Re: Bug#285281: core dump on amd64 (gcc-3.4)

[Kay Sievers <kay.sievers@vrfy.org>]

On Wed, 2004-12-15 at 09:50 +0100, Marco d'Itri wrote:
> clsdev->directory is NULL, is this a bug in libsysfs or udev?
> Apparently this only happens on amd64.
> 
> ----- Forwarded message from martin-deb@zero-based.org -----

> #0  0x0000000000403024 in sysfs_get_classdev_attr (clsdev=0x518260, name=0x40dcac "dev") at libsysfs/sysfs_class.c:643
> 643             if (clsdev->directory->subdirs = NULL) 
> (gdb) backtrace

It is caused by the vc class behavior, to emit events on every open()
and close(). We get a lot of events on bootup for every vc device, cause
it is several times reopened. This causes the sysfs-dir to go away while
the device is opened in libsysfs. This simple test program:

#include <stdio.h>
#include <unistd.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <errno.h>

#include "libsysfs/sysfs/libsysfs.h"


int main(int argc, char *argv[], char *envp[])
{
        struct sysfs_class_device *class_dev;
        struct sysfs_attribute *attr;

        mkdir("test-sys", 0775);
        mkdir("test-sys/class", 0775);
        mkdir("test-sys/class/test", 0775);

        setenv("SYSFS_PATH", "test-sys", 1);

        printf("open\n");
        class_dev = sysfs_open_class_device_path("test-sys/class/test");
        printf("%p\n", class_dev);

        printf("rmdir\n");
        rmdir("test-sys/class/test");

        printf("read attr\n");
        attr = sysfs_get_classdev_attr(class_dev, "dev");
}

segfaults every time:
  [kay@pim udev.kay]$ gcc -g -I libsysfs/sysfs -I libsysfs -o bug bug.c libsysfs/sysfs.a
  [kay@pim udev.kay]$ ./bug 
  open
  0x804f0d8
  rmdir
  read attr
  Segmentation fault


This seems to fix it:

=== libsysfs/sysfs_class.c 1.11 vs edited ==--- 1.11/libsysfs/sysfs_class.c 2004-10-20 05:15:26 +02:00
+++ edited/libsysfs/sysfs_class.c       2004-12-15 14:20:13 +01:00
@@ -640,6 +640,9 @@
                        return cur;
        }
 
+       if (clsdev->directory = NULL)
+               return NULL;
+
        if (clsdev->directory->subdirs = NULL) 
                if ((sysfs_read_dir_subdirs(clsdev->directory)) != 0 ||
                    clsdev->directory->subdirs = NULL) 


Thanks,
Kay



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