inode->i_rdev not initialized in 2.4 fs/inode.c, only in 2.6?

inode->i_rdev not initialized in 2.4 fs/inode.c, only in 2.6?

[Iustin Pop]

Hello,

I'm running 2.4.22 (with XFS and skas patch), but these patches do not
affect the code in question. /proc/version = Linux version 2.4.22-xfs
(root@saytrin) (gcc version 3.3.2 20030908 (Debian prerelease))

I get strange results (st.st_rdev != 0) in userspace after stat on some
non-devices regular file/directory. On one computer, /etc gives 773 and
/etc/init.d 0, while on another /etc gives 0 and /etc/init.d 13478.

After gdb and seeing it comes from kernel, I looked around and saw that
in fs/inode.c, i_rdev is not zeroed. Nor does it *seem* that
kmem_cache_alloc clears the memory, but I could be mistaken, it's
complicated code (I think it only clears at cache creation). And r_dev
is what gets transformed into st_rdev in fs/stat.c

2.6 fixes this behavior, by saying "inode->i_rdev = to_kdev_t(0);".
Shouldn't this be also in 2.4?

Thanks,
Iustin Pop

Please CC me as I'm not on the list.

Re: inode->i_rdev not initialized in 2.4 fs/inode.c, only in 2.6?

[viro]

On Tue, Oct 28, 2003 at 01:45:14AM +0200, Iustin Pop wrote:
> Hello,
> 
> I'm running 2.4.22 (with XFS and skas patch), but these patches do not
> affect the code in question. /proc/version = Linux version 2.4.22-xfs
> (root@saytrin) (gcc version 3.3.2 20030908 (Debian prerelease))
> 
> I get strange results (st.st_rdev != 0) in userspace after stat on some
> non-devices regular file/directory. On one computer, /etc gives 773 and
> /etc/init.d 0, while on another /etc gives 0 and /etc/init.d 13478.

st_rdev is undefined for non-devices, so any userland code that relies on
it being zero is broken.  It wouldn't hurt to zero it out, but any application
that has problems with that needs to be fixed anyway.