From: Hang Zhang zh.nvgt@gmail.com
stable inclusion from stable-5.10.50 commit a54e9166e7881e849d0bbf4ce533742b8c5c86ab bugzilla: 174522 https://gitee.com/openeuler/kernel/issues/I4DNFY
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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[ Upstream commit 3f60f4685699aa6006e58e424637e8e413e0a94d ]
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 Signed-off-by: Kalle Valo kvalo@codeaurora.org Link: https://lore.kernel.org/r/20210521223238.25020-1-zh.nvgt@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Chen Jun chenjun102@huawei.com Acked-by: Weilong Chen chenweilong@huawei.com Signed-off-by: Chen Jun chenjun102@huawei.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; }