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Message-ID: <20241114-oberteil-villen-419f96aad840@brauner>
Date: Thu, 14 Nov 2024 15:48:00 +0100
From: Christian Brauner <brauner@...nel.org>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: Jeff Layton <jlayton@...nel.org>, Karel Zak <kzak@...hat.com>,
Ian Kent <raven@...maw.net>, Josef Bacik <josef@...icpanda.com>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH v4 0/3] fs: allow statmount to fetch the fs_subtype and
sb_source
On Thu, Nov 14, 2024 at 02:16:05PM +0100, Miklos Szeredi wrote:
> On Thu, 14 Nov 2024 at 13:29, Jeff Layton <jlayton@...nel.org> wrote:
>
> > Ordinarily, I might agree, but we're now growing a new mount option
> > field that has them separated by NULs. Will we need two extra fields
> > for this? One comma-separated, and one NUL separated?
> >
> > /proc/#/mountinfo and mounts prepend these to the output of
> > ->show_options, so the simple solution would be to just prepend those
> > there instead of adding a new field. FWIW, only SELinux has any extra
> > mount options to show here.
>
> Compromise: tack them onto the end of the comma separated list, but
> add a new field for the nul separated security options.
>
> I think this would be logical, since the comma separated list is more
> useful for having a /proc/$$/mountinfo compatible string than for
> actually interpreting what's in there.
Fair. Here's an incremental for the array of security options.
diff --git a/fs/namespace.c b/fs/namespace.c
index 4f39c4aba85d..a9065a9ab971 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -5072,13 +5072,30 @@ static int statmount_mnt_opts(struct kstatmount *s, struct seq_file *seq)
return 0;
}
+static inline int statmount_opt_unescape(struct seq_file *seq, char *buf_start)
+{
+ char *buf_end, *opt_start, *opt_end;
+ int count = 0;
+
+ buf_end = seq->buf + seq->count;
+ *buf_end = '\0';
+ for (opt_start = buf_start + 1; opt_start < buf_end; opt_start = opt_end + 1) {
+ opt_end = strchrnul(opt_start, ',');
+ *opt_end = '\0';
+ buf_start += string_unescape(opt_start, buf_start, 0, UNESCAPE_OCTAL) + 1;
+ if (WARN_ON_ONCE(++count == INT_MAX))
+ return -EOVERFLOW;
+ }
+ seq->count = buf_start - 1 - seq->buf;
+ return count;
+}
+
static int statmount_opt_array(struct kstatmount *s, struct seq_file *seq)
{
struct vfsmount *mnt = s->mnt;
struct super_block *sb = mnt->mnt_sb;
size_t start = seq->count;
- char *buf_start, *buf_end, *opt_start, *opt_end;
- u32 count = 0;
+ char *buf_start;
int err;
if (!sb->s_op->show_options)
@@ -5095,17 +5112,39 @@ static int statmount_opt_array(struct kstatmount *s, struct seq_file *seq)
if (seq->count == start)
return 0;
- buf_end = seq->buf + seq->count;
- *buf_end = '\0';
- for (opt_start = buf_start + 1; opt_start < buf_end; opt_start = opt_end + 1) {
- opt_end = strchrnul(opt_start, ',');
- *opt_end = '\0';
- buf_start += string_unescape(opt_start, buf_start, 0, UNESCAPE_OCTAL) + 1;
- if (WARN_ON_ONCE(++count == 0))
- return -EOVERFLOW;
- }
- seq->count = buf_start - 1 - seq->buf;
- s->sm.opt_num = count;
+ err = statmount_opt_unescape(seq, buf_start);
+ if (err < 0)
+ return err;
+
+ s->sm.opt_num = err;
+ return 0;
+}
+
+static int statmount_opt_sec_array(struct kstatmount *s, struct seq_file *seq)
+{
+ struct vfsmount *mnt = s->mnt;
+ struct super_block *sb = mnt->mnt_sb;
+ size_t start = seq->count;
+ char *buf_start;
+ int err;
+
+ buf_start = seq->buf + start;
+
+ err = security_sb_show_options(seq, sb);
+ if (!err)
+ return err;
+
+ if (unlikely(seq_has_overflowed(seq)))
+ return -EAGAIN;
+
+ if (seq->count == start)
+ return 0;
+
+ err = statmount_opt_unescape(seq, buf_start);
+ if (err < 0)
+ return err;
+
+ s->sm.opt_sec_num = err;
return 0;
}
@@ -5138,6 +5177,10 @@ static int statmount_string(struct kstatmount *s, u64 flag)
sm->opt_array = start;
ret = statmount_opt_array(s, seq);
break;
+ case STATMOUNT_OPT_SEC_ARRAY:
+ sm->opt_sec_array = start;
+ ret = statmount_opt_sec_array(s, seq);
+ break;
case STATMOUNT_FS_SUBTYPE:
sm->fs_subtype = start;
statmount_fs_subtype(s, seq);
@@ -5294,6 +5337,9 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id,
if (!err && s->mask & STATMOUNT_OPT_ARRAY)
err = statmount_string(s, STATMOUNT_OPT_ARRAY);
+ if (!err && s->mask & STATMOUNT_OPT_SEC_ARRAY)
+ err = statmount_string(s, STATMOUNT_OPT_SEC_ARRAY);
+
if (!err && s->mask & STATMOUNT_FS_SUBTYPE)
err = statmount_string(s, STATMOUNT_FS_SUBTYPE);
@@ -5323,7 +5369,7 @@ static inline bool retry_statmount(const long ret, size_t *seq_size)
#define STATMOUNT_STRING_REQ (STATMOUNT_MNT_ROOT | STATMOUNT_MNT_POINT | \
STATMOUNT_FS_TYPE | STATMOUNT_MNT_OPTS | \
STATMOUNT_FS_SUBTYPE | STATMOUNT_SB_SOURCE | \
- STATMOUNT_OPT_ARRAY)
+ STATMOUNT_OPT_ARRAY | STATMOUNT_OPT_SEC_ARRAY)
static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq,
struct statmount __user *buf, size_t bufsize,
diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
index c0fda4604187..569d938a5757 100644
--- a/include/uapi/linux/mount.h
+++ b/include/uapi/linux/mount.h
@@ -177,7 +177,9 @@ struct statmount {
__u32 sb_source; /* [str] Source string of the mount */
__u32 opt_num; /* Number of fs options */
__u32 opt_array; /* [str] Array of nul terminated fs options */
- __u64 __spare2[47];
+ __u32 opt_sec_num; /* Number of security options */
+ __u32 opt_sec_array; /* [str] Array of nul terminated security options */
+ __u64 __spare2[45];
char str[]; /* Variable size part containing strings */
};
@@ -214,6 +216,7 @@ struct mnt_id_req {
#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_... */
+#define STATMOUNT_OPT_SEC_ARRAY 0x00000800U /* Want/got opt_sec... */
/*
* Special @mnt_id values that can be passed to listmount
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