From 01de85e057328ecbef36e108673b1e81059d54c1 Mon Sep 17 00:00:00 2001
From: Jens Axboe <jens.axboe@oracle.com>
Date: Tue, 17 Oct 2006 19:50:36 +0200
Subject: [PATCH] [PATCH] Add lockless helpers for remove_suid()
Right now users have to grab i_mutex before calling remove_suid(), in the
unlikely event that a call to ->setattr() may be needed. Split up the
function in two parts:
- One to check if we need to remove suid
- One to actually remove it
The first we can call lockless.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
include/linux/fs.h | 2 ++
mm/filemap.c | 30 ++++++++++++++++++++++--------
2 files changed, 24 insertions(+), 8 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d695ba2346a30..2fe6e3f900ba5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1712,6 +1712,8 @@ extern void __iget(struct inode * inode);
extern void clear_inode(struct inode *);
extern void destroy_inode(struct inode *);
extern struct inode *new_inode(struct super_block *);
+extern int __remove_suid(struct dentry *, int);
+extern int should_remove_suid(struct dentry *);
extern int remove_suid(struct dentry *);
extern void remove_dquot_ref(struct super_block *, int, struct list_head *);
diff --git a/mm/filemap.c b/mm/filemap.c
index 3464b681f8449..7c7addb9333c8 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1884,11 +1884,10 @@ __grab_cache_page(struct address_space *mapping, unsigned long index,
* if suid or (sgid and xgrp)
* remove privs
*/
-int remove_suid(struct dentry *dentry)
+int should_remove_suid(struct dentry *dentry)
{
mode_t mode = dentry->d_inode->i_mode;
int kill = 0;
- int result = 0;
/* suid always must be killed */
if (unlikely(mode & S_ISUID))
@@ -1901,13 +1900,28 @@ int remove_suid(struct dentry *dentry)
if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
kill |= ATTR_KILL_SGID;
- if (unlikely(kill && !capable(CAP_FSETID))) {
- struct iattr newattrs;
+ if (unlikely(kill && !capable(CAP_FSETID)))
+ return kill;
- newattrs.ia_valid = ATTR_FORCE | kill;
- result = notify_change(dentry, &newattrs);
- }
- return result;
+ return 0;
+}
+
+int __remove_suid(struct dentry *dentry, int kill)
+{
+ struct iattr newattrs;
+
+ newattrs.ia_valid = ATTR_FORCE | kill;
+ return notify_change(dentry, &newattrs);
+}
+
+int remove_suid(struct dentry *dentry)
+{
+ int kill = should_remove_suid(dentry);
+
+ if (unlikely(kill))
+ return __remove_suid(dentry, kill);
+
+ return 0;
}
EXPORT_SYMBOL(remove_suid);
--
GitLab