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Mon, 17 Oct 2022 18:16:05 -0700 (PDT) Received: from localhost ([159.226.94.113]) by smtp.gmail.com with ESMTPSA id b8-20020a170903228800b001830ed575c3sm7215952plh.117.2022.10.17.18.16.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Oct 2022 18:16:04 -0700 (PDT) From: Hawkins Jiawei To: luiz.dentz@gmail.com Cc: 18801353760@163.com, davem@davemloft.net, edumazet@google.com, johan.hedberg@gmail.com, kuba@kernel.org, linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, luiz.von.dentz@intel.com, marcel@holtmann.org, netdev@vger.kernel.org, pabeni@redhat.com, syzbot+8f819e36e01022991cfa@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com, yin31149@gmail.com Subject: Re: [PATCH] Bluetooth: L2CAP: Fix memory leak in vhci_write Date: Tue, 18 Oct 2022 09:16:00 +0800 Message-Id: <20221018011601.3619-1-yin31149@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org On Tue, 18 Oct 2022 at 04:01, Luiz Augusto von Dentz wrote: > > Hi Hawkins, > > On Mon, Oct 17, 2022 at 12:47 AM Hawkins Jiawei wrote: > > > > Syzkaller reports a memory leak as follows: > > ==================================== > > BUG: memory leak > > unreferenced object 0xffff88810d81ac00 (size 240): > >   [...] > >   hex dump (first 32 bytes): > >     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................ > >     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................ > >   backtrace: > >     [] __alloc_skb+0x1f9/0x270 net/core/skbuff.c:418 > >     [] alloc_skb include/linux/skbuff.h:1257 [inline] > >     [] bt_skb_alloc include/net/bluetooth/bluetooth.h:469 [inline] > >     [] vhci_get_user drivers/bluetooth/hci_vhci.c:391 [inline] > >     [] vhci_write+0x5f/0x230 drivers/bluetooth/hci_vhci.c:511 > >     [] call_write_iter include/linux/fs.h:2192 [inline] > >     [] new_sync_write fs/read_write.c:491 [inline] > >     [] vfs_write+0x42d/0x540 fs/read_write.c:578 > >     [] ksys_write+0x9d/0x160 fs/read_write.c:631 > >     [] do_syscall_x64 arch/x86/entry/common.c:50 [inline] > >     [] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > >     [] entry_SYSCALL_64_after_hwframe+0x63/0xcd > > ==================================== > > > > HCI core will uses hci_rx_work() to process frame, which is queued to > > the hdev->rx_q tail in hci_recv_frame() by HCI driver. > > > > Yet the problem is that, HCI core does not free the skb after handling > > ACL data packets. To be more specific, when start fragment does not > > contain the L2CAP length, HCI core just reads possible bytes and > > finishes frame process in l2cap_recv_acldata(), without freeing the skb, > > which triggers the above memory leak. > > > > This patch solves it by releasing the relative skb, after processing the > > above case in l2cap_recv_acldata() > > > > Fixes: 4d7ea8ee90e4 ("Bluetooth: L2CAP: Fix handling fragmented length") > > Link: https://lore.kernel.org/all/0000000000000d0b1905e6aaef64@google.com/ > > Reported-and-tested-by: syzbot+8f819e36e01022991cfa@syzkaller.appspotmail.com > > Signed-off-by: Hawkins Jiawei > > --- > >  net/bluetooth/l2cap_core.c | 7 +++---- > >  1 file changed, 3 insertions(+), 4 deletions(-) > > > > diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c > > index 1f34b82ca0ec..e0a00854c02e 100644 > > --- a/net/bluetooth/l2cap_core.c > > +++ b/net/bluetooth/l2cap_core.c > > @@ -8426,9 +8426,8 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags) > >                  * expected length. > >                  */ > >                 if (skb->len < L2CAP_LEN_SIZE) { > > -                       if (l2cap_recv_frag(conn, skb, conn->mtu) < 0) > > -                               goto drop; > > -                       return; > > +                       l2cap_recv_frag(conn, skb, conn->mtu); > > +                       goto drop; > > Let us use break; instead of goto drop since we have copied the skb into rx_sbk. Thanks for your suggestion. I will refactor this patch as you suggested. > > >                 } > > > >                 len = get_unaligned_le16(skb->data) + L2CAP_HDR_SIZE; > > @@ -8472,7 +8471,7 @@ void l2cap_recv_acldata(struct hci_conn *hcon, struct sk_buff *skb, u16 flags) > > > >                         /* Header still could not be read just continue */ > >                         if (conn->rx_skb->len < L2CAP_LEN_SIZE) > > -                               return; > > +                               goto drop; > >                 } > > > >                 if (skb->len > conn->rx_len) { > > -- > > 2.25.1 > > > > > -- > Luiz Augusto von Dentz