The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y git checkout FETCH_HEAD git cherry-pick -x 4d7b41c0e43995b0e992b9f8903109275744b658 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2024052327-heap-jumble-2f4f@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^.. Possible dependencies: 4d7b41c0e439 ("Bluetooth: L2CAP: Fix slab-use-after-free in l2cap_connect()") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 4d7b41c0e43995b0e992b9f8903109275744b658 Mon Sep 17 00:00:00 2001 From: Sungwoo Kim <iam@xxxxxxxxxxxx> Date: Tue, 30 Apr 2024 02:32:10 -0400 Subject: [PATCH] Bluetooth: L2CAP: Fix slab-use-after-free in l2cap_connect() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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@xxxxxxxxxxxx> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@xxxxxxxxx> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 84fc70862d78..868a370a16aa 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -3902,13 +3902,12 @@ static inline int l2cap_command_rej(struct l2cap_conn *conn, 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); @@ -3921,7 +3920,7 @@ static struct l2cap_chan *l2cap_connect(struct l2cap_conn *conn, &conn->hcon->dst, ACL_LINK); if (!pchan) { result = L2CAP_CR_BAD_PSM; - goto sendresp; + goto response; } mutex_lock(&conn->chan_lock); @@ -4008,17 +4007,15 @@ static struct l2cap_chan *l2cap_connect(struct l2cap_conn *conn, } 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); @@ -4041,7 +4038,9 @@ static struct l2cap_chan *l2cap_connect(struct l2cap_conn *conn, 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,
