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authorShigeru Yoshida <shigeru.yoshida@windriver.com>2018-02-02 13:51:39 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-02-28 10:19:41 +0100
commit85c3d26bd754160f6be90d8b078d70a1b35820e7 (patch)
tree5f506a4891c5b3b4b5c0a411418fefd8e78bcc05
parent50f80b646a2b76bde046ef180e2c5bfaef861510 (diff)
ohci-hcd: Fix race condition caused by ohci_urb_enqueue() and io_watchdog_func()
commit b2685bdacdaab065c172b97b55ab46c6be77a037 upstream. Running io_watchdog_func() while ohci_urb_enqueue() is running can cause a race condition where ohci->prev_frame_no is corrupted and the watchdog can mis-detect following error: ohci-platform 664a0800.usb: frame counter not updating; disabled ohci-platform 664a0800.usb: HC died; cleaning up Specifically, following scenario causes a race condition: 1. ohci_urb_enqueue() calls spin_lock_irqsave(&ohci->lock, flags) and enters the critical section 2. ohci_urb_enqueue() calls timer_pending(&ohci->io_watchdog) and it returns false 3. ohci_urb_enqueue() sets ohci->prev_frame_no to a frame number read by ohci_frame_no(ohci) 4. ohci_urb_enqueue() schedules io_watchdog_func() with mod_timer() 5. ohci_urb_enqueue() calls spin_unlock_irqrestore(&ohci->lock, flags) and exits the critical section 6. Later, ohci_urb_enqueue() is called 7. ohci_urb_enqueue() calls spin_lock_irqsave(&ohci->lock, flags) and enters the critical section 8. The timer scheduled on step 4 expires and io_watchdog_func() runs 9. io_watchdog_func() calls spin_lock_irqsave(&ohci->lock, flags) and waits on it because ohci_urb_enqueue() is already in the critical section on step 7 10. ohci_urb_enqueue() calls timer_pending(&ohci->io_watchdog) and it returns false 11. ohci_urb_enqueue() sets ohci->prev_frame_no to new frame number read by ohci_frame_no(ohci) because the frame number proceeded between step 3 and 6 12. ohci_urb_enqueue() schedules io_watchdog_func() with mod_timer() 13. ohci_urb_enqueue() calls spin_unlock_irqrestore(&ohci->lock, flags) and exits the critical section, then wake up io_watchdog_func() which is waiting on step 9 14. io_watchdog_func() enters the critical section 15. io_watchdog_func() calls ohci_frame_no(ohci) and set frame_no variable to the frame number 16. io_watchdog_func() compares frame_no and ohci->prev_frame_no On step 16, because this calling of io_watchdog_func() is scheduled on step 4, the frame number set in ohci->prev_frame_no is expected to the number set on step 3. However, ohci->prev_frame_no is overwritten on step 11. Because step 16 is executed soon after step 11, the frame number might not proceed, so ohci->prev_frame_no must equals to frame_no. To address above scenario, this patch introduces a special sentinel value IO_WATCHDOG_OFF and set this value to ohci->prev_frame_no when the watchdog is not pending or running. When ohci_urb_enqueue() schedules the watchdog (step 4 and 12 above), it compares ohci->prev_frame_no to IO_WATCHDOG_OFF so that ohci->prev_frame_no is not overwritten while io_watchdog_func() is running. Signed-off-by: Shigeru Yoshida <Shigeru.Yoshida@windriver.com> Signed-off-by: Haiqing Bai <Haiqing.Bai@windriver.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/usb/host/ohci-hcd.c10
-rw-r--r--drivers/usb/host/ohci-hub.c4
2 files changed, 10 insertions, 4 deletions
diff --git a/drivers/usb/host/ohci-hcd.c b/drivers/usb/host/ohci-hcd.c
index 44924824fa41..1099465b27f0 100644
--- a/drivers/usb/host/ohci-hcd.c
+++ b/drivers/usb/host/ohci-hcd.c
@@ -73,6 +73,7 @@ static const char hcd_name [] = "ohci_hcd";
#define STATECHANGE_DELAY msecs_to_jiffies(300)
#define IO_WATCHDOG_DELAY msecs_to_jiffies(275)
+#define IO_WATCHDOG_OFF 0xffffff00
#include "ohci.h"
#include "pci-quirks.h"
@@ -230,7 +231,7 @@ static int ohci_urb_enqueue (
}
/* Start up the I/O watchdog timer, if it's not running */
- if (!timer_pending(&ohci->io_watchdog) &&
+ if (ohci->prev_frame_no == IO_WATCHDOG_OFF &&
list_empty(&ohci->eds_in_use) &&
!(ohci->flags & OHCI_QUIRK_QEMU)) {
ohci->prev_frame_no = ohci_frame_no(ohci);
@@ -501,6 +502,7 @@ static int ohci_init (struct ohci_hcd *ohci)
setup_timer(&ohci->io_watchdog, io_watchdog_func,
(unsigned long) ohci);
+ ohci->prev_frame_no = IO_WATCHDOG_OFF;
ohci->hcca = dma_alloc_coherent (hcd->self.controller,
sizeof(*ohci->hcca), &ohci->hcca_dma, GFP_KERNEL);
@@ -730,7 +732,7 @@ static void io_watchdog_func(unsigned long _ohci)
u32 head;
struct ed *ed;
struct td *td, *td_start, *td_next;
- unsigned frame_no;
+ unsigned frame_no, prev_frame_no = IO_WATCHDOG_OFF;
unsigned long flags;
spin_lock_irqsave(&ohci->lock, flags);
@@ -835,7 +837,7 @@ static void io_watchdog_func(unsigned long _ohci)
}
}
if (!list_empty(&ohci->eds_in_use)) {
- ohci->prev_frame_no = frame_no;
+ prev_frame_no = frame_no;
ohci->prev_wdh_cnt = ohci->wdh_cnt;
ohci->prev_donehead = ohci_readl(ohci,
&ohci->regs->donehead);
@@ -845,6 +847,7 @@ static void io_watchdog_func(unsigned long _ohci)
}
done:
+ ohci->prev_frame_no = prev_frame_no;
spin_unlock_irqrestore(&ohci->lock, flags);
}
@@ -973,6 +976,7 @@ static void ohci_stop (struct usb_hcd *hcd)
if (quirk_nec(ohci))
flush_work(&ohci->nec_work);
del_timer_sync(&ohci->io_watchdog);
+ ohci->prev_frame_no = IO_WATCHDOG_OFF;
ohci_writel (ohci, OHCI_INTR_MIE, &ohci->regs->intrdisable);
ohci_usb_reset(ohci);
diff --git a/drivers/usb/host/ohci-hub.c b/drivers/usb/host/ohci-hub.c
index 248eb7702463..aca57bcb9afe 100644
--- a/drivers/usb/host/ohci-hub.c
+++ b/drivers/usb/host/ohci-hub.c
@@ -310,8 +310,10 @@ static int ohci_bus_suspend (struct usb_hcd *hcd)
rc = ohci_rh_suspend (ohci, 0);
spin_unlock_irq (&ohci->lock);
- if (rc == 0)
+ if (rc == 0) {
del_timer_sync(&ohci->io_watchdog);
+ ohci->prev_frame_no = IO_WATCHDOG_OFF;
+ }
return rc;
}