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Subject[PATCH v6 09/10] proc: add option to mount only a pids subset
Date
This allows to hide all files and directories in the procfs that are not
related to tasks.

Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
---
fs/proc/generic.c | 20 ++++++++++++++++++++
fs/proc/inode.c | 8 ++++++++
fs/proc/root.c | 14 ++++++++++++++
include/linux/proc_fs.h | 26 ++++++++++++++++++++++++++
4 files changed, 68 insertions(+)

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 64e9ee1b129e..2fa919a5544d 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -267,6 +267,11 @@ struct dentry *proc_lookup_de(struct inode *dir, struct dentry *dentry,
struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
+ struct proc_fs_info *fs_info = proc_sb_info(dir->i_sb);
+
+ if (proc_fs_pidonly(fs_info) == PROC_PIDONLY_ON)
+ return ERR_PTR(-ENOENT);
+
return proc_lookup_de(dir, dentry, PDE(dir));
}

@@ -323,10 +328,24 @@ int proc_readdir_de(struct file *file, struct dir_context *ctx,
int proc_readdir(struct file *file, struct dir_context *ctx)
{
struct inode *inode = file_inode(file);
+ struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
+
+ if (proc_fs_pidonly(fs_info) == PROC_PIDONLY_ON)
+ return 1;

return proc_readdir_de(file, ctx, PDE(inode));
}

+static int proc_dir_open(struct inode *inode, struct file *file)
+{
+ struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
+
+ if (proc_fs_pidonly(fs_info) == PROC_PIDONLY_ON)
+ return -ENOENT;
+
+ return 0;
+}
+
/*
* These are the generic /proc directory operations. They
* use the in-memory "struct proc_dir_entry" tree to parse
@@ -336,6 +355,7 @@ static const struct file_operations proc_dir_operations = {
.llseek = generic_file_llseek,
.read = generic_read_dir,
.iterate_shared = proc_readdir,
+ .open = proc_dir_open,
};

/*
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 70b722fb8811..fe9d20da3862 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -107,6 +107,7 @@ static int proc_show_options(struct seq_file *seq, struct dentry *root)
struct proc_fs_info *fs_info = proc_sb_info(root->d_sb);
int hidepid = proc_fs_hide_pid(fs_info);
kgid_t gid = proc_fs_pid_gid(fs_info);
+ int pidonly = proc_fs_pidonly(fs_info);

if (!gid_eq(gid, GLOBAL_ROOT_GID))
seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, gid));
@@ -114,6 +115,9 @@ static int proc_show_options(struct seq_file *seq, struct dentry *root)
if (hidepid != HIDEPID_OFF)
seq_printf(seq, ",hidepid=%u", hidepid);

+ if (pidonly != PROC_PIDONLY_OFF)
+ seq_printf(seq, ",pidonly=%u", pidonly);
+
return 0;
}

@@ -333,12 +337,16 @@ proc_reg_get_unmapped_area(struct file *file, unsigned long orig_addr,

static int proc_reg_open(struct inode *inode, struct file *file)
{
+ struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
struct proc_dir_entry *pde = PDE(inode);
int rv = 0;
typeof_member(struct file_operations, open) open;
typeof_member(struct file_operations, release) release;
struct pde_opener *pdeo;

+ if (proc_fs_pidonly(fs_info) == PROC_PIDONLY_ON)
+ return -ENOENT;
+
/*
* Ensure that
* 1) PDE's ->release hook will be called no matter what
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 3c7b29140293..fc26c22a5906 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -34,16 +34,19 @@ struct proc_fs_context {
unsigned int mask;
int hidepid;
int gid;
+ int pidonly;
};

enum proc_param {
Opt_gid,
Opt_hidepid,
+ Opt_pidonly,
};

static const struct fs_parameter_spec proc_param_specs[] = {
fsparam_u32("gid", Opt_gid),
fsparam_u32("hidepid", Opt_hidepid),
+ fsparam_u32("pidonly", Opt_pidonly),
{}
};

@@ -74,6 +77,13 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
return invalf(fc, "proc: hidepid value must be between 0 and 3.\n");
break;

+ case Opt_pidonly:
+ ctx->pidonly = result.uint_32;
+ if (ctx->pidonly < PROC_PIDONLY_OFF ||
+ ctx->pidonly > PROC_PIDONLY_ON)
+ return invalf(fc, "proc: pidonly value must be 0 or 1.\n");
+ break;
+
default:
return -EINVAL;
}
@@ -94,6 +104,7 @@ static void proc_apply_options(struct proc_fs_info *fs_info,

proc_fs_set_pid_gid(fs_info, proc_fs_pid_gid(pidns_fs_info));
proc_fs_set_hide_pid(fs_info, proc_fs_hide_pid(pidns_fs_info));
+ proc_fs_set_pidonly(fs_info, proc_fs_pidonly(pidns_fs_info));
}

if (ctx->mask & (1 << Opt_gid))
@@ -101,6 +112,9 @@ static void proc_apply_options(struct proc_fs_info *fs_info,

if (ctx->mask & (1 << Opt_hidepid))
proc_fs_set_hide_pid(fs_info, ctx->hidepid);
+
+ if (ctx->mask & (1 << Opt_pidonly))
+ proc_fs_set_pidonly(fs_info, ctx->pidonly);
}

static int proc_fill_super(struct super_block *s, struct fs_context *fc)
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 83c87ea65505..ef1c0d9712b0 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -20,6 +20,12 @@ enum {
HIDEPID_NOT_PTRACABLE = 3, /* Limit pids to only ptracable pids */
};

+/* definitions for proc mount option pidonly */
+enum {
+ PROC_PIDONLY_OFF = 0,
+ PROC_PIDONLY_ON = 1,
+};
+
struct proc_fs_info {
struct list_head pidns_entry; /* Node in procfs_mounts of a pidns */
struct super_block *m_super;
@@ -28,6 +34,7 @@ struct proc_fs_info {
struct dentry *proc_thread_self; /* For /proc/thread-self */
kgid_t pid_gid;
int hide_pid;
+ int pidonly;
};

#ifdef CONFIG_PROC_FS
@@ -39,6 +46,11 @@ static inline struct proc_fs_info *proc_sb_info(struct super_block *sb)
return sb->s_fs_info;
}

+static inline void proc_fs_set_pidonly(struct proc_fs_info *fs_info, int value)
+{
+ fs_info->pidonly = value;
+}
+
static inline void proc_fs_set_hide_pid(struct proc_fs_info *fs_info, int hide_pid)
{
fs_info->hide_pid = hide_pid;
@@ -49,6 +61,11 @@ static inline void proc_fs_set_pid_gid(struct proc_fs_info *fs_info, kgid_t gid)
fs_info->pid_gid = gid;
}

+static inline int proc_fs_pidonly(struct proc_fs_info *fs_info)
+{
+ return fs_info->pidonly;
+}
+
static inline int proc_fs_hide_pid(struct proc_fs_info *fs_info)
{
return fs_info->hide_pid;
@@ -134,6 +151,10 @@ static inline struct proc_fs_info *proc_sb_info(struct super_block *sb)
return NULL;
}

+static inline void proc_fs_set_pidonly(struct proc_fs_info *fs_info, int value)
+{
+}
+
static inline void proc_fs_set_hide_pid(struct proc_fs_info *fs_info, int hide_pid)
{
}
@@ -142,6 +163,11 @@ static inline void proc_fs_set_pid_gid(struct proc_info_fs *fs_info, kgid_t gid)
{
}

+static inline void proc_fs_pidonly(struct proc_fs_info *fs_info)
+{
+ return PROC_PIDONLY_OFF;
+}
+
static inline int proc_fs_hide_pid(struct proc_fs_info *fs_info)
{
return 0;
--
2.24.1
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