From: Shuah Khan <skhan@linuxfoundation.org>
To: Anirudh Rayabharam <mail@anirudhrb.com>,
mcgrof@kernel.org, gregkh@linuxfoundation.org, rafael@kernel.org
Cc: linux-kernel@vger.kernel.org,
linux-kernel-mentees@lists.linuxfoundation.org,
syzbot+de271708674e2093097b@syzkaller.appspotmail.com,
Shuah Khan <skhan@linuxfoundation.org>
Subject: Re: [PATCH v7 2/2] firmware_loader: fix use-after-free in firmware_fallback_sysfs
Date: Mon, 26 Jul 2021 11:22:11 -0600 [thread overview]
Message-ID: <2f6f4318-8640-7b22-5492-e74f2af9ba38@linuxfoundation.org> (raw)
In-Reply-To: <20210724121134.6364-3-mail@anirudhrb.com>
On 7/24/21 6:11 AM, Anirudh Rayabharam wrote:
> This use-after-free happens when a fw_priv object has been freed but
> hasn't been removed from the pending list (pending_fw_head). The next
> time fw_load_sysfs_fallback tries to insert into the list, it ends up
> accessing the pending_list member of the previoiusly freed fw_priv.
>
> The root cause here is that all code paths that abort the fw load
> don't delete it from the pending list. For example:
>
> _request_firmware()
> -> fw_abort_batch_reqs()
> -> fw_state_aborted()
>
> To fix this, delete the fw_priv from the list in __fw_set_state() if
> the new state is DONE or ABORTED. This way, all aborts will remove
> the fw_priv from the list. Accordingly, remove calls to list_del_init
> that were being made before calling fw_state_(aborted|done).
>
> Also, in fw_load_sysfs_fallback, don't add the fw_priv to the pending
> list if it is already aborted. Instead, just jump out and return early.
>
> Fixes: bcfbd3523f3c ("firmware: fix a double abort case with fw_load_sysfs_fallback")
> Reported-by: syzbot+de271708674e2093097b@syzkaller.appspotmail.com
> Tested-by: syzbot+de271708674e2093097b@syzkaller.appspotmail.com
> Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> ---
> drivers/base/firmware_loader/fallback.c | 10 +++++++---
> drivers/base/firmware_loader/firmware.h | 6 +++++-
> drivers/base/firmware_loader/main.c | 2 ++
> 3 files changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
> index 1a48be0a030e..5d9f372fc9e7 100644
> --- a/drivers/base/firmware_loader/fallback.c
> +++ b/drivers/base/firmware_loader/fallback.c
> @@ -91,10 +91,9 @@ static void __fw_load_abort(struct fw_priv *fw_priv)
> * There is a small window in which user can write to 'loading'
> * between loading done and disappearance of 'loading'
> */
Update the comment to "between loading done/abort"
Rest looks good to me.
> - if (fw_sysfs_done(fw_priv))
> + if (fw_state_is_aborted(fw_priv) || fw_sysfs_done(fw_priv))
> return;
>
> - list_del_init(&fw_priv->pending_list);
> fw_state_aborted(fw_priv);
> }
>
> @@ -280,7 +279,6 @@ static ssize_t firmware_loading_store(struct device *dev,
> * Same logic as fw_load_abort, only the DONE bit
> * is ignored and we set ABORT only on failure.
> */
> - list_del_init(&fw_priv->pending_list);
> if (rc) {
> fw_state_aborted(fw_priv);
> written = rc;
> @@ -513,6 +511,11 @@ static int fw_load_sysfs_fallback(struct fw_sysfs *fw_sysfs, long timeout)
> }
>
> mutex_lock(&fw_lock);
> + if (fw_state_is_aborted(fw_priv)) {
> + mutex_unlock(&fw_lock);
> + retval = -EINTR;
> + goto out;
> + }
> list_add(&fw_priv->pending_list, &pending_fw_head);
> mutex_unlock(&fw_lock);
>
> @@ -538,6 +541,7 @@ static int fw_load_sysfs_fallback(struct fw_sysfs *fw_sysfs, long timeout)
> } else if (fw_priv->is_paged_buf && !fw_priv->data)
> retval = -ENOMEM;
>
> +out:
> device_del(f_dev);
> err_put_dev:
> put_device(f_dev);
> diff --git a/drivers/base/firmware_loader/firmware.h b/drivers/base/firmware_loader/firmware.h
> index 63bd29fdcb9c..36bdb413c998 100644
> --- a/drivers/base/firmware_loader/firmware.h
> +++ b/drivers/base/firmware_loader/firmware.h
> @@ -117,8 +117,12 @@ static inline void __fw_state_set(struct fw_priv *fw_priv,
>
> WRITE_ONCE(fw_st->status, status);
>
> - if (status == FW_STATUS_DONE || status == FW_STATUS_ABORTED)
> + if (status == FW_STATUS_DONE || status == FW_STATUS_ABORTED) {
> +#ifdef CONFIG_FW_LOADER_USER_HELPER
Might be helpful to add a comment that this covers all abort/done
paths
> + list_del_init(&fw_priv->pending_list);
> +#endif
> complete_all(&fw_st->completion);
> + }
> }
>
> static inline void fw_state_aborted(struct fw_priv *fw_priv)
> diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
> index 4fdb8219cd08..68c549d71230 100644
> --- a/drivers/base/firmware_loader/main.c
> +++ b/drivers/base/firmware_loader/main.c
> @@ -783,8 +783,10 @@ static void fw_abort_batch_reqs(struct firmware *fw)
> return;
>
> fw_priv = fw->priv;
> + mutex_lock(&fw_lock);
> if (!fw_state_is_aborted(fw_priv))
> fw_state_aborted(fw_priv);
> + mutex_unlock(&fw_lock);
> }
>
> /* called from request_firmware() and request_firmware_work_func() */
>
thanks,
-- Shuah
next prev parent reply other threads:[~2021-07-26 17:28 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-24 12:11 [PATCH v7 0/2] firmware_loader: fix uaf in firmware_fallback_sysfs Anirudh Rayabharam
2021-07-24 12:11 ` [PATCH v7 1/2] firmware_loader: use -ETIMEDOUT instead of -EAGAIN in fw_load_sysfs_fallback Anirudh Rayabharam
2021-07-26 16:56 ` Shuah Khan
2021-07-26 18:07 ` Luis Chamberlain
2021-07-24 12:11 ` [PATCH v7 2/2] firmware_loader: fix use-after-free in firmware_fallback_sysfs Anirudh Rayabharam
2021-07-26 17:22 ` Shuah Khan [this message]
2021-07-26 18:27 ` Luis Chamberlain
2021-07-27 12:57 ` Anirudh Rayabharam
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