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isdn: Disable IIOCDBGVAR

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It was possible to directly leak the kernel address where the isdn_dev
structure pointer was stored. This is a kernel ASLR bypass for anyone
with access to the ioctl. The code had been present since the beginning
of git history, though this shouldn't ever be needed for normal operation,
therefore remove it.

Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Karsten Keil <isdn@linux-pingi.de>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Kees Cook 2018-08-15 12:14:05 -07:00 committed by David S. Miller
parent 4531681837
commit 5e22002aa8
1 changed files with 1 additions and 7 deletions
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8
drivers/isdn/i4l/isdn_common.c
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@ -1640,13 +1640,7 @@ isdn_ioctl(struct file *file, uint cmd, ulong arg)
} else
return -EINVAL;
case IIOCDBGVAR:
if (arg) {
if (copy_to_user(argp, &dev, sizeof(ulong)))
return -EFAULT;
return 0;
} else
return -EINVAL;
break;
return -EINVAL;
default:
if ((cmd & IIOCDRVCTL) == IIOCDRVCTL)
cmd = ((cmd >> _IOC_NRSHIFT) & _IOC_NRMASK) & ISDN_DRVIOCTL_MASK;