 bus;
bdaddr_t bdaddr;
- char name[8];
+ char name[8] __nonstring;
} __packed;

--- a/net/bluetooth/hci_sock.c
+++ b/net/bluetooth/hci_sock.c
@@ -439,7 +439,8 @@ static struct sk_buff *create_monitor_ev
ni->type = hdev->dev_type;
ni->bus = hdev->bus;
bacpy(&ni->bdaddr, &hdev->bdaddr);
- memcpy(ni->name, hdev->name, strlen(hdev->name));
+ memcpy_and_pad(ni->name, sizeof(ni->name), hdev->name,
+ strnlen(hdev->name, sizeof(ni->name)), '\0');

opcode = cpu_to_le16(HCI_MON_NEW_INDEX);