[OpenWrt-Devel] Memory leak related to OpenWrt patch of hostapd

[Petr Štetiar]

Nick Schaf <nick.schaf at jci.com> [2019-07-31 16:34:36]:

Hi,

> I've noticed the wpa_supplicant process on my mesh interfaces leaking memory
> to the point that the kernel kills the process.  It was discovered in
> 18.06.2, but I've reproduced it with 18.06.4 and with the master branch from
> the GitHub repo.  Since the leak occurs as mesh links are created and
> destroyed, I was able to reproduce it with a simple two-node setup where I
> monitor the wpa_supplicant process VSZ on one node and repeatedly bring wifi
> up and down on the other node.
> 
> I've traced it back to the 18.06.2 release, specifically to lines 34-35 of
> package/network/services/hostapd/patches/015-mesh-do-not-use-offchan-mgmt-tx-on-DFS.patch
> +                 (modes = nl80211_get_hw_feature_data(bss, &num_modes,
> &flags, +
> &dfs_domain)) && That code was added in
> a35f24309021c1c0e9cbed0faedf58b941cb4bd3.
> 
> I removed the entire patch file to resolve the memory leak because the
> subsequent call to ieee80211_is_dfs() uses the return value from
> nl80211_get_hw_feature_data().  However, I know the problem is specifically
> related to the nl80211_get_hw_feature_data() call because I stepped-backward
> through commits of the hostapd source until I got back to
> 0f7fc6b98de9c69f511b9b22f2b65553126362eb, where ieee80211_is_dfs() had only
> one argument and didn't rely on the nl80211_get_hw_feature_data() return
> value.  At that point, the memory leak still occurred until I commented-out
> the call to nl80211_get_hw_feature_data().
> 
> I attempted to dive into nl80211_get_hw_feature_data(), but was quickly
> lost, so I defer to those that are more experienced in that code.

you did a nice job here to track it down, so thanks for reporting this, can
you try this patch[1]?

1. https://git.openwrt.org/c818ab2b8649accb3739b9234f2d07e16011fda6

-- ynezz

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