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b674fb513e
Currently, the synchronization between ath9k_wmi_cmd() and
ath9k_wmi_ctrl_rx() is exposed to a race condition which, although being
rather unlikely, can lead to invalid behaviour of ath9k_wmi_cmd().
Consider the following scenario:
CPU0 CPU1
ath9k_wmi_cmd(...)
mutex_lock(&wmi->op_mutex)
ath9k_wmi_cmd_issue(...)
wait_for_completion_timeout(...)
---
timeout
---
/* the callback is being processed
* before last_seq_id became zero
*/
ath9k_wmi_ctrl_rx(...)
spin_lock_irqsave(...)
/* wmi->last_seq_id check here
* doesn't detect timeout yet
*/
spin_unlock_irqrestore(...)
/* last_seq_id is zeroed to
* indicate there was a timeout
*/
wmi->last_seq_id = 0
mutex_unlock(&wmi->op_mutex)
return -ETIMEDOUT
ath9k_wmi_cmd(...)
mutex_lock(&wmi->op_mutex)
/* the buffer is replaced with
* another one
*/
wmi->cmd_rsp_buf = rsp_buf
wmi->cmd_rsp_len = rsp_len
ath9k_wmi_cmd_issue(...)
spin_lock_irqsave(...)
spin_unlock_irqrestore(...)
wait_for_completion_timeout(...)
/* the continuation of the
* callback left after the first
* ath9k_wmi_cmd call
*/
ath9k_wmi_rsp_callback(...)
/* copying data designated
* to already timeouted
* WMI command into an
* inappropriate wmi_cmd_buf
*/
memcpy(...)
complete(&wmi->cmd_wait)
/* awakened by the bogus callback
* => invalid return result
*/
mutex_unlock(&wmi->op_mutex)
return 0
To fix this, update last_seq_id on timeout path inside ath9k_wmi_cmd()
under the wmi_lock. Move ath9k_wmi_rsp_callback() under wmi_lock inside
ath9k_wmi_ctrl_rx() so that the wmi->cmd_wait can be completed only for
initially designated wmi_cmd call, otherwise the path would be rejected
with last_seq_id check.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Fixes: fb9987d0f7 ("ath9k_htc: Support for AR9271 chipset.")
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230425192607.18015-1-pchelkin@ispras.ru
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.