From: "Christian König" <ckoenig.leichtzumerken@gmail.com> To: cuigaosheng <cuigaosheng1@huawei.com>, "Christian König" <christian.koenig@amd.com>, "Charan Teja Kalla" <quic_charante@quicinc.com>, "T.J. Mercier" <tjmercier@google.com> Cc: sumit.semwal@linaro.org, Dan Carpenter <dan.carpenter@oracle.com>, Pavan Kondeti <quic_pkondeti@quicinc.com>, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org Subject: Re: [Linaro-mm-sig] Re: [PATCH] dma-buf: Fix possible UAF in dma_buf_export Date: Thu, 24 Nov 2022 13:55:39 +0100 [thread overview] Message-ID: <3de513b2-8ec3-2ff4-136d-0f56ac07c0ff@gmail.com> (raw) In-Reply-To: <a87e407c-f858-28f1-c5ea-ca69b39db53a@huawei.com> Am 24.11.22 um 13:49 schrieb cuigaosheng: >> I was already wondering why the order is this way. >> >> Why is dma_buf_stats_setup() needing the file in the first place? > > dmabuf->file will be used in dma_buf_stats_setup(), the > dma_buf_stats_setup() as follows: > >> 171 int dma_buf_stats_setup(struct dma_buf *dmabuf) >> 172 { >> 173 struct dma_buf_sysfs_entry *sysfs_entry; >> 174 int ret; >> 175 >> 176 if (!dmabuf || !dmabuf->file) >> 177 return -EINVAL; >> 178 >> 179 if (!dmabuf->exp_name) { >> 180 pr_err("exporter name must not be empty if stats >> needed\n"); >> 181 return -EINVAL; >> 182 } >> 183 >> 184 sysfs_entry = kzalloc(sizeof(struct dma_buf_sysfs_entry), >> GFP_KERNEL); >> 185 if (!sysfs_entry) >> 186 return -ENOMEM; >> 187 >> 188 sysfs_entry->kobj.kset = dma_buf_per_buffer_stats_kset; >> 189 sysfs_entry->dmabuf = dmabuf; >> 190 >> 191 dmabuf->sysfs_entry = sysfs_entry; >> 192 >> 193 /* create the directory for buffer stats */ >> 194 ret = kobject_init_and_add(&sysfs_entry->kobj, >> &dma_buf_ktype, NULL, >> 195 "%lu", >> file_inode(dmabuf->file)->i_ino); Ah, so it uses the i_ino of the file for the sysfs unique name. I'm going to take another look how to properly clean this up. Thanks for pointing this out, Christian. >> 196 if (ret) >> 197 goto err_sysfs_dmabuf; >> 198 >> 199 return 0; >> 200 >> 201 err_sysfs_dmabuf: >> 202 kobject_put(&sysfs_entry->kobj); >> 203 dmabuf->sysfs_entry = NULL; >> 204 return ret; >> 205 } > Did I miss something? > > Thanks. > > On 2022/11/24 20:37, Christian König wrote: >> >> >> Am 24.11.22 um 13:05 schrieb cuigaosheng: >>> Some tips: >>> Before we call the dma_buf_stats_setup(), we have to finish >>> creating the file, >>> otherwise dma_buf_stats_setup() will return -EINVAL, maybe we need >>> to think about >>> this when making a new patch. >> >> I was already wondering why the order is this way. >> >> Why is dma_buf_stats_setup() needing the file in the first place? >> >> Thanks, >> Christian. >> >>> >>> Hope these tips are useful, thanks! >>> >>> On 2022/11/24 13:56, Charan Teja Kalla wrote: >>>> Thanks T.J and Christian for the inputs. >>>> >>>> On 11/19/2022 7:00 PM, Christian König wrote: >>>>>> Yes, exactly that's the idea. >>>>>> >>>>>> The only alternatives I can see would be to either move >>>>>> allocating >>>>>> the >>>>>> file and so completing the dma_buf initialization last again >>>>>> or just >>>>>> ignore errors from sysfs. >>>>>> >>>>>> > If we still want to avoid calling >>>>>> dmabuf->ops->release(dmabuf) in >>>>>> > dma_buf_release like the comment says I guess we could use >>>>>> sysfs_entry >>>>>> > and ERR_PTR to flag that, otherwise it looks like we'd >>>>>> need a bit >>>>>> > somewhere. >>>>>> >>>>>> No, this should be dropped as far as I can see. The sysfs >>>>>> cleanup >>>>>> code >>>>>> looks like it can handle not initialized kobj pointers. >>>>>> >>>>>> >>>>>> Yeah there is also the null check in dma_buf_stats_teardown() that >>>>>> would prevent it from running, but I understood the comment to be >>>>>> referring to the release() dma_buf_ops call into the exporter which >>>>>> comes right after the teardown call. That looks like it's preventing >>>>>> the fput task work calling back into the exporter after the exporter >>>>>> already got an error from dma_buf_export(). Otherwise the exporter >>>>>> sees a release() for a buffer that it doesn't know about / thinks >>>>>> shouldn't exist. So I could imagine an exporter trying to double >>>>>> free: >>>>>> once for the failed dma_buf_export() call, and again when the >>>>>> release() op is called later. >>>>> >>>>> Oh, very good point as well. Yeah, then creating the file should >>>>> probably come last. >>>>> >>>> @Gaosheng: Could you please make these changes or you let me to do? >>>> >>>>> Regards, >>>>> Christian. >>>> . >> >> . > _______________________________________________ > Linaro-mm-sig mailing list -- linaro-mm-sig@lists.linaro.org > To unsubscribe send an email to linaro-mm-sig-leave@lists.linaro.org
WARNING: multiple messages have this Message-ID (diff)
From: "Christian König" <ckoenig.leichtzumerken@gmail.com> To: cuigaosheng <cuigaosheng1@huawei.com>, "Christian König" <christian.koenig@amd.com>, "Charan Teja Kalla" <quic_charante@quicinc.com>, "T.J. Mercier" <tjmercier@google.com> Cc: Pavan Kondeti <quic_pkondeti@quicinc.com>, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, sumit.semwal@linaro.org, Dan Carpenter <dan.carpenter@oracle.com>, linux-media@vger.kernel.org Subject: Re: [Linaro-mm-sig] Re: [PATCH] dma-buf: Fix possible UAF in dma_buf_export Date: Thu, 24 Nov 2022 13:55:39 +0100 [thread overview] Message-ID: <3de513b2-8ec3-2ff4-136d-0f56ac07c0ff@gmail.com> (raw) In-Reply-To: <a87e407c-f858-28f1-c5ea-ca69b39db53a@huawei.com> Am 24.11.22 um 13:49 schrieb cuigaosheng: >> I was already wondering why the order is this way. >> >> Why is dma_buf_stats_setup() needing the file in the first place? > > dmabuf->file will be used in dma_buf_stats_setup(), the > dma_buf_stats_setup() as follows: > >> 171 int dma_buf_stats_setup(struct dma_buf *dmabuf) >> 172 { >> 173 struct dma_buf_sysfs_entry *sysfs_entry; >> 174 int ret; >> 175 >> 176 if (!dmabuf || !dmabuf->file) >> 177 return -EINVAL; >> 178 >> 179 if (!dmabuf->exp_name) { >> 180 pr_err("exporter name must not be empty if stats >> needed\n"); >> 181 return -EINVAL; >> 182 } >> 183 >> 184 sysfs_entry = kzalloc(sizeof(struct dma_buf_sysfs_entry), >> GFP_KERNEL); >> 185 if (!sysfs_entry) >> 186 return -ENOMEM; >> 187 >> 188 sysfs_entry->kobj.kset = dma_buf_per_buffer_stats_kset; >> 189 sysfs_entry->dmabuf = dmabuf; >> 190 >> 191 dmabuf->sysfs_entry = sysfs_entry; >> 192 >> 193 /* create the directory for buffer stats */ >> 194 ret = kobject_init_and_add(&sysfs_entry->kobj, >> &dma_buf_ktype, NULL, >> 195 "%lu", >> file_inode(dmabuf->file)->i_ino); Ah, so it uses the i_ino of the file for the sysfs unique name. I'm going to take another look how to properly clean this up. Thanks for pointing this out, Christian. >> 196 if (ret) >> 197 goto err_sysfs_dmabuf; >> 198 >> 199 return 0; >> 200 >> 201 err_sysfs_dmabuf: >> 202 kobject_put(&sysfs_entry->kobj); >> 203 dmabuf->sysfs_entry = NULL; >> 204 return ret; >> 205 } > Did I miss something? > > Thanks. > > On 2022/11/24 20:37, Christian König wrote: >> >> >> Am 24.11.22 um 13:05 schrieb cuigaosheng: >>> Some tips: >>> Before we call the dma_buf_stats_setup(), we have to finish >>> creating the file, >>> otherwise dma_buf_stats_setup() will return -EINVAL, maybe we need >>> to think about >>> this when making a new patch. >> >> I was already wondering why the order is this way. >> >> Why is dma_buf_stats_setup() needing the file in the first place? >> >> Thanks, >> Christian. >> >>> >>> Hope these tips are useful, thanks! >>> >>> On 2022/11/24 13:56, Charan Teja Kalla wrote: >>>> Thanks T.J and Christian for the inputs. >>>> >>>> On 11/19/2022 7:00 PM, Christian König wrote: >>>>>> Yes, exactly that's the idea. >>>>>> >>>>>> The only alternatives I can see would be to either move >>>>>> allocating >>>>>> the >>>>>> file and so completing the dma_buf initialization last again >>>>>> or just >>>>>> ignore errors from sysfs. >>>>>> >>>>>> > If we still want to avoid calling >>>>>> dmabuf->ops->release(dmabuf) in >>>>>> > dma_buf_release like the comment says I guess we could use >>>>>> sysfs_entry >>>>>> > and ERR_PTR to flag that, otherwise it looks like we'd >>>>>> need a bit >>>>>> > somewhere. >>>>>> >>>>>> No, this should be dropped as far as I can see. The sysfs >>>>>> cleanup >>>>>> code >>>>>> looks like it can handle not initialized kobj pointers. >>>>>> >>>>>> >>>>>> Yeah there is also the null check in dma_buf_stats_teardown() that >>>>>> would prevent it from running, but I understood the comment to be >>>>>> referring to the release() dma_buf_ops call into the exporter which >>>>>> comes right after the teardown call. That looks like it's preventing >>>>>> the fput task work calling back into the exporter after the exporter >>>>>> already got an error from dma_buf_export(). Otherwise the exporter >>>>>> sees a release() for a buffer that it doesn't know about / thinks >>>>>> shouldn't exist. So I could imagine an exporter trying to double >>>>>> free: >>>>>> once for the failed dma_buf_export() call, and again when the >>>>>> release() op is called later. >>>>> >>>>> Oh, very good point as well. Yeah, then creating the file should >>>>> probably come last. >>>>> >>>> @Gaosheng: Could you please make these changes or you let me to do? >>>> >>>>> Regards, >>>>> Christian. >>>> . >> >> . > _______________________________________________ > Linaro-mm-sig mailing list -- linaro-mm-sig@lists.linaro.org > To unsubscribe send an email to linaro-mm-sig-leave@lists.linaro.org
next prev parent reply other threads:[~2022-11-24 12:56 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-11-17 6:21 [PATCH] dma-buf: Fix possible UAF in dma_buf_export Gaosheng Cui 2022-11-17 6:21 ` Gaosheng Cui 2022-11-17 7:48 ` Charan Teja Kalla 2022-11-17 7:48 ` Charan Teja Kalla 2022-11-17 10:16 ` Christian König 2022-11-17 10:16 ` Christian König 2022-11-18 2:36 ` T.J. Mercier 2022-11-18 2:36 ` T.J. Mercier 2022-11-18 8:27 ` Christian König 2022-11-18 8:27 ` Christian König 2022-11-18 17:05 ` T.J. Mercier 2022-11-19 13:30 ` Christian König 2022-11-24 5:56 ` Charan Teja Kalla 2022-11-24 5:56 ` Charan Teja Kalla 2022-11-24 11:31 ` cuigaosheng 2022-11-24 11:31 ` cuigaosheng 2022-11-24 12:05 ` cuigaosheng 2022-11-24 12:05 ` cuigaosheng 2022-11-24 12:37 ` Christian König 2022-11-24 12:37 ` Christian König 2022-11-24 12:49 ` cuigaosheng 2022-11-24 12:49 ` cuigaosheng 2022-11-24 12:55 ` Christian König [this message] 2022-11-24 12:55 ` [Linaro-mm-sig] " Christian König 2022-12-06 12:55 ` Charan Teja Kalla 2022-12-06 12:55 ` Charan Teja Kalla 2022-12-06 13:08 ` Christian König 2022-12-06 13:08 ` Christian König
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=3de513b2-8ec3-2ff4-136d-0f56ac07c0ff@gmail.com \ --to=ckoenig.leichtzumerken@gmail.com \ --cc=christian.koenig@amd.com \ --cc=cuigaosheng1@huawei.com \ --cc=dan.carpenter@oracle.com \ --cc=dri-devel@lists.freedesktop.org \ --cc=linaro-mm-sig@lists.linaro.org \ --cc=linux-media@vger.kernel.org \ --cc=quic_charante@quicinc.com \ --cc=quic_pkondeti@quicinc.com \ --cc=sumit.semwal@linaro.org \ --cc=tjmercier@google.com \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.