lkml.org 
[lkml]   [2017]   [Nov]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] apparmor: initialized returned struct aa_perms
From
Date
On 11/20/2017 06:00 AM, Arnd Bergmann wrote:
> On Mon, Sep 25, 2017 at 4:29 PM, John Johansen
> <john.johansen@canonical.com> wrote:
>> On 09/15/2017 03:55 PM, Arnd Bergmann wrote:
>>> gcc-4.4 points out suspicious code in compute_mnt_perms, where
>>> the aa_perms structure is only partially initialized before getting
>>> returned:
>>>
>>> security/apparmor/mount.c: In function 'compute_mnt_perms':
>>> security/apparmor/mount.c:227: error: 'perms.prompt' is used uninitialized in this function
>>> security/apparmor/mount.c:227: error: 'perms.hide' is used uninitialized in this function
>>> security/apparmor/mount.c:227: error: 'perms.cond' is used uninitialized in this function
>>> security/apparmor/mount.c:227: error: 'perms.complain' is used uninitialized in this function
>>> security/apparmor/mount.c:227: error: 'perms.stop' is used uninitialized in this function
>>> security/apparmor/mount.c:227: error: 'perms.deny' is used uninitialized in this function
>>>
>>> Returning or assigning partially initialized structures is a bit tricky,
>>> in particular it is explicitly allowed in c99 to assign a partially
>>> intialized structure to another, as long as only members are read that
>>> have been initialized earlier. Looking at what various compilers do here,
>>> the version that produced the warning copied unintialized stack data,
>>> while newer versions (and also clang) either set the other members to
>>> zero or don't update the parts of the return buffer that are not modified
>>> in the temporary structure, but they never warn about this.
>>>
>>> In case of apparmor, it seems better to be a little safer and always
>>> initialize the aa_perms structure. Most users already do that, this
>>> changes the remaining ones, including the one instance that I got the
>>> warning for.
>>>
>>> Fixes: fa488437d0f9 ("apparmor: add mount mediation")
>>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>>
>> I've pulled this into apparmor-next
>
> It apparently never made it into mainline. What happened?
>
> Arnd
>
Its in apparmor-next and is going with today's pull request

\
 
 \ /
  Last update: 2017-11-20 16:48    [W:0.048 / U:9.828 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site