From: Stefan Berger <stefanb@linux.ibm.com>
To: Lino Sanfilippo <LinoSanfilippo@gmx.de>,
peterhuewe@gmx.de, jarkko@kernel.org
Cc: jgg@ziepe.ca, stefanb@linux.vnet.ibm.com,
James.Bottomley@hansenpartnership.com, stable@vger.kernel.org,
linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
Lino Sanfilippo <l.sanfilippo@kunbus.com>
Subject: Re: [PATCH v3 1/2] tpm: fix reference counting for struct tpm_chip
Date: Thu, 4 Feb 2021 20:44:48 -0500 [thread overview]
Message-ID: <f5ad4381-773d-b994-51e5-a335ca4b44c3@linux.ibm.com> (raw)
In-Reply-To: <b36db793-9b40-92a8-19ef-4853ea10f775@linux.ibm.com>
On 2/4/21 7:46 PM, Stefan Berger wrote:
> On 2/4/21 6:50 PM, Lino Sanfilippo wrote:
>> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>
>> The following sequence of operations results in a refcount warning:
>>
>> 1. Open device /dev/tpmrm
>> 2. Remove module tpm_tis_spi
>> 3. Write a TPM command to the file descriptor opened at step 1.
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 3 PID: 1161 at lib/refcount.c:25 kobject_get+0xa0/0xa4
>> refcount_t: addition on 0; use-after-free.
>> Modules linked in: tpm_tis_spi tpm_tis_core tpm mdio_bcm_unimac brcmfmac
>> sha256_generic libsha256 sha256_arm hci_uart btbcm bluetooth cfg80211
>> vc4
>> brcmutil ecdh_generic ecc snd_soc_core crc32_arm_ce libaes
>> raspberrypi_hwmon ac97_bus snd_pcm_dmaengine bcm2711_thermal snd_pcm
>> snd_timer genet snd phy_generic soundcore [last unloaded: spi_bcm2835]
>> CPU: 3 PID: 1161 Comm: hold_open Not tainted 5.10.0ls-main-dirty #2
>> Hardware name: BCM2711
>> [<c0410c3c>] (unwind_backtrace) from [<c040b580>] (show_stack+0x10/0x14)
>> [<c040b580>] (show_stack) from [<c1092174>] (dump_stack+0xc4/0xd8)
>> [<c1092174>] (dump_stack) from [<c0445a30>] (__warn+0x104/0x108)
>> [<c0445a30>] (__warn) from [<c0445aa8>] (warn_slowpath_fmt+0x74/0xb8)
>> [<c0445aa8>] (warn_slowpath_fmt) from [<c08435d0>]
>> (kobject_get+0xa0/0xa4)
>> [<c08435d0>] (kobject_get) from [<bf0a715c>]
>> (tpm_try_get_ops+0x14/0x54 [tpm])
>> [<bf0a715c>] (tpm_try_get_ops [tpm]) from [<bf0a7d6c>]
>> (tpm_common_write+0x38/0x60 [tpm])
>> [<bf0a7d6c>] (tpm_common_write [tpm]) from [<c05a7ac0>]
>> (vfs_write+0xc4/0x3c0)
>> [<c05a7ac0>] (vfs_write) from [<c05a7ee4>] (ksys_write+0x58/0xcc)
>> [<c05a7ee4>] (ksys_write) from [<c04001a0>] (ret_fast_syscall+0x0/0x4c)
>> Exception stack(0xc226bfa8 to 0xc226bff0)
>> bfa0: 00000000 000105b4 00000003 beafe664 00000014
>> 00000000
>> bfc0: 00000000 000105b4 000103f8 00000004 00000000 00000000 b6f9c000
>> beafe684
>> bfe0: 0000006c beafe648 0001056c b6eb6944
>> ---[ end trace d4b8409def9b8b1f ]---
>>
>> The reason for this warning is the attempt to get the chip->dev
>> reference
>> in tpm_common_write() although the reference counter is already zero.
>>
>> Since commit 8979b02aaf1d ("tpm: Fix reference count to main device")
>> the
>> extra reference used to prevent a premature zero counter is never taken,
>> because the required TPM_CHIP_FLAG_TPM2 flag is never set.
>>
>> Fix this by removing the flag condition.
>>
>> Commit fdc915f7f719 ("tpm: expose spaces via a device link
>> /dev/tpmrm<n>")
>> already introduced function tpm_devs_release() to release the extra
>> reference but did not implement the required put on chip->devs that
>> results
>> in the call of this function.
>>
>> Fix this also by installing an action handler that puts chip->devs as
>> soon
>> as the chip is unregistered.
>>
>> Fixes: fdc915f7f719 ("tpm: expose spaces via a device link
>> /dev/tpmrm<n>")
>> Fixes: 8979b02aaf1d ("tpm: Fix reference count to main device")
>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>
> Tested-by: Stefan Berger <stefanb@linux.ibm.com>
>
> Steps:
>
> modprobe tpm_vtpm_proxy
>
> swtpm chardev --vtpm-proxy --tpm2 --tpmstate dir=./ &
>
> exec 100<>/dev/tpmrm1
>
> kill -9 <swtpm pid>
>
> rmmod tpm_vtpm_proxy
>
> exec 100>&- # fails before, works after --> great job! :-)
>
>
To clarify: When I tested this I had *both* patches applied. Without the
patches I got the null pointer exception in tpm2_del_space(). The 2nd
patch alone solves that issue when using the steps above.
[ 525.647443] [c000000005d3bba0] [c000000000e81d78]
mutex_lock+0x28/0x90 (unreliable)
[ 525.647539] [c000000005d3bbd0] [c0080000001f5da0]
tpm2_del_space+0x48/0x130 [tpm]
[ 525.647635] [c000000005d3bc20] [c0080000001f56b8]
tpmrm_release+0x40/0x70 [tpm]
[ 525.647746] [c000000005d3bc50] [c0000000004bf718] __fput+0xb8/0x340
[ 525.647842] [c000000005d3bca0] [c00000000017def4]
task_work_run+0xe4/0x150
[ 525.647930] [c000000005d3bcf0] [c00000000001feb4]
do_notify_resume+0x484/0x4f0
[ 525.648023] [c000000005d3bdb0] [c000000000033a64]
syscall_exit_prepare+0x1d4/0x330
[ 525.648115] [c000000005d3be20] [c00000000000d96c]
system_call_common+0xfc/0x27c
next prev parent reply other threads:[~2021-02-05 1:46 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-04 23:50 [PATCH v3 0/2] TPM fixes Lino Sanfilippo
2021-02-04 23:50 ` [PATCH v3 1/2] tpm: fix reference counting for struct tpm_chip Lino Sanfilippo
2021-02-05 0:46 ` Stefan Berger
2021-02-05 1:44 ` Stefan Berger [this message]
2021-02-05 2:01 ` James Bottomley
2021-02-05 10:52 ` Lino Sanfilippo
2021-02-05 13:29 ` Stefan Berger
2021-02-05 10:34 ` Lino Sanfilippo
2021-02-05 6:50 ` Greg KH
2021-02-05 13:05 ` Jason Gunthorpe
2021-02-05 14:55 ` Lino Sanfilippo
2021-02-05 15:15 ` Jason Gunthorpe
2021-02-05 15:50 ` Lino Sanfilippo
2021-02-05 15:58 ` Jason Gunthorpe
2021-02-05 21:50 ` Lino Sanfilippo
2021-02-06 0:39 ` Jason Gunthorpe
2021-02-04 23:50 ` [PATCH v3 2/2] tpm: in tpm2_del_space check if ops pointer is still valid Lino Sanfilippo
2021-02-05 0:34 ` James Bottomley
2021-02-05 2:18 ` Jarkko Sakkinen
2021-02-05 16:48 ` James Bottomley
2021-02-05 17:25 ` Jason Gunthorpe
2021-02-05 17:54 ` James Bottomley
2021-02-06 1:02 ` Jason Gunthorpe
2021-02-06 1:08 ` James Bottomley
2021-02-06 1:34 ` Jason Gunthorpe
2021-02-09 11:52 ` Lino Sanfilippo
2021-02-09 13:36 ` Jason Gunthorpe
2021-02-09 13:39 ` Lino Sanfilippo
2021-02-12 11:02 ` Jarkko Sakkinen
2021-02-12 10:59 ` Jarkko Sakkinen
2021-02-14 17:22 ` Lino Sanfilippo
2021-02-05 10:30 ` Lino Sanfilippo
2021-03-06 16:07 ` Lino Sanfilippo
2021-02-05 6:51 ` Greg KH
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