problems with latest smbfs changes on 2.4.34 and security backports

Hi!

I have discovered a problem with the changes applied to smbfs in 2.4.34 and
in the security backports like last Debian's 2.4 kernel update these changes
seem to be made to solve CVE-2006-5871 and they have broken symbolic links
and changed the way that special files (like devices) are seen.

For example:
Before: symbolic links were seen as that, symbolic links an thus if you tried
to open the file the link was followed and you ended up reading the
destination file
Now: symbolic links are seen as normal files (at least with a ls) but their
length (N) is the length of the symbolic link, if you read it, you'll get the
first N characters of the destination file. For example, on my filesystem
bin/sh is a symlink to bash, thus it is 4 bytes long, if I to a cat bin/sh I
get ELF (this is, the first 4 characters of the bash program, first one
being a DEL).

Another example:
Before: if you did a ls of a device file, like dev/zero you could see it as
a device, if you tried opening it, it wouldn't work, but if you did a cp -a
of that file to a local filesystem the result was a working zero device.
Now: the devices are seen as normal files with a length of 0 bytes.

Seems to me like a mask is erasing some mode bits that shouldn't be erased.

I have carried my tests on a Debian Sarge machine always mounting the share
using: smbmount //server/share /mnt without any other options. The tests
were carried on a unpatched 2.4.34 comparing it to 2.4.33 and also on
Debian's 2.4.27 comparing 2.4.27-10sarge4 vs -10sarge5. The server is a
samba 3.0.23d and I have experienced the same behaviour with samba's
unix extensions = yes and unix extensions = no.

I don't know what else to add, if you need any more info or want me to do
any tests just ask for it.

Regards...
--
Santiago García Mantiñán
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Relevant Pages

  • Re: problems with latest smbfs changes on 2.4.34 and security backports
    ... in the security backports like last Debian's 2.4 kernel update these changes ... symbolic links were seen as that, symbolic links an thus if you tried ... Debian's 2.4.27 comparing 2.4.27-10sarge4 vs -10sarge5. ... do you still have your samba server ready to try to reproduce this ...
    (Linux-Kernel)
  • Re: problems with latest smbfs changes on 2.4.34 and security backports
    ... in the security backports like last Debian's 2.4 kernel update these changes ... symbolic links were seen as that, symbolic links an thus if you tried ... Debian's 2.4.27 comparing 2.4.27-10sarge4 vs -10sarge5. ... do you still have your samba server ready to try to reproduce this ...
    (Linux-Kernel)