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USB: EHCI: fix NULL pointer dererence in HCDs that use HCD_LOCAL_MEM

PATCH In review Andrea Righi 2 participants 2 messages Jun 28, 2010

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USB USB ehci driver
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Andrea Righi

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#0 lore raw

PATCH 1/1 USB: EHCI: fix NULL pointer dererence in HCDs that use HCD_LOCAL_MEM

If we use the HCD_LOCAL_MEM flag and dma_declare_coherent_memory() to enforce the host controller's local memory utilization we also need to disable native scatter-gather support, otherwise hcd_alloc_coherent() in map_urb_for_dma() is called with urb->transfer_buffer == NULL, that triggers a NULL pointer dereference.

We can also consider to add a WARN_ON() and return an error code to better catch this problem in the future.

Signed-off-by Andrea Righi <[email protected]>
---
 drivers/usb/core/hcd.c      |    5 +++++
 drivers/usb/host/ehci-hcd.c |    3 ++-
 2 files changed, 7 insertions(+), 1 deletions(-)
drivers/usb/core/hcd.c +5 -0
index 12742f1..161c757 100644
@@ -1219,6 +1219,11 @@ static int hcd_alloc_coherent(struct usb_bus *bus,
 {
 	unsigned char *vaddr;
 
+	if (*vaddr_handle == NULL) {
+		WARN_ON_ONCE(1);
+		return -EFAULT;
+	}
+
 	vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr),
 				 mem_flags, dma_handle);
 	if (!vaddr)
drivers/usb/host/ehci-hcd.c +2 -1
index a3ef2a9..27e0351 100644
@@ -606,7 +606,8 @@ static int ehci_init(struct usb_hcd *hcd)
 	ehci->command = temp;
 
 	/* Accept arbitrarily long scatter-gather lists */
-	hcd->self.sg_tablesize = ~0;
+	if (!(hcd->driver->flags & HCD_LOCAL_MEM))
+		hcd->self.sg_tablesize = ~0;
 	return 0;
 }
maintainer
#1 lore raw
Quoted 36 lines · Andrea Righi

If we use the HCD_LOCAL_MEM flag and dma_declare_coherent_memory() to enforce the host controller's local memory utilization we also need to disable native scatter-gather support, otherwise hcd_alloc_coherent() in map_urb_for_dma() is called with urb->transfer_buffer == NULL, that triggers a NULL pointer dereference.

We can also consider to add a WARN_ON() and return an error code to better catch this problem in the future.

Signed-off-by Andrea Righi <[email protected]>
---
 drivers/usb/core/hcd.c      |    5 +++++
 drivers/usb/host/ehci-hcd.c |    3 ++-
 2 files changed, 7 insertions(+), 1 deletions(-)
drivers/usb/core/hcd.c +5 -0
index 12742f1..161c757 100644
@@ -1219,6 +1219,11 @@ static int hcd_alloc_coherent(struct usb_bus *bus,
 {
 	unsigned char *vaddr;
 
+	if (*vaddr_handle == NULL) {
+		WARN_ON_ONCE(1);
+		return -EFAULT;
+	}
+
 	vaddr = hcd_buffer_alloc(bus, size + sizeof(vaddr),
 				 mem_flags, dma_handle);
 	if (!vaddr)
drivers/usb/host/ehci-hcd.c +0 -0
index a3ef2a9..27e0351 100644

drivers/usb/host/ehci-hcd.c static int ehci_init(struct usb_hcd *hcd) · line 612

Quoted 8 lines
drivers/usb/host/ehci-hcd.c +2 -1
@@ -606,7 +606,8 @@ static int ehci_init(struct usb_hcd *hcd)
 	ehci->command = temp;
 
 	/* Accept arbitrarily long scatter-gather lists */
-	hcd->self.sg_tablesize = ~0;
+	if (!(hcd->driver->flags & HCD_LOCAL_MEM))
+		hcd->self.sg_tablesize = ~0;
 	return 0;
 }

Looks okay to me. You can add my Acked-by: when you submit this to Greg KH.

Alan Stern