New subject: linux-5.7-rc1/tools/testing/selftests/resctrl/cqm_test.c:89:15: error: Buffer is accessed out of bounds

13 Apr 2020


      +Sai
On 4/13/2020 2:43 AM, David Binderman wrote:
...
Hello there,
Source code is
while (fgets(temp, 1024, fp)) {
but
char *token_array[8], temp[512];


Use of compiler flag -D_FORTIFY_SOURCE=2 would have found the problem.
For example:
# include <stdio.h>
extern void g( int);
void
f( FILE * fp)
{
   char buf[ 100];
while (fgets( buf, 200, fp) != 0)
   {
   	g( 1);
   }
}
gives
$ /home/dcb/gcc/results/bin/gcc -c -g -O2 -D_FORTIFY_SOURCE=2 apr13c.cc
In file included from /usr/include/stdio.h:867,
                 from apr13c.cc:2:
In function ‘char* fgets(char*, int, FILE*)’,
    inlined from ‘void f(FILE*)’ at apr13c.cc:11:14:
/usr/include/bits/stdio2.h:263:26: warning: call to ‘__fgets_chk_warn’ declared with attribute warning: fgets called with bigger size than length of destination buffer [-Wattribute-warning]
I suggest switch on compiler flag -D_FORTIFY_SOURCE=2 in
all development builds.
Thank you very much for catching this David.
Sai: could you include this fix in your upcoming series of fixes? Using
the pattern of "fgets(buf, sizeof(buf), ...)" instead of hard coding the
size should be helpful here.
Reinette

Re: linux-5.7-rc1/tools/testing/selftests/resctrl/cqm_test.c:89:15: error: Buffer is accessed out of bounds