6.8-stable review patch. If anyone has any objections, please let me know.
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From: Sungwoo Kim iam@sung-woo.kim
commit 4d7b41c0e43995b0e992b9f8903109275744b658 upstream.
Extend a critical section to prevent chan from early freeing. Also make the l2cap_connect() return type void. Nothing is using the returned value but it is ugly to return a potentially freed pointer. Making it void will help with backports because earlier kernels did use the return value. Now the compile will break for kernels where this patch is not a complete fix.
Call stack summary:
[use] l2cap_bredr_sig_cmd l2cap_connect ┌ mutex_lock(&conn->chan_lock); │ chan = pchan->ops->new_connection(pchan); <- alloc chan │ __l2cap_chan_add(conn, chan); │ l2cap_chan_hold(chan); │ list_add(&chan->list, &conn->chan_l); ... (1) └ mutex_unlock(&conn->chan_lock); chan->conf_state ... (4) <- use after free
[free] l2cap_conn_del ┌ mutex_lock(&conn->chan_lock); │ foreach chan in conn->chan_l: ... (2) │ l2cap_chan_put(chan); │ l2cap_chan_destroy │ kfree(chan) ... (3) <- chan freed └ mutex_unlock(&conn->chan_lock);
================================================================== BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline] BUG: KASAN: slab-use-after-free in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] BUG: KASAN: slab-use-after-free in l2cap_connect+0xa67/0x11a0 net/bluetooth/l2cap_core.c:4260 Read of size 8 at addr ffff88810bf040a0 by task kworker/u3:1/311
Fixes: 73ffa904b782 ("Bluetooth: Move conf_{req,rsp} stuff to struct l2cap_chan") Signed-off-by: Sungwoo Kim iam@sung-woo.kim Signed-off-by: Luiz Augusto von Dentz luiz.von.dentz@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/bluetooth/l2cap_core.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-)
--- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -3905,13 +3905,12 @@ static inline int l2cap_command_rej(stru return 0; }
-static struct l2cap_chan *l2cap_connect(struct l2cap_conn *conn, - struct l2cap_cmd_hdr *cmd, - u8 *data, u8 rsp_code, u8 amp_id) +static void l2cap_connect(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, + u8 *data, u8 rsp_code, u8 amp_id) { struct l2cap_conn_req *req = (struct l2cap_conn_req *) data; struct l2cap_conn_rsp rsp; - struct l2cap_chan *chan = NULL, *pchan; + struct l2cap_chan *chan = NULL, *pchan = NULL; int result, status = L2CAP_CS_NO_INFO;
u16 dcid = 0, scid = __le16_to_cpu(req->scid); @@ -3924,7 +3923,7 @@ static struct l2cap_chan *l2cap_connect( &conn->hcon->dst, ACL_LINK); if (!pchan) { result = L2CAP_CR_BAD_PSM; - goto sendresp; + goto response; }
mutex_lock(&conn->chan_lock); @@ -4011,17 +4010,15 @@ static struct l2cap_chan *l2cap_connect( }
response: - l2cap_chan_unlock(pchan); - mutex_unlock(&conn->chan_lock); - l2cap_chan_put(pchan); - -sendresp: rsp.scid = cpu_to_le16(scid); rsp.dcid = cpu_to_le16(dcid); rsp.result = cpu_to_le16(result); rsp.status = cpu_to_le16(status); l2cap_send_cmd(conn, cmd->ident, rsp_code, sizeof(rsp), &rsp);
+ if (!pchan) + return; + if (result == L2CAP_CR_PEND && status == L2CAP_CS_NO_INFO) { struct l2cap_info_req info; info.type = cpu_to_le16(L2CAP_IT_FEAT_MASK); @@ -4044,7 +4041,9 @@ sendresp: chan->num_conf_req++; }
- return chan; + l2cap_chan_unlock(pchan); + mutex_unlock(&conn->chan_lock); + l2cap_chan_put(pchan); }
static int l2cap_connect_req(struct l2cap_conn *conn,