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Subject[ 61/69] xhci: Fix invalid loop check in xhci_free_tt_info()
3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@suse.de>

commit 46ed8f00d8982e49f8fe2c1a9cea192f640cb3ba upstream.

xhci_free_tt_info() may access the invalid memory when it removes the
last entry but the list is not empty. Then tt_next reaches to the
list head but it still tries to check the tt_info of that entry.

This patch fixes the bug and cleans up the messy code by rewriting
with a simple list_for_each_entry_safe().

This patch should be backported to kernels as old as 3.2, that contain
the commit 839c817ce67178ca3c7c7ad534c571bba1e69ebe "xhci: Store
information about roothubs and TTs."

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Reviewed-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/usb/host/xhci-mem.c | 39 ++++++++++-----------------------------
1 file changed, 10 insertions(+), 29 deletions(-)

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index ec4338e..898dfc8 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -793,10 +793,9 @@ static void xhci_free_tt_info(struct xhci_hcd *xhci,
struct xhci_virt_device *virt_dev,
int slot_id)
{
- struct list_head *tt;
struct list_head *tt_list_head;
- struct list_head *tt_next;
- struct xhci_tt_bw_info *tt_info;
+ struct xhci_tt_bw_info *tt_info, *next;
+ bool slot_found = false;

/* If the device never made it past the Set Address stage,
* it may not have the real_port set correctly.
@@ -808,34 +807,16 @@ static void xhci_free_tt_info(struct xhci_hcd *xhci,
}

tt_list_head = &(xhci->rh_bw[virt_dev->real_port - 1].tts);
- if (list_empty(tt_list_head))
- return;
-
- list_for_each(tt, tt_list_head) {
- tt_info = list_entry(tt, struct xhci_tt_bw_info, tt_list);
- if (tt_info->slot_id == slot_id)
+ list_for_each_entry_safe(tt_info, next, tt_list_head, tt_list) {
+ /* Multi-TT hubs will have more than one entry */
+ if (tt_info->slot_id == slot_id) {
+ slot_found = true;
+ list_del(&tt_info->tt_list);
+ kfree(tt_info);
+ } else if (slot_found) {
break;
+ }
}
- /* Cautionary measure in case the hub was disconnected before we
- * stored the TT information.
- */
- if (tt_info->slot_id != slot_id)
- return;
-
- tt_next = tt->next;
- tt_info = list_entry(tt, struct xhci_tt_bw_info,
- tt_list);
- /* Multi-TT hubs will have more than one entry */
- do {
- list_del(tt);
- kfree(tt_info);
- tt = tt_next;
- if (list_empty(tt_list_head))
- break;
- tt_next = tt->next;
- tt_info = list_entry(tt, struct xhci_tt_bw_info,
- tt_list);
- } while (tt_info->slot_id == slot_id);
}

int xhci_alloc_tt_info(struct xhci_hcd *xhci,



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