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Date: Wed, 15 Jul 2015 10:12:09 +0100
From: Luis Henriques <luis.henriques@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 134/185] proc: Allow creating permanently empty directories that serve as mount points
3.16.7-ckt15 -stable review patch. If anyone has any objections, please let me know.
------------------
From: "Eric W. Biederman" <ebiederm@...ssion.com>
commit eb6d38d5427b3ad42f5268da0f1dd31bb0af1264 upstream.
Add a new function proc_create_mount_point that when used to creates a
directory that can not be added to.
Add a new function is_empty_pde to test if a function is a mount
point.
Update the code to use make_empty_dir_inode when reporting
a permanently empty directory to the vfs.
Update the code to not allow adding to permanently empty directories.
Update /proc/openprom and /proc/fs/nfsd to be permanently empty directories.
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
fs/proc/generic.c | 24 ++++++++++++++++++++++++
fs/proc/inode.c | 4 ++++
fs/proc/internal.h | 6 ++++++
fs/proc/root.c | 4 ++--
4 files changed, 36 insertions(+), 2 deletions(-)
diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 2e2d9d5d78d9..c18d9b05cea9 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -334,6 +334,11 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
len = strlen(fn);
+ if (is_empty_pde(*parent)) {
+ WARN(1, "attempt to add to permanently empty directory");
+ return NULL;
+ }
+
ent = kzalloc(sizeof(struct proc_dir_entry) + len + 1, GFP_KERNEL);
if (!ent)
goto out;
@@ -409,6 +414,25 @@ struct proc_dir_entry *proc_mkdir(const char *name,
}
EXPORT_SYMBOL(proc_mkdir);
+struct proc_dir_entry *proc_create_mount_point(const char *name)
+{
+ umode_t mode = S_IFDIR | S_IRUGO | S_IXUGO;
+ struct proc_dir_entry *ent, *parent = NULL;
+
+ ent = __proc_create(&parent, name, mode, 2);
+ if (ent) {
+ ent->data = NULL;
+ ent->proc_fops = NULL;
+ ent->proc_iops = NULL;
+ if (proc_register(parent, ent) < 0) {
+ kfree(ent);
+ parent->nlink--;
+ ent = NULL;
+ }
+ }
+ return ent;
+}
+
struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
struct proc_dir_entry *parent,
const struct file_operations *proc_fops,
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 965b82e61570..6582583201ee 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -431,6 +431,10 @@ struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
PROC_I(inode)->pde = de;
+ if (is_empty_pde(de)) {
+ make_empty_dir_inode(inode);
+ return inode;
+ }
if (de->mode) {
inode->i_mode = de->mode;
inode->i_uid = de->uid;
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 8b24f3640cd9..e62c247b46cc 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -193,6 +193,12 @@ static inline struct proc_dir_entry *pde_get(struct proc_dir_entry *pde)
}
extern void pde_put(struct proc_dir_entry *);
+static inline bool is_empty_pde(const struct proc_dir_entry *pde)
+{
+ return S_ISDIR(pde->mode) && !pde->proc_iops;
+}
+struct proc_dir_entry *proc_create_mount_point(const char *name);
+
/*
* inode.c
*/
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 7fd8c1f1b1d9..dd77e1483196 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -176,10 +176,10 @@ void __init proc_root_init(void)
#endif
proc_mkdir("fs", NULL);
proc_mkdir("driver", NULL);
- proc_mkdir("fs/nfsd", NULL); /* somewhere for the nfsd filesystem to be mounted */
+ proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
#if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
/* just give it a mountpoint */
- proc_mkdir("openprom", NULL);
+ proc_create_mount_point("openprom");
#endif
proc_tty_init();
proc_mkdir("bus", NULL);
--
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