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Commit d0963952 authored by Anirudh Rayabharam's avatar Anirudh Rayabharam Committed by Greg Kroah-Hartman
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firmware_loader: fix use-after-free in firmware_fallback_sysfs 



commit 75d95e2e39b27f733f21e6668af1c9893a97de5e upstream.

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 previously 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")
Cc: stable <stable@vger.kernel.org>
Reported-by: default avatar <syzbot+de271708674e2093097b@syzkaller.appspotmail.com>
Tested-by: default avatar <syzbot+de271708674e2093097b@syzkaller.appspotmail.com>
Reviewed-by: default avatarShuah Khan <skhan@linuxfoundation.org>
Acked-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
Signed-off-by: default avatarAnirudh Rayabharam <mail@anirudhrb.com>
Link: https://lore.kernel.org/r/20210728085107.4141-3-mail@anirudhrb.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1deb6b90

drivers/base/firmware_loader/fallback.c

+8 −4
Original line number Diff line number Diff line
@@ -86,12 +86,11 @@ 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'

	 * between loading done/aborted and disappearance of 'loading'

	 */

	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);

}
@@ -277,7 +276,6 @@ 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;
@@ -512,6 +510,11 @@ static int fw_load_sysfs_fallback(struct fw_sysfs *fw_sysfs, 
	}



	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);
@@ -537,6 +540,7 @@ static int fw_load_sysfs_fallback(struct fw_sysfs *fw_sysfs, 
	} else if (fw_priv->is_paged_buf && !fw_priv->data)

		retval = -ENOMEM;



out:

	device_del(f_dev);

err_put_dev:

	put_device(f_dev);

drivers/base/firmware_loader/firmware.h

+9 −1
Original line number Diff line number Diff line
@@ -108,9 +108,17 @@ 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

		/*

		 * Doing this here ensures that the fw_priv is deleted from

		 * the pending list in 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)

{

drivers/base/firmware_loader/main.c

+2 −0
Original line number Diff line number Diff line
@@ -747,8 +747,10 @@ 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() */