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: syzbot+de271708674e2093097b@syzkaller.appspotmail.com
Tested-by: syzbot+de271708674e2093097b@syzkaller.appspotmail.com
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
Link: https://lore.kernel.org/r/20210728085107.4141-3-mail@anirudhrb.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
index 885e942178a3941c4cac7febb274d3d6e4737bf5..821e27bda4ca21c06e9621b750d9339952d7467d 100644 (file)
--- a/drivers/base/firmware_loader/fallback.c
+++ b/drivers/base/firmware_loader/fallback.c
@@ -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);
 }
 
@@ -297,7 +296,6 @@ 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;
@@ -559,6 +557,11 @@ 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);
 
@@ -584,6 +587,7 @@ 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);

diff --git a/drivers/base/firmware_loader/firmware.h b/drivers/base/firmware_loader/firmware.h
index 4c1395f8e7ed25d8dd623e888614a37b88eb071d..e2000b4ad09b3c794adccb8148455306d1d33db5 100644 (file)
--- a/drivers/base/firmware_loader/firmware.h
+++ b/drivers/base/firmware_loader/firmware.h
@@ -106,8 +106,16 @@ 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)

diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index 8e9213b36e31371aed574de0252366f171e6104f..24410a0d6df075a7fb1a72760adcaacb7c577620 100644 (file)
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -558,8 +558,10 @@ 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() */