Commit 07393101 authored by Jan Kara's avatar Jan Kara

posix_acl: Clear SGID bit when setting file permissions

When file permissions are modified via chmod(2) and the user is not in
the owning group or capable of CAP_FSETID, the setgid bit is cleared in
inode_change_ok().  Setting a POSIX ACL via setxattr(2) sets the file
permissions as well as the new ACL, but doesn't clear the setgid bit in
a similar way; this allows to bypass the check in chmod(2).  Fix that.

References: CVE-2016-7097
Reviewed-by: 's avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: 's avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: 's avatarJan Kara <jack@suse.cz>
Signed-off-by: 's avatarAndreas Gruenbacher <agruenba@redhat.com>
parent 5d3ddd84
......@@ -276,32 +276,26 @@ static int v9fs_xattr_set_acl(const struct xattr_handler *handler,
switch (handler->flags) {
case ACL_TYPE_ACCESS:
if (acl) {
umode_t mode = inode->i_mode;
retval = posix_acl_equiv_mode(acl, &mode);
if (retval < 0)
struct iattr iattr;
retval = posix_acl_update_mode(inode, &iattr.ia_mode, &acl);
if (retval)
goto err_out;
else {
struct iattr iattr;
if (retval == 0) {
/*
* ACL can be represented
* by the mode bits. So don't
* update ACL.
*/
acl = NULL;
value = NULL;
size = 0;
}
/* Updte the mode bits */
iattr.ia_mode = ((mode & S_IALLUGO) |
(inode->i_mode & ~S_IALLUGO));
iattr.ia_valid = ATTR_MODE;
/* FIXME should we update ctime ?
* What is the following setxattr update the
* mode ?
if (!acl) {
/*
* ACL can be represented
* by the mode bits. So don't
* update ACL.
*/
v9fs_vfs_setattr_dotl(dentry, &iattr);
value = NULL;
size = 0;
}
iattr.ia_valid = ATTR_MODE;
/* FIXME should we update ctime ?
* What is the following setxattr update the
* mode ?
*/
v9fs_vfs_setattr_dotl(dentry, &iattr);
}
break;
case ACL_TYPE_DEFAULT:
......
......@@ -79,11 +79,9 @@ static int __btrfs_set_acl(struct btrfs_trans_handle *trans,
case ACL_TYPE_ACCESS:
name = XATTR_NAME_POSIX_ACL_ACCESS;
if (acl) {
ret = posix_acl_equiv_mode(acl, &inode->i_mode);
if (ret < 0)
ret = posix_acl_update_mode(inode, &inode->i_mode, &acl);
if (ret)
return ret;
if (ret == 0)
acl = NULL;
}
ret = 0;
break;
......
......@@ -95,11 +95,9 @@ int ceph_set_acl(struct inode *inode, struct posix_acl *acl, int type)
case ACL_TYPE_ACCESS:
name = XATTR_NAME_POSIX_ACL_ACCESS;
if (acl) {
ret = posix_acl_equiv_mode(acl, &new_mode);
if (ret < 0)
ret = posix_acl_update_mode(inode, &new_mode, &acl);
if (ret)
goto out;
if (ret == 0)
acl = NULL;
}
break;
case ACL_TYPE_DEFAULT:
......
......@@ -190,15 +190,11 @@ ext2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
case ACL_TYPE_ACCESS:
name_index = EXT2_XATTR_INDEX_POSIX_ACL_ACCESS;
if (acl) {
error = posix_acl_equiv_mode(acl, &inode->i_mode);
if (error < 0)
error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
if (error)
return error;
else {
inode->i_ctime = CURRENT_TIME_SEC;
mark_inode_dirty(inode);
if (error == 0)
acl = NULL;
}
inode->i_ctime = CURRENT_TIME_SEC;
mark_inode_dirty(inode);
}
break;
......
......@@ -193,15 +193,11 @@ __ext4_set_acl(handle_t *handle, struct inode *inode, int type,
case ACL_TYPE_ACCESS:
name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS;
if (acl) {
error = posix_acl_equiv_mode(acl, &inode->i_mode);
if (error < 0)
error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
if (error)
return error;
else {
inode->i_ctime = ext4_current_time(inode);
ext4_mark_inode_dirty(handle, inode);
if (error == 0)
acl = NULL;
}
inode->i_ctime = ext4_current_time(inode);
ext4_mark_inode_dirty(handle, inode);
}
break;
......
......@@ -210,12 +210,10 @@ static int __f2fs_set_acl(struct inode *inode, int type,
case ACL_TYPE_ACCESS:
name_index = F2FS_XATTR_INDEX_POSIX_ACL_ACCESS;
if (acl) {
error = posix_acl_equiv_mode(acl, &inode->i_mode);
if (error < 0)
error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
if (error)
return error;
set_acl_inode(inode, inode->i_mode);
if (error == 0)
acl = NULL;
}
break;
......
......@@ -92,17 +92,11 @@ int __gfs2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
if (type == ACL_TYPE_ACCESS) {
umode_t mode = inode->i_mode;
error = posix_acl_equiv_mode(acl, &mode);
if (error < 0)
error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
if (error)
return error;
if (error == 0)
acl = NULL;
if (mode != inode->i_mode) {
inode->i_mode = mode;
if (mode != inode->i_mode)
mark_inode_dirty(inode);
}
}
if (acl) {
......
......@@ -65,8 +65,8 @@ int hfsplus_set_posix_acl(struct inode *inode, struct posix_acl *acl,
case ACL_TYPE_ACCESS:
xattr_name = XATTR_NAME_POSIX_ACL_ACCESS;
if (acl) {
err = posix_acl_equiv_mode(acl, &inode->i_mode);
if (err < 0)
err = posix_acl_update_mode(inode, &inode->i_mode, &acl);
if (err)
return err;
}
err = 0;
......
......@@ -233,9 +233,10 @@ int jffs2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
case ACL_TYPE_ACCESS:
xprefix = JFFS2_XPREFIX_ACL_ACCESS;
if (acl) {
umode_t mode = inode->i_mode;
rc = posix_acl_equiv_mode(acl, &mode);
if (rc < 0)
umode_t mode;
rc = posix_acl_update_mode(inode, &mode, &acl);
if (rc)
return rc;
if (inode->i_mode != mode) {
struct iattr attr;
......@@ -247,8 +248,6 @@ int jffs2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
if (rc < 0)
return rc;
}
if (rc == 0)
acl = NULL;
}
break;
case ACL_TYPE_DEFAULT:
......
......@@ -78,13 +78,11 @@ static int __jfs_set_acl(tid_t tid, struct inode *inode, int type,
case ACL_TYPE_ACCESS:
ea_name = XATTR_NAME_POSIX_ACL_ACCESS;
if (acl) {
rc = posix_acl_equiv_mode(acl, &inode->i_mode);
if (rc < 0)
rc = posix_acl_update_mode(inode, &inode->i_mode, &acl);
if (rc)
return rc;
inode->i_ctime = CURRENT_TIME;
mark_inode_dirty(inode);
if (rc == 0)
acl = NULL;
}
break;
case ACL_TYPE_DEFAULT:
......
......@@ -241,13 +241,11 @@ int ocfs2_set_acl(handle_t *handle,
case ACL_TYPE_ACCESS:
name_index = OCFS2_XATTR_INDEX_POSIX_ACL_ACCESS;
if (acl) {
umode_t mode = inode->i_mode;
ret = posix_acl_equiv_mode(acl, &mode);
if (ret < 0)
return ret;
umode_t mode;
if (ret == 0)
acl = NULL;
ret = posix_acl_update_mode(inode, &mode, &acl);
if (ret)
return ret;
ret = ocfs2_acl_set_mode(inode, di_bh,
handle, mode);
......
......@@ -73,14 +73,11 @@ int orangefs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
case ACL_TYPE_ACCESS:
name = XATTR_NAME_POSIX_ACL_ACCESS;
if (acl) {
umode_t mode = inode->i_mode;
/*
* can we represent this with the traditional file
* mode permission bits?
*/
error = posix_acl_equiv_mode(acl, &mode);
if (error < 0) {
gossip_err("%s: posix_acl_equiv_mode err: %d\n",
umode_t mode;
error = posix_acl_update_mode(inode, &mode, &acl);
if (error) {
gossip_err("%s: posix_acl_update_mode err: %d\n",
__func__,
error);
return error;
......@@ -90,8 +87,6 @@ int orangefs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
SetModeFlag(orangefs_inode);
inode->i_mode = mode;
mark_inode_dirty_sync(inode);
if (error == 0)
acl = NULL;
}
break;
case ACL_TYPE_DEFAULT:
......
......@@ -626,6 +626,37 @@ posix_acl_create(struct inode *dir, umode_t *mode,
}
EXPORT_SYMBOL_GPL(posix_acl_create);
/**
* posix_acl_update_mode - update mode in set_acl
*
* Update the file mode when setting an ACL: compute the new file permission
* bits based on the ACL. In addition, if the ACL is equivalent to the new
* file mode, set *acl to NULL to indicate that no ACL should be set.
*
* As with chmod, clear the setgit bit if the caller is not in the owning group
* or capable of CAP_FSETID (see inode_change_ok).
*
* Called from set_acl inode operations.
*/
int posix_acl_update_mode(struct inode *inode, umode_t *mode_p,
struct posix_acl **acl)
{
umode_t mode = inode->i_mode;
int error;
error = posix_acl_equiv_mode(*acl, &mode);
if (error < 0)
return error;
if (error == 0)
*acl = NULL;
if (!in_group_p(inode->i_gid) &&
!capable_wrt_inode_uidgid(inode, CAP_FSETID))
mode &= ~S_ISGID;
*mode_p = mode;
return 0;
}
EXPORT_SYMBOL(posix_acl_update_mode);
/*
* Fix up the uids and gids in posix acl extended attributes in place.
*/
......
......@@ -242,13 +242,9 @@ __reiserfs_set_acl(struct reiserfs_transaction_handle *th, struct inode *inode,
case ACL_TYPE_ACCESS:
name = XATTR_NAME_POSIX_ACL_ACCESS;
if (acl) {
error = posix_acl_equiv_mode(acl, &inode->i_mode);
if (error < 0)
error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
if (error)
return error;
else {
if (error == 0)
acl = NULL;
}
}
break;
case ACL_TYPE_DEFAULT:
......
......@@ -257,16 +257,11 @@ xfs_set_acl(struct inode *inode, struct posix_acl *acl, int type)
return error;
if (type == ACL_TYPE_ACCESS) {
umode_t mode = inode->i_mode;
error = posix_acl_equiv_mode(acl, &mode);
if (error <= 0) {
acl = NULL;
if (error < 0)
return error;
}
umode_t mode;
error = posix_acl_update_mode(inode, &mode, &acl);
if (error)
return error;
error = xfs_set_mode(inode, mode);
if (error)
return error;
......
......@@ -93,6 +93,7 @@ extern int set_posix_acl(struct inode *, int, struct posix_acl *);
extern int posix_acl_chmod(struct inode *, umode_t);
extern int posix_acl_create(struct inode *, umode_t *, struct posix_acl **,
struct posix_acl **);
extern int posix_acl_update_mode(struct inode *, umode_t *, struct posix_acl **);
extern int simple_set_acl(struct inode *, struct posix_acl *, int);
extern int simple_acl_create(struct inode *, struct inode *);
......
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