Commit 77c1ff39 authored Feb 11, 2010 by Andy Getzendanner Committed by Dave Airlie Feb 11, 2010

vgaarb: fix incorrect dereference of userspace pointer.



This patch corrects a userspace pointer dereference in the VGA arbiter
in 2.6.32.1.

copy_from_user() is used at line 822 to copy the contents of buf into
kbuf, but a call to strncmp() on line 964 uses buf rather than kbuf.  This
problem led to a GPF in strncmp() when X was started on my x86_32 systems.
 X triggered the behavior with a write of "target PCI:0000:01:00.0" to
/dev/vga_arbiter.

The patch has been tested against 2.6.32.1 and observed to correct the GPF
observed when starting X or manually writing the string "target
PCI:0000:01:00.0" to /dev/vga_arbiter.

Signed-off-by: Andy Getzendanner <james.getzendanner@students.olin.edu>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

parent 0a4583eb

drivers/gpu/vga/vgaarb.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -961,7 +961,7 @@ static ssize_t vga_arb_write(struct file file, const char __user buf,
		remaining -= 7;
		pr_devel("client 0x%p called 'target'\n", priv);
		/* if target is default */
		if (!strncmp(buf, "default", 7))
		if (!strncmp(kbuf, "default", 7))
		pdev = pci_dev_get(vga_default_device());
		else {
		if (!vga_pci_str_to_vars(curr_pos, remaining,

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