| Message ID | 20210521223238.25020-1-zh.nvgt@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | cw1200: Revert unnecessary patches that fix unreal use-after-free bugs | expand |
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
Hang Zhang <zh.nvgt@gmail.com> 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> > Acked-by: Jia-Ju Bai <baijiaju1990@gmail.com> Patch applied to wireless-drivers-next.git, thanks. 3f60f4685699 cw1200: Revert unnecessary patches that fix unreal use-after-free bugs -- https://patchwork.kernel.org/project/linux-wireless/patch/20210521223238.25020-1-zh.nvgt@gmail.com/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
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; }
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(-)