Re: [PATCH] vfs: use kstrdup()

From: Cyrill Gorcunov
Date: Mon Jul 21 2008 - 03:10:10 EST

[Al Viro - Mon, Jul 21, 2008 at 08:03:46AM +0100]
| On Mon, Jul 21, 2008 at 02:29:47PM +0800, Li Zefan wrote:
| > > FWIW, it _is_ a good question.
| > >
| > > * is all code treating ->mnt_devname as optional? AFAICS, there's
| > > at least one place in NFS that doesn't. We could treat failing allocation
| > > the same way we treat failing allocation of vfsmount itself - callers can
| > > cope with that already.
| >
| > I just did a cleanup, and the original code didn't check for NULL.
| I know.
| > I just looked into the git history, and I found out since fs/namespace.c was
| > created in v2.4.10.4, the code has never changed to check for failing
| > allocation of ->mnt_devname.
| It used to have no users beyond fs/namespace.c itself and for _those_ the
| thing had been optional, so leaving NULL had been OK. Unfortunately, it
| still had been a bad idea - new users had appeared and those predictably
| didn't notice that fun detail.
| The right thing here is to consider failing allocation of ->mnt_devname
| as failure of the entire alloc.

Hi Al,

thanks a lot for comments! I think it is more then enough for now (i'm
about failing allocation in whole). If that happens and we are not able
to duplicate string - it's quite probable we will be in serious troubles
soon anyway ('cause of further kmalloc calls). So it's better to get
mount allocation fails then NULL deref.

- Cyrill -
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