Commit 01de85e0 authored by Jens Axboe's avatar Jens Axboe Committed by Jens Axboe
Browse files

[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: default avatarJens Axboe <jens.axboe@oracle.com>
parent 6da61809

include/linux/fs.h

+2 −0
Original line number Diff line number Diff line
@@ -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 *);

mm/filemap.c

+22 −8
Original line number Diff line number Diff line
@@ -1884,11 +1884,10 @@ repeat: 
 *	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))) {

	if (unlikely(kill && !capable(CAP_FSETID)))

		return kill;



	return 0;

}



int __remove_suid(struct dentry *dentry, int kill)

{

	struct iattr newattrs;



	newattrs.ia_valid = ATTR_FORCE | kill;

		result = notify_change(dentry, &newattrs);

	return notify_change(dentry, &newattrs);

}

	return result;



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);

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