linux-kernel - Re: Security: Replace dac_mmap_min_addr to mmap_min_addr in cap_file

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Date:	Wed, 14 Apr 2010 13:50:40 +0800
From:	wzt wzt <wzt.wzt@...il.com>
To:	Eric Paris <eparis@...isplace.org>
Cc:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, jmorris@...ei.org
Subject: Re: Security: Replace dac_mmap_min_addr to mmap_min_addr in 
	cap_file_mmap()

still not understand,  if CONFIG_LSM_MMAP_MIN_ADDR is not set,
mmap_min_addr is equal dac_mmap_min_addr, right?
if not, mmap_min_addr is set as CONFIG_LSM_MMAP_MIN_ADDR.  what's the
effect of mmap_min_addr?  except round_hint_to_min() will use
mmap_min_addr, any other functions will call it?
Anyway, the comments need change mmap_min_addr as dac_mmap_min_addr,
right? If i'm wrong, please point it, thanks.
/*
 * If the process is attempting to map memory below mmap_min_addr they need   |{
 * CAP_SYS_RAWIO.
 */

On Wed, Apr 14, 2010 at 11:02 AM, Eric Paris <eparis@...isplace.org> wrote:
> NAK NAK NAK
>
> go back and reread the whole purpose for the separation.
>
> -Eric
>
> On Tue, Apr 13, 2010 at 10:48 PM,  <wzt.wzt@...il.com> wrote:
>> cap_file_mmap() comments said "If the process is attempting to map
>> memory below mmap_min_addr", if CONFIG_LSM_MMAP_MIN_ADDR is set,
>> dac_mmap_min_addr is not equal mmap_min_addr, so replace dac_mmap_min_addr
>> to mmap_min_addr seems to be better.
>>
>> Signed-off-by: Zhitong Wang <zhitong.wangzt@...baba-inc.com>
>>
>> ---
>>  include/linux/security.h |    1 +
>>  security/commoncap.c     |    2 +-
>>  2 files changed, 2 insertions(+), 1 deletions(-)
>>
>> diff --git a/include/linux/security.h b/include/linux/security.h
>> index 233d20b..61fd9e7 100644
>> --- a/include/linux/security.h
>> +++ b/include/linux/security.h
>> @@ -101,6 +101,7 @@ void reset_security_ops(void);
>>  extern unsigned long mmap_min_addr;
>>  extern unsigned long dac_mmap_min_addr;
>>  #else
>> +#define mmap_min_addr          0UL
>>  #define dac_mmap_min_addr      0UL
>>  #endif
>>
>> diff --git a/security/commoncap.c b/security/commoncap.c
>> index 6166973..878cf89 100644
>> --- a/security/commoncap.c
>> +++ b/security/commoncap.c
>> @@ -942,7 +942,7 @@ int cap_file_mmap(struct file *file, unsigned long reqprot,
>>  {
>>        int ret = 0;
>>
>> -       if (addr < dac_mmap_min_addr) {
>> +       if (addr < mmap_min_addr) {
>>                ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO,
>>                                  SECURITY_CAP_AUDIT);
>>                /* set PF_SUPERPRIV if it turns out we allow the low mmap */
>> --
>> 1.6.5.3
>>
>> --
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>
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