From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
First of all, calling pid_revalidate() in the end of <pid>/* lookups
is *not* about closing any kind of races; that used to be true once
upon a time, but these days those comments are actively misleading.
Especially since pid_revalidate() doesn't even do d_drop() on
failure anymore. It doesn't matter, anyway, since once
pid_revalidate() starts returning false, ->d_delete() of those
dentries starts saying "don't keep"; they won't get stuck in
dcache any longer than they are pinned.
These calls cannot be just removed, though - the side effect of
pid_revalidate() (updating i_uid/i_gid/etc.) is what we are calling
it for here.
Let's separate the "update ownership" into a new helper (pid_update_inode())
and use it, both in lookups and in pid_revalidate() itself.
The comments in pid_revalidate() are also out of date - they refer to
the time when pid_revalidate() used to call d_drop() directly...
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 55 +++++++++++++++++++++++-----------------------------
fs/proc/internal.h | 2 +-
fs/proc/namespaces.c | 9 +++------
3 files changed, 28 insertions(+), 38 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index eafa39a3a88c..6e0875505898 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1803,15 +1803,22 @@ int pid_getattr(const struct path *path, struct kstat *stat,
/* dentry stuff */
/*
- * Exceptional case: normally we are not allowed to unhash a busy
- * directory. In this case, however, we can do it - no aliasing problems
- * due to the way we treat inodes.
- *
+ * Set <pid>/... inode ownership (can change due to setuid(), etc.)
+ */
+void pid_update_inode(struct task_struct *task, struct inode *inode)
+{
+ task_dump_owner(task, inode->i_mode, &inode->i_uid, &inode->i_gid);
+
+ inode->i_mode &= ~(S_ISUID | S_ISGID);
+ security_task_to_inode(task, inode);
+}
+
+/*
* Rewrite the inode's ownerships here because the owning task may have
* performed a setuid(), etc.
*
*/
-int pid_revalidate(struct dentry *dentry, unsigned int flags)
+static int pid_revalidate(struct dentry *dentry, unsigned int flags)
{
struct inode *inode;
struct task_struct *task;
@@ -1823,10 +1830,7 @@ int pid_revalidate(struct dentry *dentry, unsigned int flags)
task = get_proc_task(inode);
if (task) {
- task_dump_owner(task, inode->i_mode, &inode->i_uid, &inode->i_gid);
-
- inode->i_mode &= ~(S_ISUID | S_ISGID);
- security_task_to_inode(task, inode);
+ pid_update_inode(task, inode);
put_task_struct(task);
return 1;
}
@@ -2438,7 +2442,7 @@ static int proc_pident_instantiate(struct inode *dir,
inode = proc_pid_make_inode(dir->i_sb, task, p->mode);
if (!inode)
- goto out;
+ return -ENOENT;
ei = PROC_I(inode);
if (S_ISDIR(inode->i_mode))
@@ -2448,13 +2452,10 @@ static int proc_pident_instantiate(struct inode *dir,
if (p->fop)
inode->i_fop = p->fop;
ei->op = p->op;
+ pid_update_inode(task, inode);
d_set_d_op(dentry, &pid_dentry_operations);
d_add(dentry, inode);
- /* Close the race of the process dying before we return the dentry */
- if (pid_revalidate(dentry, 0))
- return 0;
-out:
- return -ENOENT;
+ return 0;
}
static struct dentry *proc_pident_lookup(struct inode *dir,
@@ -3140,22 +3141,18 @@ static int proc_pid_instantiate(struct inode *dir,
inode = proc_pid_make_inode(dir->i_sb, task, S_IFDIR | S_IRUGO | S_IXUGO);
if (!inode)
- goto out;
+ return -ENOENT;
inode->i_op = &proc_tgid_base_inode_operations;
inode->i_fop = &proc_tgid_base_operations;
inode->i_flags|=S_IMMUTABLE;
set_nlink(inode, nlink_tgid);
+ pid_update_inode(task, inode);
d_set_d_op(dentry, &pid_dentry_operations);
-
d_add(dentry, inode);
- /* Close the race of the process dying before we return the dentry */
- if (pid_revalidate(dentry, 0))
- return 0;
-out:
- return -ENOENT;
+ return 0;
}
struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags)
@@ -3434,23 +3431,19 @@ static int proc_task_instantiate(struct inode *dir,
{
struct inode *inode;
inode = proc_pid_make_inode(dir->i_sb, task, S_IFDIR | S_IRUGO | S_IXUGO);
-
if (!inode)
- goto out;
+ return -ENOENT;
+
inode->i_op = &proc_tid_base_inode_operations;
inode->i_fop = &proc_tid_base_operations;
- inode->i_flags|=S_IMMUTABLE;
+ inode->i_flags |= S_IMMUTABLE;
set_nlink(inode, nlink_tid);
+ pid_update_inode(task, inode);
d_set_d_op(dentry, &pid_dentry_operations);
-
d_add(dentry, inode);
- /* Close the race of the process dying before we return the dentry */
- if (pid_revalidate(dentry, 0))
- return 0;
-out:
- return -ENOENT;
+ return 0;
}
static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags)
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 0f1692e63cb6..04a455b9ae69 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -147,7 +147,7 @@ extern const struct dentry_operations pid_dentry_operations;
extern int pid_getattr(const struct path *, struct kstat *, u32, unsigned int);
extern int proc_setattr(struct dentry *, struct iattr *);
extern struct inode *proc_pid_make_inode(struct super_block *, struct task_struct *, umode_t);
-extern int pid_revalidate(struct dentry *, unsigned int);
+extern void pid_update_inode(struct task_struct *, struct inode *);
extern int pid_delete_dentry(const struct dentry *);
extern int proc_pid_readdir(struct file *, struct dir_context *);
extern struct dentry *proc_pid_lookup(struct inode *, struct dentry *, unsigned int);
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index 59b17e509f46..ad1adce6541d 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -96,19 +96,16 @@ static int proc_ns_instantiate(struct inode *dir,
inode = proc_pid_make_inode(dir->i_sb, task, S_IFLNK | S_IRWXUGO);
if (!inode)
- goto out;
+ return -ENOENT;
ei = PROC_I(inode);
inode->i_op = &proc_ns_link_inode_operations;
ei->ns_ops = ns_ops;
+ pid_update_inode(task, inode);
d_set_d_op(dentry, &pid_dentry_operations);
d_add(dentry, inode);
- /* Close the race of the process dying before we return the dentry */
- if (pid_revalidate(dentry, 0))
- return 0;
-out:
- return -ENOENT;
+ return 0;
}
static int proc_ns_dir_readdir(struct file *file, struct dir_context *ctx)
--
2.11.0
