Messages in this thread |  | | Subject | Re: [PATCH] cw1200: Revert unnecessary patches that fix unreal use-after-free bugs | From | Jia-Ju Bai <> | Date | Mon, 24 May 2021 09:36:06 +0800 |
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Thanks for fixing my previous mistake. The patch looks good.
On 2021/5/22 6:32, Hang Zhang wrote: > A previous commit 4f68ef64cd7f ("cw1200: Fix concurrency > use-after-free bugs in cw1200_hw_scan()") tried to fix a seemingly > use-after-free bug between cw1200_bss_info_changed() and > cw1200_hw_scan(), where the former frees a sk_buff pointed > to by frame.skb, and the latter accesses the sk_buff > pointed to by frame.skb. However, this issue should be a > false alarm because: > > (1) "frame.skb" is not a shared variable between the above > two functions, because "frame" is a local function variable, > each of the two functions has its own local "frame" - they > just happen to have the same variable name. > > (2) the sk_buff(s) pointed to by these two "frame.skb" are > also two different object instances, they are individually > allocated by different dev_alloc_skb() within the two above > functions. To free one object instance will not invalidate > the access of another different one. > > Based on these facts, the previous commit should be unnecessary. > Moreover, it also introduced a missing unlock which was > addressed in a subsequent commit 51c8d24101c7 ("cw1200: fix missing > unlock on error in cw1200_hw_scan()"). Now that the > original use-after-free is unreal, these two commits should > be reverted. This patch performs the reversion. > > Fixes: 4f68ef64cd7f ("cw1200: Fix concurrency use-after-free bugs in cw1200_hw_scan()") > Fixes: 51c8d24101c7 ("cw1200: fix missing unlock on error in cw1200_hw_scan()") > Signed-off-by: Hang Zhang <zh.nvgt@gmail.com> > --- > drivers/net/wireless/st/cw1200/scan.c | 17 +++++++---------- > 1 file changed, 7 insertions(+), 10 deletions(-) > > diff --git a/drivers/net/wireless/st/cw1200/scan.c b/drivers/net/wireless/st/cw1200/scan.c > index 988581cc134b..1f856fbbc0ea 100644 > --- a/drivers/net/wireless/st/cw1200/scan.c > +++ b/drivers/net/wireless/st/cw1200/scan.c > @@ -75,30 +75,27 @@ int cw1200_hw_scan(struct ieee80211_hw *hw, > if (req->n_ssids > WSM_SCAN_MAX_NUM_OF_SSIDS) > return -EINVAL; > > - /* will be unlocked in cw1200_scan_work() */ > - down(&priv->scan.lock); > - mutex_lock(&priv->conf_mutex); > - > frame.skb = ieee80211_probereq_get(hw, priv->vif->addr, NULL, 0, > req->ie_len); > - if (!frame.skb) { > - mutex_unlock(&priv->conf_mutex); > - up(&priv->scan.lock); > + if (!frame.skb) > return -ENOMEM; > - } > > if (req->ie_len) > skb_put_data(frame.skb, req->ie, req->ie_len); > > + /* will be unlocked in cw1200_scan_work() */ > + down(&priv->scan.lock); > + mutex_lock(&priv->conf_mutex); > + > ret = wsm_set_template_frame(priv, &frame); > if (!ret) { > /* Host want to be the probe responder. */ > ret = wsm_set_probe_responder(priv, true); > } > if (ret) { > - dev_kfree_skb(frame.skb); > mutex_unlock(&priv->conf_mutex); > up(&priv->scan.lock); > + dev_kfree_skb(frame.skb); > return ret; > } > > @@ -120,8 +117,8 @@ int cw1200_hw_scan(struct ieee80211_hw *hw, > ++priv->scan.n_ssids; > } > > - dev_kfree_skb(frame.skb); > mutex_unlock(&priv->conf_mutex); > + dev_kfree_skb(frame.skb); > queue_work(priv->workqueue, &priv->scan.work); > return 0; > }
Acked-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Best wishes, Jia-Ju Bai
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