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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Wed, 4 Apr 2018 14:46:14 +0200
Message-ID: <CAPDyKFqD8vwuhebpOO6EfjzbdV_Mf+hbGZ5fLWOsVChMZ+w5XQ@mail.gmail.com>
Subject: Re: [PATCH] [mmc_block] Prevent bus reference leak in mmc_blk_init
To:     Shawn Lin <shawn.lin@rock-chips.com>,
        Alexander Kappner <agk@godking.net>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
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On 29 March 2018 at 11:52, Shawn Lin <shawn.lin@rock-chips.com> wrote:
> On 2018/3/29 6:18, Alexander Kappner wrote:
>>
>> Upon module load, mmc_block allocates a bus with bus_register in
>> mmc_blk_init. This reference never gets freed during module unload.
>> Subsequent re-insertions of the module fail and BUG() is triggered:
>
>
> WARN() is triggered.
>
>>
>> [   84.583342] sysfs: cannot create duplicate filename '/bus/mmc_rpmb'
>>
>> [   84.583373] CPU: 6 PID: 1825 Comm: modprobe Tainted: P           O
>> 4.16.0-rc6-00384-gf36b753 #30
>> [   84.583381] Hardware name: LENOVO 20ENCTO1WW/20ENCTO1WW, BIOS N1EET62W
>> (1.35 ) 11/10/2016
>> [   84.583385] Call Trace:
>> [   84.583401]  dump_stack+0x5a/0x75
>> [   84.583411]  sysfs_warn_dup+0x58/0x70
>> [   84.583419]  sysfs_create_dir_ns+0x70/0x80
>> [   84.583437]  kobject_add_internal+0xa5/0x2c0
>> [   84.583453]  kset_register+0x44/0x60
>> [   84.583470]  bus_register+0xc6/0x270
>> [   84.583479]  ? 0xffffffffa000d000
>> [   84.583492]  mmc_blk_init+0x12/0x1000 [mmc_block]
>> [   84.583501]  do_one_initcall+0x4e/0x194
>> [   84.583510]  ? ___cache_free+0x21/0x2b0
>> [   84.583524]  do_init_module+0x5a/0x20f
>> [   84.583533]  load_module+0x235c/0x2510
>> [   84.583550]  ? SYSC_finit_module+0x80/0xb0
>> [   84.583558]  SYSC_finit_module+0x80/0xb0
>> [   84.583570]  do_syscall_64+0x77/0x290
>> [   84.583580]  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
>> [   84.583587] RIP: 0033:0x7f452a3ad5b9
>> [   84.583593] RSP: 002b:00007fff4562ba18 EFLAGS: 00000206 ORIG_RAX:
>> 0000000000000139
>> [   84.583602] RAX: ffffffffffffffda RBX: 000056092895c520 RCX:
>> 00007f452a3ad5b9
>> [   84.583607] RDX: 0000000000000000 RSI: 000056092697b3d9 RDI:
>> 0000000000000003
>> [   84.583612] RBP: 000056092697b3d9 R08: 0000000000000000 R09:
>> 000056092895d310
>> [   84.583617] R10: 0000000000000003 R11: 0000000000000206 R12:
>> 0000000000000000
>> [   84.583623] R13: 000056092895c430 R14: 0000000000040000 R15:
>> 0000000000040000
>> [   84.583647] ------------[ cut here ]------------
>> [   84.583656] kobject_add_internal failed for mmc_rpmb with -EEXIST,
>> don't try to register things with the same name in the same directory.
>> [   84.583694] WARNING: CPU: 6 PID: 1825 at lib/kobject.c:238
>> kobject_add_internal+0x296/0x2c0
>> [   84.583705] Modules linked in: mmc_block(+) rtsx_pci_sdmmc rtsx_pci
>> iwlmvm mac80211 nvidia_drm(PO) nvidia_modeset(PO) iwlwifi nvidia(PO)
>> cfg80211 qmi_wwan thinkpad_acpi rfkill sdhci_pci cqhci sdhci mfd_core [last
>> unloaded: mmc_block]
>> [   84.583770] CPU: 6 PID: 1825 Comm: modprobe Tainted: P           O
>> 4.16.0-rc6-00384-gf36b753 #30
>> [   84.583774] Hardware name: LENOVO 20ENCTO1WW/20ENCTO1WW, BIOS N1EET62W
>> (1.35 ) 11/10/2016
>> [   84.583782] RIP: 0010:kobject_add_internal+0x296/0x2c0
>> [   84.583786] RSP: 0018:ffffc9000769bc58 EFLAGS: 00010296
>> [   84.583791] RAX: 000000000000007d RBX: ffff880fcf588618 RCX:
>> 0000000000000000
>> [   84.583796] RDX: 0000000000040400 RSI: 00000000000000f6 RDI:
>> 00000000ffffffff
>> [   84.583801] RBP: 00000000ffffffef R08: 0000000000000000 R09:
>> 0000000000000354
>> [   84.583806] R10: ffffffff8251fc74 R11: 0000000000000353 R12:
>> ffff88100d3cf698
>> [   84.583811] R13: ffff880fcf588618 R14: ffffffffa0028590 R15:
>> ffffffffa0028540
>> [   84.583818] FS:  00007f452a853700(0000) GS:ffff881053d80000(0000)
>> knlGS:0000000000000000
>> [   84.583823] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [   84.583837] CR2: 00007f452a3faea0 CR3: 0000000fc89e4004 CR4:
>> 00000000003606e0
>> [   84.583850] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
>> 0000000000000000
>> [   84.583863] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
>> 0000000000000400
>> [   84.583875] Call Trace:
>> [   84.583893]  kset_register+0x44/0x60
>> [   84.583902]  bus_register+0xc6/0x270
>> [   84.583910]  ? 0xffffffffa000d000
>> [   84.583926]  mmc_blk_init+0x12/0x1000 [mmc_block]
>> [   84.583940]  do_one_initcall+0x4e/0x194
>> [   84.583948]  ? ___cache_free+0x21/0x2b0
>> [   84.583966]  do_init_module+0x5a/0x20f
>> [   84.583979]  load_module+0x235c/0x2510
>> [   84.583995]  ? SYSC_finit_module+0x80/0xb0
>> [   84.584001]  SYSC_finit_module+0x80/0xb0
>> [   84.584010]  do_syscall_64+0x77/0x290
>> [   84.584016]  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
>> [   84.584021] RIP: 0033:0x7f452a3ad5b9
>> [   84.584025] RSP: 002b:00007fff4562ba18 EFLAGS: 00000206 ORIG_RAX:
>> 0000000000000139
>> [   84.584030] RAX: ffffffffffffffda RBX: 000056092895c520 RCX:
>> 00007f452a3ad5b9
>> [   84.584034] RDX: 0000000000000000 RSI: 000056092697b3d9 RDI:
>> 0000000000000003
>> [   84.584038] RBP: 000056092697b3d9 R08: 0000000000000000 R09:
>> 000056092895d310
>> [   84.584043] R10: 0000000000000003 R11: 0000000000000206 R12:
>> 0000000000000000
>> [   84.584047] R13: 000056092895c430 R14: 0000000000040000 R15:
>> 0000000000040000
>> [   84.584053] Code: 7b 20 49 89 c4 48 85 ff 0f 84 10 fe ff ff e9 cd fd ff
>> ff 48 8b 13 48 c7 c6 00 80 f4 81 48 c7 c7 e0 ad 0f 82 31 c0 e8 ca 9a 7b ff
>> <0f> 0b e9 5f fe ff ff 0f 0b 0f 0b 0f 0b 0f 0b e9 71 ff ff ff 0f
>> [   84.584147] ---[ end trace d27b36e0e2c0e7e5 ]---
>> [   84.584162] mmcblk: could not register RPMB bus type
>>
>> Steps to reproduce:
>>
>> Build with CONFIG_MMC_BLOCK=m
>>
>> modprobe mmc_block
>> rmmod mmc_block
>> modprobe mmc_block
>>
>> The proposed patch deallocates the reference in mmc_blk_exit.
>>
>
> Fixes: 97548575bef3 ("mmc: block: Convert RPMB to a character device")
> Cc: Stable <stable@vger.kernel.org>
>
>> Signed-off-by: Alexander Kappner <agk@godking.net>
>> ---
>>   drivers/mmc/core/block.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
>> index 2cfb963..9c6f639 100644
>> --- a/drivers/mmc/core/block.c
>> +++ b/drivers/mmc/core/block.c
>> @@ -3087,6 +3087,7 @@ static void __exit mmc_blk_exit(void)
>>         mmc_unregister_driver(&mmc_driver);
>>         unregister_blkdev(MMC_BLOCK_MAJOR, "mmc");
>>         unregister_chrdev_region(mmc_rpmb_devt, MAX_DEVICES);
>> +       bus_unregister(&mmc_rpmb_bus_type);
>
>
> Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
>
>>   }
>>     module_init(mmc_blk_init);
>>
>

Shawn, Alexander - thanks, applied for fixes!

Kind regards
Uffe