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 EA8671CD218; Tue, 12 Nov 2024 12:20:05 +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=1731414006; cv=none; b=EhJs8WNDVtFcYDRRYzVsMbna5NHO8zZgvgge5VylCnN9Qz/Pvqc+9ctxexlZpjjaX3lxxRaSrKEN2rpUtFmiQDB+XXLxg6bRJqdvFawbjt1rvNtoG7g8leumux8FaonXj4ElWsPAwxpyo5v4rWcrpByFCMiERuV53Gun7CFW+zo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731414006; c=relaxed/simple; bh=NeCS+o94jbktdL4jV/mzav8wOjxmbd7d7nRqgBNRQyc=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=liU3lUw7Pp1TMinJwkEKyQ9LQSq16CYhQOMPUHWxo+5gWxdlGBiarlZVXPruIIxbRQSHdRHEPhQ92NNGPlzN5RPL1w78JhMWlLKkFXDdv0qcn7DRPyTe02OYjSfcAG74tLDSYyU9sHkM+1b0GwEvsQZMFNqSUoVDeCr5FBZVhNY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bc0VV3md; 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="bc0VV3md" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D540FC4CED0; Tue, 12 Nov 2024 12:20:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1731414005; bh=NeCS+o94jbktdL4jV/mzav8wOjxmbd7d7nRqgBNRQyc=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=bc0VV3mdRX2CkhdozhkVXkF0EmEZLwv/5w8y/GN/fgB6OW8EfJ9uzSHx3zB41yijC y24ExCt0orNuo1Yzmly0WAloWLrsDUMhaKLt3F97uYWOHd8zWNgAqiwXA7Gpeg63fz TL5mPfFydUzwaz9bUc06Bc0pjh56AQErJvlBcaT2q/vNd3A5f3yScRbYaPFYsV+sBr 456VwrE6BQy10yAKDVz3GUqQJ1s0xunq523JLEM+vkDeqWwPblpuIbSZSqWErK7pU5 HB6t6oVDw7VLy2GhNqHr1T8KEWQahPWtSQ24fF65oW1fSrpcMv3g45k0dVLknYKPy0 3FxLTuVE7euvA== Message-ID: <2faa89f0ad18d8f8015f65b202f8ddc64a810a71.camel@kernel.org> Subject: Re: [PATCH] statmount: add flag to retrieve unescaped options From: Jeff Layton To: Miklos Szeredi , linux-fsdevel@vger.kernel.org Cc: linux-api@vger.kernel.org, Karel Zak , Christian Brauner , Josef Bacik Date: Tue, 12 Nov 2024 07:20:03 -0500 In-Reply-To: <20241112101006.30715-1-mszeredi@redhat.com> References: <20241112101006.30715-1-mszeredi@redhat.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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retrieved with STATMOUNT_MNT_OPTS, which > returns a string of comma separated options, where some characters are > escaped using the \OOO notation. >=20 > Add a new flag, STATMOUNT_OPT_ARRAY, which instead returns the raw > option values separated with '\0' charaters. >=20 > Since escaped charaters are rare, this inteface is preferable for > non-libmount users which likley don't want to deal with option > de-escaping. >=20 > Example code: >=20 > if (st->mask & STATMOUNT_OPT_ARRAY) { > const char *opt =3D st->str + st->opt_array; >=20 > for (unsigned int i =3D 0; i < st->opt_num; i++) { > printf("opt_array[%i]: <%s>\n", i, opt); > opt +=3D strlen(opt) + 1; > } > } >=20 If the options are separated by NULs, how does userland know where to stop? At some point we will probably end up adding a new string value that would go after the opt array, and userland will need some way to clearly tell where that new string begins and the NUL-terminated options array ends. > Signed-off-by: Miklos Szeredi > --- > fs/namespace.c | 42 ++++++++++++++++++++++++++++++++++++++ > include/uapi/linux/mount.h | 7 +++++-- > 2 files changed, 47 insertions(+), 2 deletions(-) >=20 > diff --git a/fs/namespace.c b/fs/namespace.c > index 9a4ab1bc8b94..a16f75011610 100644 > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -5074,6 +5074,41 @@ static int statmount_mnt_opts(struct kstatmount *s= , struct seq_file *seq) > return 0; > } > =20 > +static int statmount_opt_array(struct kstatmount *s, struct seq_file *se= q) > +{ > + struct vfsmount *mnt =3D s->mnt; > + struct super_block *sb =3D mnt->mnt_sb; > + size_t start =3D seq->count; > + u32 count =3D 0; > + char *p, *end, *next, *u =3D seq->buf + start; > + int err; > + > + if (!sb->s_op->show_options) > + return 0; > + > + err =3D sb->s_op->show_options(seq, mnt->mnt_root); > + if (err) > + return err; > + > + if (unlikely(seq_has_overflowed(seq))) > + return -EAGAIN; > + > + end =3D seq->buf + seq->count; > + *end =3D '\0'; > + for (p =3D u + 1; p < end; p =3D next + 1) { > + next =3D strchrnul(p, ','); > + *next =3D '\0'; > + u +=3D string_unescape(p, u, 0, UNESCAPE_OCTAL) + 1; > + count++; > + if (!count) > + return -EOVERFLOW; > + } > + seq->count =3D u - 1 - seq->buf; > + s->sm.opt_num =3D count; > + > + return 0; > +} > + > static int statmount_string(struct kstatmount *s, u64 flag) > { > int ret =3D 0; > @@ -5099,6 +5134,10 @@ static int statmount_string(struct kstatmount *s, = u64 flag) > sm->mnt_opts =3D start; > ret =3D statmount_mnt_opts(s, seq); > break; > + case STATMOUNT_OPT_ARRAY: > + sm->opt_array =3D start; > + ret =3D statmount_opt_array(s, seq); > + break; > case STATMOUNT_FS_SUBTYPE: > sm->fs_subtype =3D start; > statmount_fs_subtype(s, seq); > @@ -5252,6 +5291,9 @@ static int do_statmount(struct kstatmount *s, u64 m= nt_id, u64 mnt_ns_id, > if (!err && s->mask & STATMOUNT_MNT_OPTS) > err =3D statmount_string(s, STATMOUNT_MNT_OPTS); > =20 > + if (!err && s->mask & STATMOUNT_OPT_ARRAY) > + err =3D statmount_string(s, STATMOUNT_OPT_ARRAY); > + > if (!err && s->mask & STATMOUNT_FS_SUBTYPE) > err =3D statmount_string(s, STATMOUNT_FS_SUBTYPE); > =20 > diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h > index 2b49e9131d77..c0fda4604187 100644 > --- a/include/uapi/linux/mount.h > +++ b/include/uapi/linux/mount.h > @@ -154,7 +154,7 @@ struct mount_attr { > */ > struct statmount { > __u32 size; /* Total size, including strings */ > - __u32 mnt_opts; /* [str] Mount options of the mount */ > + __u32 mnt_opts; /* [str] Options (comma separated, escaped) */ > __u64 mask; /* What results were written */ > __u32 sb_dev_major; /* Device ID */ > __u32 sb_dev_minor; > @@ -175,7 +175,9 @@ struct statmount { > __u64 mnt_ns_id; /* ID of the mount namespace */ > __u32 fs_subtype; /* [str] Subtype of fs_type (if any) */ > __u32 sb_source; /* [str] Source string of the mount */ > - __u64 __spare2[48]; > + __u32 opt_num; /* Number of fs options */ > + __u32 opt_array; /* [str] Array of nul terminated fs options */ > + __u64 __spare2[47]; > char str[]; /* Variable size part containing strings */ > }; > =20 > @@ -211,6 +213,7 @@ struct mnt_id_req { > #define STATMOUNT_MNT_OPTS 0x00000080U /* Want/got mnt_opts */ > #define STATMOUNT_FS_SUBTYPE 0x00000100U /* Want/got fs_subtype */ > #define STATMOUNT_SB_SOURCE 0x00000200U /* Want/got sb_source */ > +#define STATMOUNT_OPT_ARRAY 0x00000400U /* Want/got opt_... */ > =20 > /* > * Special @mnt_id values that can be passed to listmount --=20 Jeff Layton