On Thu, Oct 14, 2010 at 5:37 PM, Gustavo F. Padovan
<padovan@xxxxxxxxxxxxxx> wrote:
> Hi Nathan,
>
> * Nathan Holstein <nathan.holstein@xxxxxxxxx> [2010-10-14 18:37:53 -0400]:
>
>> (Please keep me in the CC list, I'm not subscribed to lkml)
>>
>> [1] L2CAP module dereferences an uninitialized pointer within l2cap_connect_req.
>>
>> [2] I'm currently testing a 2.6.35 kernel on a Nexus One with backported
>> patches from bluetooth-2.6. When testing against certain BT devices, I'm seeing
>> a null-pointer deref. The crash is caused by this portion of commit e9aeb2dd:
>>
>> @@ -2966,6 +2991,15 @@ sendresp:
>> L2CAP_INFO_REQ, sizeof(info), &info);
>> }
>>
>> + if (!(l2cap_pi(sk)->conf_state & L2CAP_CONF_REQ_SENT) &&
>> + result == L2CAP_CR_SUCCESS) {
>> + u8 buf[128];
>> + l2cap_pi(sk)->conf_state |= L2CAP_CONF_REQ_SENT;
>> + l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
>> + l2cap_build_conf_req(sk, buf), buf);
>> + l2cap_pi(sk)->num_conf_req++;
>> + }
>> +
>> return 0;
>> }
>>
>> Multiple error cases jump to the response & sendresp labels prior to
>> initializing
>> the "sk" variable. In the case I'm currently seeing, the remote BT
>> device fails to
>> properly secure the ACL, making this crash 100% reproducible.
>>
>> [3] Bluetooth, L2CAP
>>
>> [4] This bug appears to be in the mainline 2.6.36-rc? kernel, in addition to
>> multiple Bluetooth development trees
>>
>> The following patch fixes the crash.
>>
>>
>> --nathan
>>
>> ---
>> In error cases when the ACL is insecure or we fail to allocate a new
>> struct sock, we jump to the "response" label. If so, "sk" will be
>> uninitialized and the kernel crashes.
>>
>> Signed-off-by: Nathan Holstein <nathan.holstein@xxxxxxxxx>
>> ---
>> net/bluetooth/l2cap.c | 4 ++--
>> 1 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
>> index d527b10..10ae0af 100644
>> --- a/net/bluetooth/l2cap.c
>> +++ b/net/bluetooth/l2cap.c
>> @@ -2911,7 +2911,7 @@ static inline int l2cap_connect_req(struct
>> l2cap_conn *conn, struct l2cap_cmd_hd
>> struct l2cap_chan_list *list = &conn->chan_list;
>> struct l2cap_conn_req *req = (struct l2cap_conn_req *) data;
>> struct l2cap_conn_rsp rsp;
>> - struct sock *parent, *uninitialized_var(sk);
>> + struct sock *parent, *sk = 0;
>
> Your fix is right, but please make *sk = NULL here.
> When I wrote that code I thought is was a false positive, but no, it's
> bug. :(
Updated patch below.
> --
> Gustavo F. Padovan
> ProFUSION embedded systems - http://profusion.mobi
>
---
In error cases when the ACL is insecure or we fail to allocate a new
struct sock, we jump to the "response" label. If so, "sk" will be
null and the kernel crashes.
Signed-off-by: Nathan Holstein <nathan.holstein@xxxxxxxxx>
---
net/bluetooth/l2cap.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index 4ded76e..4a4aa63 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -2911,7 +2911,7 @@ static inline int l2cap_connect_req(struct
l2cap_conn *conn, struct l2cap_cmd_hd
struct l2cap_chan_list *list = &conn->chan_list;
struct l2cap_conn_req *req = (struct l2cap_conn_req *) data;
struct l2cap_conn_rsp rsp;
- struct sock *parent, *uninitialized_var(sk);
+ struct sock *parent, *sk = NULL;
int result, status = L2CAP_CS_NO_INFO;
u16 dcid = 0, scid = __le16_to_cpu(req->scid);
@@ -3024,7 +3024,7 @@ sendresp:
L2CAP_INFO_REQ, sizeof(info), &info);
}
- if (!(l2cap_pi(sk)->conf_state & L2CAP_CONF_REQ_SENT) &&
+ if (sk && !(l2cap_pi(sk)->conf_state & L2CAP_CONF_REQ_SENT) &&
result == L2CAP_CR_SUCCESS) {
u8 buf[128];
l2cap_pi(sk)->conf_state |= L2CAP_CONF_REQ_SENT;
--
1.7.2.3
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