Bug 1080421

Description of problem:
I recompiled the kernel without NUMA support (while trying to debug another NUMA issue) and ran 'numactl --hardware' and it crashed with a seg fault.

The problem is that /sys/devices/system/node does not exist on non-NUMA systems, but numactl ignoes the ENOENT error it receives when trying to access this path.

The bug lies in the read_distance_table() function just above in distance.c:52

In particular, this loop:

 61     for (nd = 0;; nd++) { 
 62         char fn[100];
 63         FILE *dfh;
 64         sprintf(fn, "/sys/devices/system/node/node%d/distance", nd);
 65         dfh = fopen(fn, "r");
 66         if (!dfh) {
 67             if (errno == ENOENT)
 68                 err = 0;
 69             if (!err && nd<maxnode)
 70                 continue;
 71             else
 72                 break;
 73         }


There are no /sys/devices/system/node/node*/distance files on this system, so fopen (line 65) repeatedly fails and eventually it breaks out of the loop (line 72).

Then it continues with:

 89     free(line);
 90     if (err)  {
 91         numa_warn(W_distance,
 92               "Cannot parse distance information in sysfs: %s",
 93               strerror(errno));
 94         free(table);
 95         return err;
 96     }


The problem is that err is 0 due to line 68 above which considers ENOENT as a non-error, so it skips over this warning and continues with

106     distance_table = table;
107     return 0;
108 }

And table is still set to 0x0 (the initial value):

(gdb) p distance_table
$4 = (int *) 0x0

Which then leads to the segfault and crash here in distance.c:117
    return distance_table[a * distance_numnodes + b];


Why is ENOENT treated like a non-error?

 67             if (errno == ENOENT)
 68                 err = 0;

Version-Release number of selected component:
numactl-2.0.9-1.fc20

Additional info:
reporter:       libreport-2.2.0
backtrace_rating: 4
cmdline:        numactl --hardware
crash_function: numa_distance
executable:     /usr/bin/numactl
kernel:         3.13.7-200.nonuma.fc20.x86_64
runlevel:       N 5
type:           CCpp
uid:            0

Truncated backtrace:
Thread no. 1 (3 frames)
 #0 numa_distance at distance.c:117
 #1 print_distances at numactl.c:201
 #2 hardware at numactl.c:294