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From:   Phi Nguyen <phind.uet@gmail.com>
Subject: Re: memory leak in h4_recv_buf
To:     syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        johan.hedberg@gmail.com, linux-bluetooth@vger.kernel.org,
        linux-kernel@vger.kernel.org, marcel@holtmann.org
References: <0000000000006b1779058c0cbdda@google.com>
 <d71a274f-fdeb-4da1-898e-06f6944e04dan@googlegroups.com>
Message-ID: <a125c3e6-7723-185a-3c47-219c201c6785@gmail.com>
Date:   Tue, 27 Jul 2021 23:05:14 +0800
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>     Hello,
> 
>     syzbot found the following crash on:
> 
>     HEAD commit: abf02e29 Merge tag 'pm-5.2-rc6' of
>     git://git.kernel.org/pu <http://git.kernel.org/pu>..
>     git tree: upstream
>     console output:
>     https://syzkaller.appspot.com/x/log.txt?x=1054e6b2a00000
>     <https://syzkaller.appspot.com/x/log.txt?x=1054e6b2a00000>
>     kernel config:
>     https://syzkaller.appspot.com/x/.config?x=56f1da14935c3cce
>     <https://syzkaller.appspot.com/x/.config?x=56f1da14935c3cce>
>     dashboard link:
>     https://syzkaller.appspot.com/bug?extid=97388eb9d31b997fe1d0
>     <https://syzkaller.appspot.com/bug?extid=97388eb9d31b997fe1d0>
>     compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>     syz repro:
>     https://syzkaller.appspot.com/x/repro.syz?x=1073d8aaa00000
>     <https://syzkaller.appspot.com/x/repro.syz?x=1073d8aaa00000>
>     C reproducer:
>     https://syzkaller.appspot.com/x/repro.c?x=17b36fbea00000
>     <https://syzkaller.appspot.com/x/repro.c?x=17b36fbea00000>
> 
>     IMPORTANT: if you fix the bug, please add the following tag to the
>     commit:
>     Reported-by: syzbot+97388e...@syzkaller.appspotmail.com
> 
>     program
>     BUG: memory leak
>     unreferenced object 0xffff88810991fa00 (size 224):
>     comm "syz-executor739", pid 7080, jiffies 4294949854 (age 18.640s)
>     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:
>     [<00000000da42c09f>] kmemleak_alloc_recursive
>     include/linux/kmemleak.h:43 [inline]
>     [<00000000da42c09f>] slab_post_alloc_hook mm/slab.h:439 [inline]
>     [<00000000da42c09f>] slab_alloc_node mm/slab.c:3269 [inline]
>     [<00000000da42c09f>] kmem_cache_alloc_node+0x153/0x2a0 mm/slab.c:3579
>     [<00000000f6fbcf84>] __alloc_skb+0x6e/0x210 net/core/skbuff.c:194
>     [<00000000ea93fc4c>] alloc_skb include/linux/skbuff.h:1054 [inline]
>     [<00000000ea93fc4c>] bt_skb_alloc include/net/bluetooth/bluetooth.h:339
>     [inline]
>     [<00000000ea93fc4c>] h4_recv_buf+0x26d/0x450
>     drivers/bluetooth/hci_h4.c:182
>     [<00000000e0312475>] h4_recv+0x51/0xb0 drivers/bluetooth/hci_h4.c:116
>     [<00000000ebf11fab>] hci_uart_tty_receive+0xba/0x200
>     drivers/bluetooth/hci_ldisc.c:592
>     [<0000000095e1216e>] tiocsti drivers/tty/tty_io.c:2195 [inline]
>     [<0000000095e1216e>] tty_ioctl+0x81c/0xa30 drivers/tty/tty_io.c:2571
>     [<000000009fa523f0>] vfs_ioctl fs/ioctl.c:46 [inline]
>     [<000000009fa523f0>] file_ioctl fs/ioctl.c:509 [inline]
>     [<000000009fa523f0>] do_vfs_ioctl+0x62a/0x810 fs/ioctl.c:696
>     [<000000000cebb5d9>] ksys_ioctl+0x86/0xb0 fs/ioctl.c:713
>     [<000000001630008a>] __do_sys_ioctl fs/ioctl.c:720 [inline]
>     [<000000001630008a>] __se_sys_ioctl fs/ioctl.c:718 [inline]
>     [<000000001630008a>] __x64_sys_ioctl+0x1e/0x30 fs/ioctl.c:718
>     [<00000000c62091e3>] do_syscall_64+0x76/0x1a0
>     arch/x86/entry/common.c:301
>     [<000000005c213625>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
>     BUG: memory leak
>     unreferenced object 0xffff8881204f4400 (size 1024):
>     comm "syz-executor739", pid 7080, jiffies 4294949854 (age 18.640s)
>     hex dump (first 32 bytes):
>     6c 69 62 75 64 65 76 00 fe ed ca fe 28 00 00 00 libudev.....(...
>     28 00 00 00 a0 00 00 00 52 ca da 77 00 00 00 00 (.......R..w....
>     backtrace:
>     [<0000000034504843>] kmemleak_alloc_recursive
>     include/linux/kmemleak.h:43 [inline]
>     [<0000000034504843>] slab_post_alloc_hook mm/slab.h:439 [inline]
>     [<0000000034504843>] slab_alloc_node mm/slab.c:3269 [inline]
>     [<0000000034504843>] kmem_cache_alloc_node_trace+0x15b/0x2a0
>     mm/slab.c:3597
>     [<0000000056d30eb5>] __do_kmalloc_node mm/slab.c:3619 [inline]
>     [<0000000056d30eb5>] __kmalloc_node_track_caller+0x38/0x50
>     mm/slab.c:3634
>     [<00000000df40176c>] __kmalloc_reserve.isra.0+0x40/0xb0
>     net/core/skbuff.c:138
>     [<0000000035340e64>] __alloc_skb+0xa0/0x210 net/core/skbuff.c:206
>     [<00000000ea93fc4c>] alloc_skb include/linux/skbuff.h:1054 [inline]
>     [<00000000ea93fc4c>] bt_skb_alloc include/net/bluetooth/bluetooth.h:339
>     [inline]
>     [<00000000ea93fc4c>] h4_recv_buf+0x26d/0x450
>     drivers/bluetooth/hci_h4.c:182
>     [<00000000e0312475>] h4_recv+0x51/0xb0 drivers/bluetooth/hci_h4.c:116
>     [<00000000ebf11fab>] hci_uart_tty_receive+0xba/0x200
>     drivers/bluetooth/hci_ldisc.c:592
>     [<0000000095e1216e>] tiocsti drivers/tty/tty_io.c:2195 [inline]
>     [<0000000095e1216e>] tty_ioctl+0x81c/0xa30 drivers/tty/tty_io.c:2571
>     [<000000009fa523f0>] vfs_ioctl fs/ioctl.c:46 [inline]
>     [<000000009fa523f0>] file_ioctl fs/ioctl.c:509 [inline]
>     [<000000009fa523f0>] do_vfs_ioctl+0x62a/0x810 fs/ioctl.c:696
>     [<000000000cebb5d9>] ksys_ioctl+0x86/0xb0 fs/ioctl.c:713
>     [<000000001630008a>] __do_sys_ioctl fs/ioctl.c:720 [inline]
>     [<000000001630008a>] __se_sys_ioctl fs/ioctl.c:718 [inline]
>     [<000000001630008a>] __x64_sys_ioctl+0x1e/0x30 fs/ioctl.c:718
>     [<00000000c62091e3>] do_syscall_64+0x76/0x1a0
>     arch/x86/entry/common.c:301
>     [<000000005c213625>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> 
> 
>     ---
>     This bug is generated by a bot. It may contain errors.
>     See https://goo.gl/tpsmEJ <https://goo.gl/tpsmEJ> for more
>     information about syzbot.
>     syzbot engineers can be reached at syzk...@googlegroups.com.
> 
>     syzbot will keep track of this bug report. See:
>     https://goo.gl/tpsmEJ#status <https://goo.gl/tpsmEJ#status> for how
>     to communicate with syzbot.
>     syzbot can test patches for this bug, for details see:
>     https://goo.gl/tpsmEJ#testing-patches
>     <https://goo.gl/tpsmEJ#testing-patches>
> 
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The reason of this memory leak is tty_ldisc_receive_buf() and tiocsti()
can access the h4->rx_skb concurrently by calling
hci_uart_tty_receive(), so the rx_skb be overwritten without
deallocating. There used to be an spin_lock in hci_uart_tty_receive(),
but it was removed by commit 7649ffaff1cfe(Bluetooth: Remove useless
rx_lock spinlock).

The commit message claims that hci_uart_tty_receive() was only called by
flush_to_ldisc(), but it seems incorrect.