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Subject[PATCH] [222/223] Fix pktcdvd ioctl dev_minor range check
2.6.35-longterm review patch.  If anyone has any objections, please let me know.

From: Dan Rosenberg <>

Upstream 252a52aa4fa22a668f019e55b3aac3ff71ec1c29

The PKT_CTRL_CMD_STATUS device ioctl retrieves a pointer to a
pktcdvd_device from the global pkt_devs array. The index into this
array is provided directly by the user and is a signed integer, so the
comparison to ensure that it falls within the bounds of this array will
fail when provided with a negative index.

This can be used to read arbitrary kernel memory or cause a crash due to
an invalid pointer dereference. This can be exploited by users with
permission to open /dev/pktcdvd/control (on many distributions, this is
readable by group "cdrom").

Signed-off-by: Dan Rosenberg <>
[ Rather than add a cast, just make the function take the right type -Linus ]
Signed-off-by: Linus Torvalds <>
Signed-off-by: Andi Kleen <>
drivers/block/pktcdvd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux/drivers/block/pktcdvd.c
--- linux.orig/drivers/block/pktcdvd.c
+++ linux/drivers/block/pktcdvd.c
@@ -2368,7 +2368,7 @@ static void pkt_release_dev(struct pktcd

-static struct pktcdvd_device *pkt_find_dev_from_minor(int dev_minor)
+static struct pktcdvd_device *pkt_find_dev_from_minor(unsigned int dev_minor)
if (dev_minor >= MAX_WRITERS)
return NULL;

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