2023-12-20 09:15:28

by Dongliang Cui

Subject: [PATCH]eventfs: Apply the gid in the mounting parameters to all files

I found that in the latest version, the nodes of
tracefs have been changed to dynamically created.

This has caused me to encounter a problem where
the gid I specified in the mounting parameters
cannot apply to all files, as in the following
situation:

/data/tmp/events # mount | grep tracefs
tracefs on /data/tmp type tracefs (rw,seclabel,relatime,gid=3012)

gid 3012 = readtracefs

/data/tmp # ls -lh
total 0
-r--r----- 1 root readtracefs 0 1970-01-01 08:00 README
-r--r----- 1 root readtracefs 0 1970-01-01 08:00 available_events

ums9621_1h10:/data/tmp/events # ls -lh
total 0
drwxr-xr-x 2 root root 0 2023-12-19 00:56 alarmtimer
drwxr-xr-x 2 root root 0 2023-12-19 00:56 asoc

It will prevent certain applications from accessing
tracefs properly, I try to avoid this issue by making
the following modifications.

Signed-off-by: Dongliang Cui <[email protected]>
---
fs/tracefs/inode.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index ae648de..5296ff7 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -560,6 +560,16 @@ struct dentry *eventfs_failed_creating(struct dentry *dentry)
*/
struct dentry *eventfs_end_creating(struct dentry *dentry)
{
+ struct tracefs_fs_info *fsi;
+ struct tracefs_mount_opts *opts;
+
+ if (dentry && dentry->d_inode) {
+ fsi = dentry->d_inode->i_sb->s_fs_info;
+ opts = &fsi->mount_opts;
+ if (opts->opts & BIT(Opt_gid))
+ change_gid(dentry, opts->gid);
+ }
+
return dentry;
}

--
2.7.4

2023-12-20 13:30:03

by Steven Rostedt

Subject: Re: [PATCH]eventfs: Apply the gid in the mounting parameters to all files

On Wed, 20 Dec 2023 17:15:06 +0800
Dongliang Cui <[email protected]> wrote:

> I found that in the latest version, the nodes of
> tracefs have been changed to dynamically created.
>
> This has caused me to encounter a problem where
> the gid I specified in the mounting parameters
> cannot apply to all files, as in the following
> situation:
>
> /data/tmp/events # mount | grep tracefs
> tracefs on /data/tmp type tracefs (rw,seclabel,relatime,gid=3012)
>
> gid 3012 = readtracefs
>
> /data/tmp # ls -lh
> total 0
> -r--r----- 1 root readtracefs 0 1970-01-01 08:00 README
> -r--r----- 1 root readtracefs 0 1970-01-01 08:00 available_events
>
> ums9621_1h10:/data/tmp/events # ls -lh
> total 0
> drwxr-xr-x 2 root root 0 2023-12-19 00:56 alarmtimer
> drwxr-xr-x 2 root root 0 2023-12-19 00:56 asoc
>
> It will prevent certain applications from accessing
> tracefs properly, I try to avoid this issue by making
> the following modifications.
>
> Signed-off-by: Dongliang Cui <[email protected]>


Thanks for the report, can you try this fix instead?

-- Steve

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 43e237864a42..2ccc849a5bda 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -148,7 +148,8 @@ static const struct file_operations eventfs_file_operations = {
.release = eventfs_release,
};

-static void update_inode_attr(struct inode *inode, struct eventfs_attr *attr, umode_t mode)
+static void update_inode_attr(struct dentry *dentry, struct inode *inode,
+ struct eventfs_attr *attr, umode_t mode)
{
if (!attr) {
inode->i_mode = mode;
@@ -162,9 +163,13 @@ static void update_inode_attr(struct inode *inode, struct eventfs_attr *attr, um

if (attr->mode & EVENTFS_SAVE_UID)
inode->i_uid = attr->uid;
+ else
+ inode->i_uid = d_inode(dentry->d_parent)->i_uid;

if (attr->mode & EVENTFS_SAVE_GID)
inode->i_gid = attr->gid;
+ else
+ inode->i_gid = d_inode(dentry->d_parent)->i_gid;
}

/**
@@ -206,7 +211,7 @@ static struct dentry *create_file(const char *name, umode_t mode,
return eventfs_failed_creating(dentry);

/* If the user updated the directory's attributes, use them */
- update_inode_attr(inode, attr, mode);
+ update_inode_attr(dentry, inode, attr, mode);

inode->i_op = &eventfs_file_inode_operations;
inode->i_fop = fop;
@@ -242,7 +247,8 @@ static struct dentry *create_dir(struct eventfs_inode *ei, struct dentry *parent
return eventfs_failed_creating(dentry);

/* If the user updated the directory's attributes, use them */
- update_inode_attr(inode, &ei->attr, S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO);
+ update_inode_attr(dentry, inode, &ei->attr,
+ S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO);

inode->i_op = &eventfs_root_dir_inode_operations;
inode->i_fop = &eventfs_file_operations;