[PATCH] tty/vt: set_get_cmap() check user buffer

[Michael Gehring]

set_get_cmap() ignores the result of {get,put}_user(), causing ioctl(vt,
{G,P}IO_CMAP, 0xdeadbeef) to silently fail.

Another side effect of this: calling the PIO_CMAP ioctl with an invalid
buffer will zero the default colormap and the palette for all vts (all
colors set to black).

Use access_ok() and return -EFAULT when appropriate.

Signed-off-by: Michael Gehring <mg@xxxxxxxx>
---
 drivers/tty/vt/vt.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index e716839..176b2a1 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -3897,15 +3897,18 @@ static int set_get_cmap(unsigned char __user *arg, int set)
 
     WARN_CONSOLE_UNLOCKED();
 
+    if (!access_ok(set ? VERIFY_READ : VERIFY_WRITE, arg, 3 * 16))
+	return -EFAULT;
+
     for (i = 0; i < 16; i++)
 	if (set) {
-	    get_user(default_red[i], arg++);
-	    get_user(default_grn[i], arg++);
-	    get_user(default_blu[i], arg++);
+	    __get_user(default_red[i], arg++);
+	    __get_user(default_grn[i], arg++);
+	    __get_user(default_blu[i], arg++);
 	} else {
-	    put_user(default_red[i], arg++);
-	    put_user(default_grn[i], arg++);
-	    put_user(default_blu[i], arg++);
+	    __put_user(default_red[i], arg++);
+	    __put_user(default_grn[i], arg++);
+	    __put_user(default_blu[i], arg++);
 	}
     if (set) {
 	for (i = 0; i < MAX_NR_CONSOLES; i++)
-- 
1.7.9.4

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