Re: [PATCH] ath11k: Fix potential RCU dereference issue in ath11k_debugfs_htt_ext_stats_handler

[Jeff Johnson]

On 8/30/2024 5:02 AM, Jiawei Ye wrote:
> In the `ath11k_debugfs_htt_ext_stats_handler` function, the `ar` pointer
> obtained via RCU lock is accessed after the RCU read-side critical
> section might be unlocked. According to RCU usage rules, this is illegal.
> Reusing this pointer can lead to unpredictable behavior, including
> accessing memory that has been updated or causing use-after-free issues.
> The `ath12k_debugfs_htt_ext_stats_handler` function in the
> `drivers/net/wireless/ath/ath12k/debugfs_htt_stats.c` file provides a good
> example to follow for addressing this issue.
> 
> This possible bug was identified using a static analysis tool developed
> by myself, specifically designed to detect RCU-related issues.
> 
> To address this issue, the RCU read lock is now kept until all accesses
> to the `ar` pointer are completed. A `goto exit` statement is introduced
> to ensure that the RCU read unlock is called appropriately, regardless of
> the function's exit path.

This analysis is incorrect since ar is not an RCU-protected structure

The rcu_read_lock() is required internally within
ath11k_mac_get_ar_by_pdev_id() when retrieving the RCU-protected pdev pointer.

So NAK this patch.