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From:   John Stultz <john.stultz@linaro.org>
Date:   Tue, 19 Mar 2019 17:09:03 -0700
Message-ID: <CALAqxLUkw0iDq+mFk-MRDT5hQDx3e2eLZg_bGUyokst0zQma9Q@mail.gmail.com>
Subject: Re: [PATCH] usb: gadget: f_fs: don't free buffer prematurely
To:     fei.yang@intel.com
Cc:     Felipe Balbi <balbi@kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>, andrzej.p@collabora.com,
        Vincent Pelletier <plr.vincent@gmail.com>,
        jingx.shen@intel.com, Linux USB List <linux-usb@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Badhri Jagan Sridharan <badhri@google.com>,
        Josh Gao <jmgao@google.com>,
        Alistair Strachan <astrachan@google.com>,
        YongQin Liu <yongqin.liu@linaro.org>,
        Amit Pundir <amit.pundir@linaro.org>
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On Tue, Mar 19, 2019 at 4:25 PM <fei.yang@intel.com> wrote:
>
> From: Fei Yang <fei.yang@intel.com>
>
> The following kernel panic happens due to the io_data buffer gets dealloc=
ated
> before the async io is completed. Add a check for the case where io_data =
buffer
> should be deallocated by ffs_user_copy_worker.
>
> [   41.663334] BUG: unable to handle kernel NULL pointer dereference at 0=
000000000000048
> [   41.672099] #PF error: [normal kernel read fault]
> [   41.677356] PGD 20c974067 P4D 20c974067 PUD 20c973067 PMD 0
> [   41.683687] Oops: 0000 [#1] PREEMPT SMP
> [   41.687976] CPU: 1 PID: 7 Comm: kworker/u8:0 Tainted: G     U         =
   5.0.0-quilt-2e5dc0ac-00790-gd8c79f2-dirty #2
> [   41.705309] Workqueue: adb ffs_user_copy_worker
> [   41.705316] RIP: 0010:__vunmap+0x2a/0xc0
> [   41.705318] Code: 0f 1f 44 00 00 48 85 ff 0f 84 87 00 00 00 55 f7 c7 f=
f 0f 00 00 48 89 e5 41 55 41 89 f5 41 54 53 48 89 fb 75 71 e8 56 d7 ff ff <=
4c> 8b 60 48 4d 85 e4 74 76 48 89 df e8 25 ff ff ff 45 85 ed 74 46
> [   41.705320] RSP: 0018:ffffbc3a40053df0 EFLAGS: 00010286
> [   41.705322] RAX: 0000000000000000 RBX: ffffbc3a406f1000 RCX: 000000000=
0000000
> [   41.705323] RDX: 0000000000000001 RSI: 0000000000000001 RDI: 00000000f=
fffffff
> [   41.705324] RBP: ffffbc3a40053e08 R08: 000000000001fb79 R09: 000000000=
0000037
> [   41.705325] R10: ffffbc3a40053b68 R11: ffffbc3a40053cad R12: fffffffff=
ffffff2
> [   41.705326] R13: 0000000000000001 R14: 0000000000000000 R15: fffffffff=
fffffff
> [   41.705328] FS:  0000000000000000(0000) GS:ffff9e2977a80000(0000) knlG=
S:0000000000000000
> [   41.705329] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   41.705330] CR2: 0000000000000048 CR3: 000000020c994000 CR4: 000000000=
03406e0
> [   41.705331] Call Trace:
> [   41.705338]  vfree+0x50/0xb0
> [   41.705341]  ffs_user_copy_worker+0xe9/0x1c0
> [   41.705344]  process_one_work+0x19f/0x3e0
> [   41.705348]  worker_thread+0x3f/0x3b0
> [   41.829766]  kthread+0x12b/0x150
> [   41.833371]  ? process_one_work+0x3e0/0x3e0
> [   41.838045]  ? kthread_create_worker_on_cpu+0x70/0x70
> [   41.843695]  ret_from_fork+0x3a/0x50
> [   41.847689] Modules linked in: hci_uart bluetooth ecdh_generic rfkill_=
gpio dwc3_pci dwc3 snd_usb_audio mei_me tpm_crb snd_usbmidi_lib xhci_pci xh=
ci_hcd mei tpm snd_hwdep cfg80211 snd_soc_skl snd_soc_skl_ipc snd_soc_sst_i=
pc snd_soc_sst_dsp snd_hda_ext_core snd_hda_core videobuf2_dma_sg crlmodule
> [   41.876880] CR2: 0000000000000048
> [   41.880584] ---[ end trace 2bc4addff0f2e673 ]---
> [   41.891346] RIP: 0010:__vunmap+0x2a/0xc0
> [   41.895734] Code: 0f 1f 44 00 00 48 85 ff 0f 84 87 00 00 00 55 f7 c7 f=
f 0f 00 00 48 89 e5 41 55 41 89 f5 41 54 53 48 89 fb 75 71 e8 56 d7 ff ff <=
4c> 8b 60 48 4d 85 e4 74 76 48 89 df e8 25 ff ff ff 45 85 ed 74 46
> [   41.916740] RSP: 0018:ffffbc3a40053df0 EFLAGS: 00010286
> [   41.922583] RAX: 0000000000000000 RBX: ffffbc3a406f1000 RCX: 000000000=
0000000
> [   41.930563] RDX: 0000000000000001 RSI: 0000000000000001 RDI: 00000000f=
fffffff
> [   41.938540] RBP: ffffbc3a40053e08 R08: 000000000001fb79 R09: 000000000=
0000037
> [   41.946520] R10: ffffbc3a40053b68 R11: ffffbc3a40053cad R12: fffffffff=
ffffff2
> [   41.954502] R13: 0000000000000001 R14: 0000000000000000 R15: fffffffff=
fffffff
> [   41.962482] FS:  0000000000000000(0000) GS:ffff9e2977a80000(0000) knlG=
S:0000000000000000
> [   41.971536] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   41.977960] CR2: 0000000000000048 CR3: 000000020c994000 CR4: 000000000=
03406e0
> [   41.985930] Kernel panic - not syncing: Fatal exception
> [   41.991817] Kernel Offset: 0x16000000 from 0xffffffff81000000 (relocat=
ion range: 0xffffffff80000000-0xffffffffbfffffff)
> [   42.009525] Rebooting in 10 seconds..
> [   52.014376] ACPI MEMORY or I/O RESET_REG.
>
> Signed-off-by: Fei Yang <fei.yang@intel.com>

Awesome! Seems to resolve the crash I was seeing!

Tested-by: John Stultz <john.stultz@linaro.org>

Do be sure to mark it for -stable, as I was seeing crashes all the way
back to 4.9 (and it probably affects 4.4 too).

thanks
-john