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 <redacted>
---
  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'
  	 */

-	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

+		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() */