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authorJan Kara <jack@suse.cz>2016-09-19 18:39:09 +0300
committerJan Kara <jack@suse.cz>2016-09-22 11:55:32 +0300
commit073931017b49d9458aa351605b43a7e34598caef (patch)
tree8c4374e82e5cad92bdb589e5be417f1a94870399 /fs/9p
parent5d3ddd84eaefffd23c028bce5610dac8726f71c1 (diff)
downloadlinux-073931017b49d9458aa351605b43a7e34598caef.tar.xz
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: Christoph Hellwig <hch@lst.de> Reviewed-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Diffstat (limited to 'fs/9p')
-rw-r--r--fs/9p/acl.c40
1 files changed, 17 insertions, 23 deletions
diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index 5b6a1743ea17..b3c2cc79c20d 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -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: