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    SubjectRe: [PATCH] fix filp_cachep memory corruption
    On Thu, 03 Feb 2011 04:18:58 +0900
    "J. R. Okajima" <hooanon05@yahoo.co.jp> wrote:

    >
    > commit e1ddf5b0dd3e8234581c78c3cadd6e2adfe6e2d4
    > Author: J. R. Okajima <hooanon05@yahoo.co.jp>
    > Date: Thu Feb 3 03:38:12 2011 +0900
    >
    > fix filp_cachep memory corruption
    >
    > By the commit
    > 31e6b01 2011-01-07 fs: rcu-walk for path lookup
    > the condition "-ESTALE && !LOOKUP_REVAL" is added to "goto reval" in
    > do_filp_open(), and it lookup again with LOOKUP_REVAL _after_
    > release_open_intent(). Since release_open_intent() is called by
    > do_last() and finish_open() too, add the same condition to all of them.
    >
    > Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
    >
    > diff --git a/fs/namei.c b/fs/namei.c
    > index 084be4d..1f62d6a 100644
    > --- a/fs/namei.c
    > +++ b/fs/namei.c
    > @@ -2269,7 +2269,8 @@ static struct file *finish_open(struct nameidata *nd,
    > return filp;
    >
    > exit:
    > - if (!IS_ERR(nd->intent.open.file))
    > + if (!(error == -ESTALE && !(nd->flags & LOOKUP_REVAL))
    > + && !IS_ERR(nd->intent.open.file))
    > release_open_intent(nd);
    > path_put(&nd->path);
    > return ERR_PTR(error);
    > @@ -2393,7 +2394,8 @@ exit_mutex_unlock:
    > exit_dput:
    > path_put_conditional(path, nd);
    > exit:
    > - if (!IS_ERR(nd->intent.open.file))
    > + if (!(error == -ESTALE && !(nd->flags & LOOKUP_REVAL))
    > + && !IS_ERR(nd->intent.open.file))
    > release_open_intent(nd);
    > path_put(&nd->path);
    > return ERR_PTR(error);
    > @@ -2564,7 +2566,8 @@ exit_dput:
    > out_path:
    > path_put(&nd.path);
    > out_filp:
    > - if (!IS_ERR(nd.intent.open.file))
    > + if (!(error == -ESTALE && !(flags & LOOKUP_REVAL))
    > + && !IS_ERR(nd.intent.open.file))
    > release_open_intent(&nd);
    > filp = ERR_PTR(error);
    > goto out;

    The patch is pretty ugly. It would be much nicer if we had a
    well-named and documented helper function to replace that repeated
    open-coded test. Not just because the code looks better - a standalone
    function is an opportunity to explain to readers what the code is
    trying to do.


    Anyway, as Nick appears to have done a dump-and-run on the kernel
    project, I shall send your fix into Linus as-is. Perhaps you or Nick
    could look into cleaning things up later on?



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