Re: [PATCH] 4.9.13 brcmfmac: fix use-after-free on resume

On 6-3-2017 15:50, Daniel J Blueman wrote:

On 6 March 2017 at 21:00, Arend Van Spriel [off-list ref] wrote:

quoted

+ linux-wireless

On 6-3-2017 8:14, Daniel J Blueman wrote:

quoted

KASAN reported 'struct wireless_dev wdev' was read after being freed.
Fix by freeing after the access.

I would rather like to see the KASAN report, because something is off
here. This function is called with wdev as a parameter so how can it be
accessed after free here? brcmf_remove_interface() does not free the
wdev nor the brcmf_cfg80211_vif instance which contains the wdev.

Regards,
Arend

quoted

Signed-off-by: Daniel J Blueman <redacted>

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c

b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
index de19c7c..aa0f470 100644

--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/p2p.c

@@ -2288,12 +2288,13 @@ int brcmf_p2p_del_vif(struct wiphy *wiphy,

struct wireless_dev *wdev)
                else
                        err = 0;
        }
-       brcmf_remove_interface(vif->ifp, true);

-       brcmf_cfg80211_arm_vif_event(cfg, NULL);
        if (vif->wdev.iftype != NL80211_IFTYPE_P2P_DEVICE)
                p2p->bss_idx[P2PAPI_BSSCFG_CONNECTION].vif = NULL;

+       brcmf_remove_interface(vif->ifp, true);
+       brcmf_cfg80211_arm_vif_event(cfg, NULL);
+
        return err;
 }

Sure, https://quora.org/kernel/brcmfmac/dmesg.txt

So this dmesg looks to be about a separate issue during resume, which
you sent an email about earlier [1] which is about using wiphy struct
after free. However, back to this I further checked the code and it
seems the vif is indeed freed through the netdev destructor callback
upon calling brcmf_remove_inteface(). However, I would prefer to store
vif->wdev.iftype in a local variable and avoid changing the order of the
calls in the code.

Regards,
Arend

[1] http://marc.info/?l=linux-netdev&m=148878437808750&w=2

vmlinux, cfg80211.o, brcmfmac.o and config are in the same path; this
is against v4.9.13 stock.