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[42.60.144.185]) by smtp.gmail.com with ESMTPSA id y12sm1672446pgk.7.2021.07.29.10.42.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Jul 2021 10:42:56 -0700 (PDT) Subject: Re: memory leak in h4_recv_buf To: Marcel Holtmann , Dan Carpenter Cc: syzkaller-bugs , Johan Hedberg , linux-bluetooth , linux-kernel@vger.kernel.org References: <0000000000006b1779058c0cbdda@google.com> <20210729120706.GU1931@kadam> From: Phi Nguyen Message-ID: <15df8c9d-8809-7da3-842b-a65bfb06abeb@gmail.com> Date: Fri, 30 Jul 2021 01:42:52 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/29/2021 11:39 PM, Marcel Holtmann wrote: > Hi Dan, > >>>>> syzbot found the following crash on: >>>>> HEAD commit: abf02e29 Merge tag 'pm-5.2-rc6' of >>>>> git://git.kernel.org/pu .. >>>>> git tree: upstream >>>>> console output: >>>>> https://syzkaller.appspot.com/x/log.txt?x=1054e6b2a00000 >>>>> >>>>> kernel config: >>>>> https://syzkaller.appspot.com/x/.config?x=56f1da14935c3cce >>>>> >>>>> dashboard link: >>>>> 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 >>>>> >>>>> C reproducer: >>>>> 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 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 for how >>>>> to communicate with syzbot. >>>>> syzbot can test patches for this bug, for details see: >>>>> https://goo.gl/tpsmEJ#testing-patches >>>>> >>>>> -- >>>>> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. >>>>> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com . >>>>> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/d71a274f-fdeb-4da1-898e-06f6944e04dan%40googlegroups.com . >>>> >>>> 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). >>> >>> I don’t have that commit in my Linus’ tree. Where is it? >>> >> >> There is a typo in the git hash. It should be: 7649faff1cfe4 ("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. >>> >>> That seems to be a larger problem in the TTY layer if its contract with its users have changed. >> >> The tiocsti() function has an ancient comment which suggests that the >> documentation has always been wrong. >> >> * FIXME: may race normal receive processing > > so what are we suppose to do now? Fix this in TTY layer or try to revert this patch? > > And does it have to be spinlock or can we use a mutex? My knowledge of the TTY internal are limited and thus, I have no idea what we need to do here. However h4_recv_buf needs to be protected against concurrently calls. > > Regards > > Marcel > Hi Marcel, So far, I have tested two fixes with syzbot The first one is to bring the spin lock back to hci_uart_tty_receive(). The second one is to use tty_buffer_lock_exclusive() in tiocsti() (I based on the document in tty_buffer.c). These two can work well with the syzbot. Regards, Phi