lkml.org 
[lkml]   [2019]   [May]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] tipc: Avoid copying bytes beyond the supplied data
On Sun, May 05, 2019 at 08:20:14PM +0000, Chris Packham wrote:
> On 4/05/19 4:45 PM, David Miller wrote:
> > From: Chris Packham <chris.packham@alliedtelesis.co.nz>
> > Date: Thu, 2 May 2019 15:10:04 +1200
> >
> >> TLV_SET is called with a data pointer and a len parameter that tells us
> >> how many bytes are pointed to by data. When invoking memcpy() we need
> >> to careful to only copy len bytes.
> >>
> >> Previously we would copy TLV_LENGTH(len) bytes which would copy an extra
> >> 4 bytes past the end of the data pointer which newer GCC versions
> >> complain about.
> >>
> >> In file included from test.c:17:
> >> In function 'TLV_SET',
> >> inlined from 'test' at test.c:186:5:
> >> /usr/include/linux/tipc_config.h:317:3:
> >> warning: 'memcpy' forming offset [33, 36] is out of the bounds [0, 32]
> >> of object 'bearer_name' with type 'char[32]' [-Warray-bounds]
> >> memcpy(TLV_DATA(tlv_ptr), data, tlv_len);
> >> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >> test.c: In function 'test':
> >> test.c::161:10: note:
> >> 'bearer_name' declared here
> >> char bearer_name[TIPC_MAX_BEARER_NAME];
> >> ^~~~~~~~~~~
> >>
> >> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
> >
> > But now the pad bytes at the end are uninitialized.
> >
> > The whole idea is that the encapsulating TLV object has to be rounded
> > up in size based upon the given 'len' for the data.
> >
>
> TLV_LENGTH() does not account for any padding bytes due to the
> alignment. TLV_SPACE() does but that wasn't used in the code before my
> change.
>
> Are you suggesting something like this
>
>
> - if (len && data)
> - memcpy(TLV_DATA(tlv_ptr), data, tlv_len);
> + if (len && data) {
> + memcpy(TLV_DATA(tlv_ptr), data, len);
> + memset(TLV_DATA(tlv_ptr) + len, 0, TLV_SPACE(len) -
> TLV_LENGTH(len));
> + }
>
>

For zeroing out the padding, should that be done in TCM_SET in the same
file as well? That one only copies data_len bytes but doesn't zero out
any alignment padding.

\
 
 \ /
  Last update: 2019-05-05 22:57    [W:0.121 / U:0.332 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site