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cfg80211: don't "leak" uncompleted scans

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___cfg80211_scan_done() can be called in some cases
(e.g. on NETDEV_DOWN) before the low level driver
notified scan completion (which is indicated by
passing leak=true).

Clearing rdev->scan_req in this case is buggy, as
scan_done_wk might have already being queued/running
(and can't be flushed as it takes rtnl()).

If a new scan will be requested at this stage, the
scan_done_wk will try freeing it (instead of the
previous scan), and this will later result in
a use after free.

Simply remove the "leak" option, and replace it with
a standard WARN_ON.

An example backtrace after such crash:
Unable to handle kernel paging request at virtual address fffffee5
pgd = c0004000
[fffffee5] *pgd=9fdf6821, *pte=00000000, *ppte=00000000
Internal error: Oops: 17 [#1] SMP ARM
PC is at cfg80211_scan_done+0x28/0xc4 [cfg80211]
LR is at __ieee80211_scan_completed+0xe4/0x2dc [mac80211]
[<bf0077b0>] (cfg80211_scan_done+0x28/0xc4 [cfg80211])
[<bf0973d4>] (__ieee80211_scan_completed+0xe4/0x2dc [mac80211])
[<bf0982cc>] (ieee80211_scan_work+0x94/0x4f0 [mac80211])
[<c005fd10>] (process_one_work+0x1b0/0x4a8)
[<c0060404>] (worker_thread+0x138/0x37c)
[<c0066d70>] (kthread+0xa4/0xb0)

Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Eliad Peller 2013-12-05 18:30:17 +02:00 • committed by Johannes Berg
parent a2b70e833e
commit 4a58e7c384
3 changed files with 8 additions and 30 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

20
net/wireless/core.c
View file

@ -203,17 +203,8 @@ void cfg80211_stop_p2p_device(struct cfg80211_registered_device *rdev,
rdev->opencount--;
if (rdev->scan_req && rdev->scan_req->wdev == wdev) {
/*
* If the scan request wasn't notified as done, set it
* to aborted and leak it after a warning. The driver
* should have notified us that it ended at the latest
* during rdev_stop_p2p_device().
*/
if (WARN_ON(!rdev->scan_req->notified))
rdev->scan_req->aborted = true;
___cfg80211_scan_done(rdev, !rdev->scan_req->notified);
}
WARN_ON(rdev->scan_req && rdev->scan_req->wdev == wdev &&
!rdev->scan_req->notified);
}
static int cfg80211_rfkill_set_block(void *data, bool blocked)
@ -859,11 +850,8 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
break;
case NETDEV_DOWN:
cfg80211_update_iface_num(rdev, wdev->iftype, -1);
if (rdev->scan_req && rdev->scan_req->wdev == wdev) {
if (WARN_ON(!rdev->scan_req->notified))
rdev->scan_req->aborted = true;
___cfg80211_scan_done(rdev, true);
}
WARN_ON(rdev->scan_req && rdev->scan_req->wdev == wdev &&
!rdev->scan_req->notified);
if (WARN_ON(rdev->sched_scan_req &&
rdev->sched_scan_req->dev == wdev->netdev)) {

2
net/wireless/core.h
View file

@ -361,7 +361,7 @@ int cfg80211_validate_key_settings(struct cfg80211_registered_device *rdev,
struct key_params *params, int key_idx,
bool pairwise, const u8 *mac_addr);
void __cfg80211_scan_done(struct work_struct *wk);
void ___cfg80211_scan_done(struct cfg80211_registered_device *rdev, bool leak);
void ___cfg80211_scan_done(struct cfg80211_registered_device *rdev);
void __cfg80211_sched_scan_results(struct work_struct *wk);
int __cfg80211_stop_sched_scan(struct cfg80211_registered_device *rdev,
bool driver_initiated);

16
net/wireless/scan.c
View file

@ -161,7 +161,7 @@ static void __cfg80211_bss_expire(struct cfg80211_registered_device *dev,
dev->bss_generation++;
}
void ___cfg80211_scan_done(struct cfg80211_registered_device *rdev, bool leak)
void ___cfg80211_scan_done(struct cfg80211_registered_device *rdev)
{
struct cfg80211_scan_request *request;
struct wireless_dev *wdev;
@ -210,17 +210,7 @@ void ___cfg80211_scan_done(struct cfg80211_registered_device *rdev, bool leak)
dev_put(wdev->netdev);
rdev->scan_req = NULL;
/*
* OK. If this is invoked with "leak" then we can't
* free this ... but we've cleaned it up anyway. The
* driver failed to call the scan_done callback, so
* all bets are off, it might still be trying to use
* the scan request or not ... if it accesses the dev
* in there (it shouldn't anyway) then it may crash.
*/
if (!leak)
kfree(request);
kfree(request);
}
void __cfg80211_scan_done(struct work_struct *wk)
@ -231,7 +221,7 @@ void __cfg80211_scan_done(struct work_struct *wk)
scan_done_wk);
rtnl_lock();
___cfg80211_scan_done(rdev, false);
___cfg80211_scan_done(rdev);
rtnl_unlock();
}