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 A060420B20; Tue, 8 Oct 2024 18:19:27 +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=1728411567; cv=none; b=JVX7MmlZqLFf8tK9fexEDvFsV48VzIiqy6yP8ImH7M2J8Q8zTlF5G9jZDaxWYs+c5KKFZCF8Rpx/Zqbn6oM+fqw+8FAnp1iVLRMgCUbpHk3Z10PdA5QZQ6lw8+XMzceiwHdy1gqBdsfuNntSqcdLA1gcLqGgMB63tXhPjnaFIZ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728411567; c=relaxed/simple; bh=z54KckxhgJG3g7xIM1xPAckD2eOaytBEiXST0+QTFi8=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=RbxwXJIbpOBQeAFJLGUTqIJdbNIEZwDU1DYbPyru1ogYKemYT+EGbAzuxB8dJja3WR47cF+LQ8cTNuKWkawFgLhIDfYU7nYwqPhvWap570vC2PucO1aj268UiRzI2RWBwj6RhWLQv3EzZw5y1KXd3Zce/eRlLK6gLlD1mjHScrA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JLs0bV1F; 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="JLs0bV1F" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7FB3FC4CEC7; Tue, 8 Oct 2024 18:19:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728411567; bh=z54KckxhgJG3g7xIM1xPAckD2eOaytBEiXST0+QTFi8=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=JLs0bV1F3aUUl1juIVgv1kMHK/xtpxJPD91j5csNJEONaEBx7Sx6IiGMVo0b+zSv/ IQy2DRQNoHAf8kvZbyRsaDvYiOZ18ww7oOnNlnpOIATEGjKgEdWH8NSxcRl/z/BBk6 FQ3hLKIUq3IHn/PfmoKsgrM6TNBPoxJJz097Z9MqIg3gWDIYVMLPmDXSfm+glQHrqp rnWwZf/4kfRVaUJxHAeqqmnEX9gyGQGu9SHHTj7lw2LoTAnx9Xl1kLdkPAPmMHGPEk 4xJYdvSJUqNJhAZF7KwpbrrQ52G/U+PbX3GPWRrGviUyd2gUw4JadxGL7TPawF73WR 2x1mlC2/LFsUA== Message-ID: Subject: Re: [PATCH v3 1/3] fs: prepare for "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 14:19:25 -0400 In-Reply-To: <20241008152118.453724-2-amir73il@gmail.com> References: <20241008152118.453724-1-amir73il@gmail.com> <20241008152118.453724-2-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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the high 16bit of the handle_type field to encode > file handle traits, such as "connectable". >=20 > In preparation for this change, make sure that filesystems do not return > a handle_type value with upper bits set and that the open_by_handle_at(2) > syscall rejects these handle types. >=20 > Signed-off-by: Amir Goldstein > --- > fs/exportfs/expfs.c | 14 ++++++++++++-- > fs/fhandle.c | 6 ++++++ > include/linux/exportfs.h | 14 ++++++++++++++ > 3 files changed, 32 insertions(+), 2 deletions(-) >=20 > diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c > index 4f2dd4ab4486..c8eb660fdde4 100644 > --- a/fs/exportfs/expfs.c > +++ b/fs/exportfs/expfs.c > @@ -382,14 +382,21 @@ int exportfs_encode_inode_fh(struct inode *inode, s= truct fid *fid, > int *max_len, struct inode *parent, int flags) > { > const struct export_operations *nop =3D inode->i_sb->s_export_op; > + enum fid_type type; > =20 > if (!exportfs_can_encode_fh(nop, flags)) > return -EOPNOTSUPP; > =20 > if (!nop && (flags & EXPORT_FH_FID)) > - return exportfs_encode_ino64_fid(inode, fid, max_len); > + type =3D exportfs_encode_ino64_fid(inode, fid, max_len); > + else > + type =3D nop->encode_fh(inode, fid->raw, max_len, parent); > + > + if (WARN_ON_ONCE(FILEID_USER_FLAGS(type))) > + return -EINVAL; > + The stack trace won't be very useful here. Rather than a WARN, it might be better to dump out some info about the fstype (and maybe other info?) that returned the bogus type value here. I'm pretty sure most in-kernel fs's don't do this, but who knows what 3rd party fs's might do. > + return type; > =20 > - return nop->encode_fh(inode, fid->raw, max_len, parent); > } > EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh); > =20 > @@ -436,6 +443,9 @@ exportfs_decode_fh_raw(struct vfsmount *mnt, struct f= id *fid, int fh_len, > char nbuf[NAME_MAX+1]; > int err; > =20 > + if (WARN_ON_ONCE(FILEID_USER_FLAGS(fileid_type))) > + return -EINVAL; > + This is called from do_handle_to_path() or nfsd_set_fh_dentry(), which means that this fh comes from userland or from an NFS client. I don't think we want to WARN because someone crafted a bogus fh and passed it to us. > /* > * Try to get any dentry for the given file handle from the filesystem. > */ > diff --git a/fs/fhandle.c b/fs/fhandle.c > index 82df28d45cd7..c5792cf3c6e9 100644 > --- a/fs/fhandle.c > +++ b/fs/fhandle.c > @@ -307,6 +307,10 @@ static int handle_to_path(int mountdirfd, struct fil= e_handle __user *ufh, > retval =3D -EINVAL; > goto out_path; > } > + if (!FILEID_USER_TYPE_IS_VALID(f_handle.handle_type)) { > + retval =3D -EINVAL; > + goto out_path; > + } > handle =3D kmalloc(struct_size(handle, f_handle, f_handle.handle_bytes)= , > GFP_KERNEL); > if (!handle) { > @@ -322,6 +326,8 @@ static int handle_to_path(int mountdirfd, struct file= _handle __user *ufh, > goto out_handle; > } > =20 > + /* 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); > =20 > out_handle: > diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h > index 893a1d21dc1c..76a3050b3593 100644 > --- a/include/linux/exportfs.h > +++ b/include/linux/exportfs.h > @@ -160,6 +160,20 @@ struct fid { > #define EXPORT_FH_FID 0x2 /* File handle may be non-decodeable */ > #define EXPORT_FH_DIR_ONLY 0x4 /* Only decode file handle for a director= y */ > =20 > +/* > + * Filesystems use only lower 8 bits of file_handle type for fid_type. > + * name_to_handle_at() uses upper 16 bits of type as user flags to be > + * interpreted by open_by_handle_at(). > + */ > +#define FILEID_USER_FLAGS_MASK 0xffff0000 > +#define FILEID_USER_FLAGS(type) ((type) & FILEID_USER_FLAGS_MASK) > + > +/* Flags supported in encoded handle_type that is exported to user */ > +#define FILEID_VALID_USER_FLAGS (0) > + > +#define FILEID_USER_TYPE_IS_VALID(type) \ > + (!(FILEID_USER_FLAGS(type) & ~FILEID_VALID_USER_FLAGS)) > + > /** > * struct export_operations - for nfsd to communicate with file systems > * @encode_fh: encode a file handle fragment from a dentry The rest looks reasonable. --=20 Jeff Layton