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firmware_loader: fix use-after-free in firmware_fallback_sysfs

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commit 75d95e2e39 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: bcfbd3523f ("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>
This commit is contained in:
Anirudh Rayabharam 2021-07-28 14:21:07 +05:30 committed by Greg Kroah-Hartman
parent 1deb6b9030
commit d09639528b
3 changed files with 19 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

12
drivers/base/firmware_loader/fallback.c
View file

@ -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);

10
drivers/base/firmware_loader/firmware.h
View file

@ -108,8 +108,16 @@ 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)

2
drivers/base/firmware_loader/main.c
View file

@ -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() */