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[142.162.113.129]) by smtp.gmail.com with ESMTPSA id n1-20020a05622a11c100b002dff3364c6esm4018049qtk.19.2022.03.04.09.52.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Mar 2022 09:52:30 -0800 (PST) Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1nQC6P-004xNx-T2; Fri, 04 Mar 2022 13:52:29 -0400 Date: Fri, 4 Mar 2022 13:52:29 -0400 From: Jason Gunthorpe To: Lino Sanfilippo Cc: peterhuewe@gmx.de, jarkko@kernel.org, stefanb@linux.vnet.ibm.com, James.Bottomley@hansenpartnership.com, David.Laight@ACULAB.COM, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, p.rosenberger@kunbus.com, Lino Sanfilippo , stable@vger.kernel.org, Stefan Berger Subject: Re: [PATCH v9 1/1] tpm: fix reference counting for struct tpm_chip Message-ID: <20220304175229.GH6468@ziepe.ca> References: <20220302094353.3465-1-LinoSanfilippo@gmx.de> <20220302094353.3465-2-LinoSanfilippo@gmx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220302094353.3465-2-LinoSanfilippo@gmx.de> Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Wed, Mar 02, 2022 at 10:43:53AM +0100, Lino Sanfilippo wrote: > From: Lino Sanfilippo > > 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 > [] (unwind_backtrace) from [] (show_stack+0x10/0x14) > [] (show_stack) from [] (dump_stack+0xc4/0xd8) > [] (dump_stack) from [] (__warn+0x104/0x108) > [] (__warn) from [] (warn_slowpath_fmt+0x74/0xb8) > [] (warn_slowpath_fmt) from [] (kobject_get+0xa0/0xa4) > [] (kobject_get) from [] (tpm_try_get_ops+0x14/0x54 [tpm]) > [] (tpm_try_get_ops [tpm]) from [] (tpm_common_write+0x38/0x60 [tpm]) > [] (tpm_common_write [tpm]) from [] (vfs_write+0xc4/0x3c0) > [] (vfs_write) from [] (ksys_write+0x58/0xcc) > [] (ksys_write) from [] (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 moving the TPM 2 character device handling from > tpm_chip_alloc() to tpm_add_char_device() which is called at a later point > in time when the flag has been set in case of TPM2. > > Commit fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm") > 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 by putting chip->devs in tpm_chip_unregister(). > > Finally move the new implementation for the TPM 2 handling into a new > function to avoid multiple checks for the TPM_CHIP_FLAG_TPM2 flag in the > good case and error cases. > > Cc: stable@vger.kernel.org > Fixes: fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm") > Fixes: 8979b02aaf1d ("tpm: Fix reference count to main device") > Co-developed-by: Jason Gunthorpe > Tested-by: Stefan Berger > Signed-off-by: Jason Gunthorpe > Signed-off-by: Lino Sanfilippo > --- > drivers/char/tpm/tpm-chip.c | 46 +++++-------------------- > drivers/char/tpm/tpm.h | 2 ++ > drivers/char/tpm/tpm2-space.c | 65 +++++++++++++++++++++++++++++++++++ > 3 files changed, 75 insertions(+), 38 deletions(-) Reviewed-by: Jason Gunthorpe Jason