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Date: Mon, 8 Apr 2013 22:18:30 +0530 (IST)
From: P J P <ppandit@...hat.com>
To: Dan Carpenter <dan.carpenter@...cle.com>
cc: oss security list <oss-security@...ts.openwall.com>
Subject: Re: CVE Request: kernel information leak in
fs/compat_ioctl.c VIDEO_SET_SPU_PALETTE
Hello Dan,
+-- On Mon, 8 Apr 2013, Dan Carpenter wrote --+
| The x86 version is ok but asm-generic version of get_user() doesn't clear x.
|
| include/asm-generic/uaccess.h
|
| 226 #define get_user(x, ptr) \
| 227 ({ \
| 228 might_sleep(); \
| 229 access_ok(VERIFY_READ, ptr, sizeof(*ptr)) ? \
| 230 __get_user(x, ptr) : \
| 231 -EFAULT; \
| 232 })
Here, following call sequence ensures that 'x' is always initialised with
user memory contents.
get_user
-> __get_user
-> __get_user_fn
-> __copy_from_user
Unless `access_ok()' in `__get_user' returns 0, which it does not, OR
sizeof(*ptr) is > 8 bytes.
Thank you.
--
Prasad J Pandit / Red Hat Security Response Team
DB7A 84C5 D3F9 7CD1 B5EB C939 D048 7860 3655 602B
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