From: Trond Myklebust <trondmy@kernel.org>
To: rtm@csail.mit.edu, Anna Schumaker <anna@kernel.org>
Cc: linux-nfs@vger.kernel.org
Subject: Re: _nfs4_open_and_get_state() should check d_splice_alias() return for error
Date: Sun, 07 Sep 2025 17:08:45 -0400 [thread overview]
Message-ID: <8fcebbadae40f048802c3725a231667b8ac25550.camel@kernel.org> (raw)
In-Reply-To: <23296.1757267766@localhost>
On Sun, 2025-09-07 at 13:56 -0400, rtm@csail.mit.edu wrote:
> [You don't often get email from rtm@csail.mit.edu. Learn why this is
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>
> In this code in fs/nfs/nfs4proc.c _nfs_open_and_get_state():
>
> dentry = opendata->dentry;
> if (d_really_is_negative(dentry)) {
> struct dentry *alias;
> d_drop(dentry);
> alias = d_splice_alias(igrab(state->inode), dentry);
> /* d_splice_alias() can't fail here - it's a non-
> directory */
> if (alias) {
> dput(ctx->dentry);
> ctx->dentry = dentry = alias;
> }
>
> d_splice_alias() can fail, returning ERR_PTR(-ELOOP). Then this call
> later on causes a crash:
No. It can't return ELOOP.
The reason why it can't is that OP_OPEN is not allowed to return
NFS4_OK for anything other than a regular file. Hence the server cannot
return a directory, or anything which could otherwise be an ancestor to
'dentry'. Hence the comment above...
IOW: Your implementation of OP_OPEN is broken because it only returns
either NFS4ERR_NOENT or NFS4_OK, whereas in this case it should clearly
have return NFS4ERR_ISDIR.
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trondmy@kernel.org, trond.myklebust@hammerspace.com
prev parent reply other threads:[~2025-09-07 21:08 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-07 17:56 _nfs4_open_and_get_state() should check d_splice_alias() return for error rtm
2025-09-07 21:08 ` Trond Myklebust [this message]
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