From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1FE991E0DDD; Tue, 8 Oct 2024 18:37:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728412640; cv=none; b=k55kBfeop54p9jfoWuRut6ULF/EHvg9JGdcr0em5zj6mb6b0NkSkSD68tWAKx6Rgf2I6QcvYr9SpHxjbcWm2znXRgvXinPtwr59MIplWOksYqmKksJEIQWzgG6qxxX8khqPsyryR0yJfF+/d/wpotBlKliuXP/D0uGuwpY4A0mA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728412640; c=relaxed/simple; bh=JN7FYQviyirjPFA+WtNSib5/mPHM9CPS3S7oRFW8B10=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=pgczN4EcjPiUg0aslvTJgiSQMWuqntlBG0dcPR2872qFymWSaqoYOCogF7sej6zE2tF3FkYaUR9iWxgh0smge8VGARDOuvUcj8SLWdc0tBmHFM2J+RXu4yeIrxB4yV5R9Gd7/sZU0jhPk9VdBXDTxi5+DmE1OmRyTio/eaYNkZs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=to4X9MHn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="to4X9MHn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2177BC4CEC7; Tue, 8 Oct 2024 18:37:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728412639; bh=JN7FYQviyirjPFA+WtNSib5/mPHM9CPS3S7oRFW8B10=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=to4X9MHnDhmYHUrND/322o0HLt5sUPaNxXQlhpZoa7Bi45DgRKSp1UCHs0cpAYpHU 2ObwSPpKCELYDS9GozjHcFQUxNkeoCO+p8l0XBDfQN5L5eHDbx9si6Qplc5h4IOmBS ah6sDTgwOf6TOgrbZ7Z/9Ws6SR+sz94CZgWksoxbaez4jCsZwHvrOKunaxuHg/6/oN ff1CPGVnQxt0UjyMwsedV2IqMTOLeXDMYzazQO3pw5yXU2JIic4DfTcXEFx6RaqLdW WYod7rOcZfCVmhHW3gK3p/Ag5+QaeGRLz1jpOpgMuoAjjI7zMQFByy5IPUBrMq8W2w XNvG7TG6Uxwhg== Message-ID: Subject: Re: [PATCH v3 3/3] fs: open_by_handle_at() support for decoding "explicit connectable" file handles From: Jeff Layton To: Amir Goldstein Cc: Christian Brauner , Jan Kara , Aleksa Sarai , Chuck Lever , linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org Date: Tue, 08 Oct 2024 14:37:18 -0400 In-Reply-To: <20241008152118.453724-4-amir73il@gmail.com> References: <20241008152118.453724-1-amir73il@gmail.com> <20241008152118.453724-4-amir73il@gmail.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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open_by_handle_at(2) about the type format of "explicit connectable= " > file handles that were created using the AT_HANDLE_CONNECTABLE flag to > name_to_handle_at(2). >=20 > When decoding an "explicit connectable" file handles, name_to_handle_at(2= ) > should fail if it cannot open a "connected" fd with known path, which is > accessible (to capable user) from mount fd path. >=20 > Note that this does not check if the path is accessible to the calling > user, just that it is accessible wrt the mount namesapce, so if there > is no "connected" alias, or if parts of the path are hidden in the > mount namespace, open_by_handle_at(2) will return -ESTALE. >=20 > Signed-off-by: Amir Goldstein > --- > fs/fhandle.c | 20 +++++++++++++++++++- > include/linux/exportfs.h | 2 +- > 2 files changed, 20 insertions(+), 2 deletions(-) >=20 > diff --git a/fs/fhandle.c b/fs/fhandle.c > index 7b4c8945efcb..6a5458c3c6c9 100644 > --- a/fs/fhandle.c > +++ b/fs/fhandle.c > @@ -246,7 +246,13 @@ static int vfs_dentry_acceptable(void *context, stru= ct dentry *dentry) > =20 > if (!(ctx->flags & HANDLE_CHECK_SUBTREE) || d =3D=3D root) > retval =3D 1; > - WARN_ON_ONCE(d !=3D root && d !=3D root->d_sb->s_root); > + /* > + * exportfs_decode_fh_raw() does not call acceptable() callback with > + * a disconnected directory dentry, so we should have reached either > + * mount fd directory or sb root. > + */ > + if (ctx->fh_flags & EXPORT_FH_DIR_ONLY) > + WARN_ON_ONCE(d !=3D root && d !=3D root->d_sb->s_root); I don't quite get the test for EXPORT_FH_DIR_ONLY here. Why does this change require that instead of just continuing to WARN unconditionally? > dput(d); > return retval; > } > @@ -349,6 +355,7 @@ static int handle_to_path(int mountdirfd, struct file= _handle __user *ufh, > retval =3D -EINVAL; > goto out_path; > } > + > handle =3D kmalloc(struct_size(handle, f_handle, f_handle.handle_bytes)= , > GFP_KERNEL); > if (!handle) { > @@ -364,6 +371,17 @@ static int handle_to_path(int mountdirfd, struct fil= e_handle __user *ufh, > goto out_handle; > } > =20 > + /* > + * If handle was encoded with AT_HANDLE_CONNECTABLE, verify that we > + * are decoding an fd with connected path, which is accessible from > + * the mount fd path. > + */ > + if (f_handle.handle_type & FILEID_IS_CONNECTABLE) { > + ctx.fh_flags |=3D EXPORT_FH_CONNECTABLE; > + ctx.flags |=3D HANDLE_CHECK_SUBTREE; > + } > + if (f_handle.handle_type & FILEID_IS_DIR) > + ctx.fh_flags |=3D EXPORT_FH_DIR_ONLY; > /* Filesystem code should not be exposed to user flags */ > handle->handle_type &=3D ~FILEID_USER_FLAGS_MASK; > retval =3D do_handle_to_path(handle, path, &ctx); > diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h > index 230b0e1d669d..a48d4c94ff74 100644 > --- a/include/linux/exportfs.h > +++ b/include/linux/exportfs.h > @@ -171,7 +171,7 @@ struct fid { > /* Flags supported in encoded handle_type that is exported to user */ > #define FILEID_IS_CONNECTABLE 0x10000 > #define FILEID_IS_DIR 0x40000 > -#define FILEID_VALID_USER_FLAGS (0) > +#define FILEID_VALID_USER_FLAGS (FILEID_IS_CONNECTABLE | FILEID_IS_DIR) > =20 > #define FILEID_USER_TYPE_IS_VALID(type) \ > (!(FILEID_USER_FLAGS(type) & ~FILEID_VALID_USER_FLAGS)) --=20 Jeff Layton