linux-kernel - [ 06/38] firewire: cdev: fix 32 bit userland on 64 bit kernel compat corner cases

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Date:	Fri, 16 Mar 2012 16:34:53 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Carl Karsten <carl@...sonnelware.com>,
	Clemens Ladisch <clemens@...isch.de>,
	Stefan Richter <stefanr@...6.in-berlin.de>
Subject: [ 06/38] firewire: cdev: fix 32 bit userland on 64 bit kernel compat corner cases

3.0-stable review patch.  If anyone has any objections, please let me know.

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

From: Stefan Richter <stefanr@...6.in-berlin.de>

commit 9c1176b6a28850703ea6e3a0f0c703f6d6c61cd3 upstream.

Clemens points out that we need to use compat_ptr() in order to safely
cast from u64 to addresses of a 32-bit usermode client.

Before, our conversion went wrong
  - in practice if the client cast from pointer to integer such that
    sign-extension happened, (libraw1394 and libdc1394 at least were not
    doing that, IOW were not affected)
or
  - in theory on s390 (which doesn't have FireWire though) and on the
    tile architecture, regardless of what the client does.
The bug would usually be observed as the initial get_info ioctl failing
with "Bad address" (EFAULT).

Reported-by: Carl Karsten <carl@...sonnelware.com>
Reported-by: Clemens Ladisch <clemens@...isch.de>
Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/firewire/core-cdev.c |   24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -216,15 +216,33 @@ struct inbound_phy_packet_event {
 	struct fw_cdev_event_phy_packet phy_packet;
 };
 
-static inline void __user *u64_to_uptr(__u64 value)
+#ifdef CONFIG_COMPAT
+static void __user *u64_to_uptr(u64 value)
+{
+	if (is_compat_task())
+		return compat_ptr(value);
+	else
+		return (void __user *)(unsigned long)value;
+}
+
+static u64 uptr_to_u64(void __user *ptr)
+{
+	if (is_compat_task())
+		return ptr_to_compat(ptr);
+	else
+		return (u64)(unsigned long)ptr;
+}
+#else
+static inline void __user *u64_to_uptr(u64 value)
 {
 	return (void __user *)(unsigned long)value;
 }
 
-static inline __u64 uptr_to_u64(void __user *ptr)
+static inline u64 uptr_to_u64(void __user *ptr)
 {
-	return (__u64)(unsigned long)ptr;
+	return (u64)(unsigned long)ptr;
 }
+#endif /* CONFIG_COMPAT */
 
 static int fw_device_op_open(struct inode *inode, struct file *file)
 {


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