getcwd() problem on OSR6/MP1

[Roger Cornelius]

I'm seeing weird behaviour from getcwd() on OSR6/MP1. It fails
inexplicably in some cases, with errno of EACCES. I noticed the
problem with the mutt mailer, but here's a short program I used to test
with:

/* /tmp/getcwd.c */
#include <unistd.h>
main()
{
char *d;
if ((d = getcwd(NULL, 512)) == NULL)
perror();
else
printf("dir = %s\n", d);
}


Here's a typescript which illustrates the problem. I've added blank
lines to make it readable. Note that the test program fails when cd'd
to /u2 if invoker is not root.


Script started on Fri Feb 24 16:20:39 2006
$ id
uid=201(rac) gid=101(special) groups=101(special),50(group)

$ ls -ld /u1 /u2
drwxr-xr-x 11 root sys 2048 Aug 22 2005 /u1
drwxr-xr-x 5 root sys 96 Aug 15 2005 /u2

$ getacl /u1 /u2
# file: /u1
# owner: root
# group: sys
user::rwx
group::r-x
class:r-x
other:r-x

# file: /u2
# owner: root
# group: sys
user::rwx
group::r-x
class:r-x
other:r-x

$ df
Filesystem 1024-blocks Used Available Capacity Mounted on
/dev/root 7167998 2413744 4754254 34% /
/dev/boot 40959 6787 34172 17% /stand
/proc 0 0 0 - /proc
/dev/fd 0 0 0 - /dev/fd
/dev/_tcp 0 0 0 - /dev/_tcp
/dev/u 3071998 2314044 757954 76% /u
/dev/u1 24162644 23864852 297792 99% /u1
/dev/u2 8867870 2078538 6789332 24% /u2
/processorfs 0 0 0 -
/system/processor
/var/tmp 524288 24 524264 1% /var/tmp

$ cd /u1
$ pwd
/u1

$ /tmp/getcwd
dir = /u1

$ cd /u2
$ pwd
/u2

$ /tmp/getcwd
Permission denied

$ su
Password:

# /tmp/getcwd
dir = /u2
# $

script done on Fri Feb 24 16:21:50 2006

I did not include it above, but the test program works correctly when
cd'd to /u. The only difference I can see is that /u2 is on a second
disk. Filesystems are all vfxd.

Anyone have any ideas what might be wrong?

[Bela Lubkin]

Post by Roger Cornelius
I'm seeing weird behaviour from getcwd() on OSR6/MP1. It fails
inexplicably in some cases, with errno of EACCES. I noticed the
problem with the mutt mailer, but here's a short program I used to test
/* /tmp/getcwd.c */
#include <unistd.h>
main()
{
char *d;
if ((d = getcwd(NULL, 512)) == NULL)
perror();
else
printf("dir = %s\n", d);
}
Here's a typescript which illustrates the problem. I've added blank
lines to make it readable. Note that the test program fails when cd'd
to /u2 if invoker is not root.
Script started on Fri Feb 24 16:20:39 2006
$ id
uid=201(rac) gid=101(special) groups=101(special),50(group)
$ ls -ld /u1 /u2
drwxr-xr-x 11 root sys 2048 Aug 22 2005 /u1
drwxr-xr-x 5 root sys 96 Aug 15 2005 /u2
$ getacl /u1 /u2
# file: /u1
# owner: root
# group: sys
user::rwx
group::r-x
class:r-x
other:r-x
# file: /u2
# owner: root
# group: sys
user::rwx
group::r-x
class:r-x
other:r-x
$ df
Filesystem 1024-blocks Used Available Capacity Mounted on
/dev/root 7167998 2413744 4754254 34% /
/dev/boot 40959 6787 34172 17% /stand
/proc 0 0 0 - /proc
/dev/fd 0 0 0 - /dev/fd
/dev/_tcp 0 0 0 - /dev/_tcp
/dev/u 3071998 2314044 757954 76% /u
/dev/u1 24162644 23864852 297792 99% /u1
/dev/u2 8867870 2078538 6789332 24% /u2
/processorfs 0 0 0 -
/system/processor
/var/tmp 524288 24 524264 1% /var/tmp
$ cd /u1
$ pwd
/u1
$ /tmp/getcwd
dir = /u1
$ cd /u2
$ pwd
/u2
$ /tmp/getcwd
Permission denied
$ su
# /tmp/getcwd
dir = /u2
# $
script done on Fri Feb 24 16:21:50 2006
I did not include it above, but the test program works correctly when
cd'd to /u. The only difference I can see is that /u2 is on a second
disk. Filesystems are all vfxd.
Anyone have any ideas what might be wrong?

Yes! This goes back to a buggy behavior I remember seeing on Xenix and
possibly SCO Unix 3.2.0, maybe even a little later, but it was
eventually fixed.

It's a mounted filesystem. Current working directory is discovered in
reverse order (from leaf to root). The path from (say) /u2/foo/ is:
/u2/foo; /u2/. (the root of the mounted filesystem); /u2 (the
mounted-on directory on the root filesystem); /. While the filesystem
is mounted, you can only examine three of those. You can't see the
permissions of the mounted-on directory.

Try:

# umount /u2
# ls -ld /u2
[I predict it will have perms that deny world-execute == world-search]
# chmod 755 /u2
# mount /u2

Now all is well again. Right?

I say "buggy behavior" but I'm not sure I can prove that the perms of
the underlying (mounted-on) directory _should_ be ignored. I know that
OSR5 does ignore them, and my guess is that OSR6 doesn't, as
demonstrated on your system.

Post by Roger Cornelius
Bela<

[Roger Cornelius]

Post by Bela Lubkin

Post by Roger Cornelius
I'm seeing weird behaviour from getcwd() on OSR6/MP1. It fails
inexplicably in some cases, with errno of EACCES. I noticed the
problem with the mutt mailer, but here's a short program I used to test
/* /tmp/getcwd.c */
#include <unistd.h>
main()
{
char *d;
if ((d = getcwd(NULL, 512)) == NULL)
perror();
else
printf("dir = %s\n", d);
}
Here's a typescript which illustrates the problem. I've added blank
lines to make it readable. Note that the test program fails when cd'd
to /u2 if invoker is not root.
Script started on Fri Feb 24 16:20:39 2006
$ id
uid=201(rac) gid=101(special) groups=101(special),50(group)
$ ls -ld /u1 /u2
drwxr-xr-x 11 root sys 2048 Aug 22 2005 /u1
drwxr-xr-x 5 root sys 96 Aug 15 2005 /u2
$ getacl /u1 /u2
# file: /u1
# owner: root
# group: sys
user::rwx
group::r-x
class:r-x
other:r-x
# file: /u2
# owner: root
# group: sys
user::rwx
group::r-x
class:r-x
other:r-x
$ df
Filesystem 1024-blocks Used Available Capacity Mounted on
/dev/root 7167998 2413744 4754254 34% /
/dev/boot 40959 6787 34172 17% /stand
/proc 0 0 0 - /proc
/dev/fd 0 0 0 - /dev/fd
/dev/_tcp 0 0 0 - /dev/_tcp
/dev/u 3071998 2314044 757954 76% /u
/dev/u1 24162644 23864852 297792 99% /u1
/dev/u2 8867870 2078538 6789332 24% /u2
/processorfs 0 0 0 -
/system/processor
/var/tmp 524288 24 524264 1% /var/tmp
$ cd /u1
$ pwd
/u1
$ /tmp/getcwd
dir = /u1
$ cd /u2
$ pwd
/u2
$ /tmp/getcwd
Permission denied
$ su
# /tmp/getcwd
dir = /u2
# $
script done on Fri Feb 24 16:21:50 2006
I did not include it above, but the test program works correctly when
cd'd to /u. The only difference I can see is that /u2 is on a second
disk. Filesystems are all vfxd.
Anyone have any ideas what might be wrong?

Yes! This goes back to a buggy behavior I remember seeing on Xenix and
possibly SCO Unix 3.2.0, maybe even a little later, but it was
eventually fixed.
It's a mounted filesystem. Current working directory is discovered in
/u2/foo; /u2/. (the root of the mounted filesystem); /u2 (the
mounted-on directory on the root filesystem); /. While the filesystem
is mounted, you can only examine three of those. You can't see the
permissions of the mounted-on directory.
# umount /u2
# ls -ld /u2
[I predict it will have perms that deny world-execute == world-search]
# chmod 755 /u2
# mount /u2
Now all is well again. Right?

Yes, that was exactly it. Thanks once again for your kind
illumination. It would never have occurred to me to check this.

Post by Bela Lubkin
I say "buggy behavior" but I'm not sure I can prove that the perms of
the underlying (mounted-on) directory _should_ be ignored. I know that
OSR5 does ignore them, and my guess is that OSR6 doesn't, as
demonstrated on your system.

Post by Roger Cornelius
Bela<