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>
diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index 5b6a174..b3c2cc7 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -276,32 +276,26 @@
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:
diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c
index 53bb7af..247b8df 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -79,11 +79,9 @@
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;
diff --git a/fs/ceph/acl.c b/fs/ceph/acl.c
index 4f67227..d0b6b342 100644
--- a/fs/ceph/acl.c
+++ b/fs/ceph/acl.c
@@ -95,11 +95,9 @@
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:
diff --git a/fs/ext2/acl.c b/fs/ext2/acl.c
index 42f1d18..e725aa0 100644
--- a/fs/ext2/acl.c
+++ b/fs/ext2/acl.c
@@ -190,15 +190,11 @@
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;
diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
index c6601a4..dfa5199 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -193,15 +193,11 @@
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;
diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c
index 4dcc9e2..3134424 100644
--- a/fs/f2fs/acl.c
+++ b/fs/f2fs/acl.c
@@ -210,12 +210,10 @@
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;
diff --git a/fs/gfs2/acl.c b/fs/gfs2/acl.c
index 363ba9e..2524807 100644
--- a/fs/gfs2/acl.c
+++ b/fs/gfs2/acl.c
@@ -92,17 +92,11 @@
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) {
diff --git a/fs/hfsplus/posix_acl.c b/fs/hfsplus/posix_acl.c
index ab7ea2506..9b92058 100644
--- a/fs/hfsplus/posix_acl.c
+++ b/fs/hfsplus/posix_acl.c
@@ -65,8 +65,8 @@
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;
diff --git a/fs/jffs2/acl.c b/fs/jffs2/acl.c
index bc2693d..2a0f2a1 100644
--- a/fs/jffs2/acl.c
+++ b/fs/jffs2/acl.c
@@ -233,9 +233,10 @@
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 @@
if (rc < 0)
return rc;
}
- if (rc == 0)
- acl = NULL;
}
break;
case ACL_TYPE_DEFAULT:
diff --git a/fs/jfs/acl.c b/fs/jfs/acl.c
index 21fa92b..3a1e155 100644
--- a/fs/jfs/acl.c
+++ b/fs/jfs/acl.c
@@ -78,13 +78,11 @@
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:
diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
index 2162434..164307b 100644
--- a/fs/ocfs2/acl.c
+++ b/fs/ocfs2/acl.c
@@ -241,13 +241,11 @@
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);
diff --git a/fs/orangefs/acl.c b/fs/orangefs/acl.c
index 28f2195..7a37544 100644
--- a/fs/orangefs/acl.c
+++ b/fs/orangefs/acl.c
@@ -73,14 +73,11 @@
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 @@
SetModeFlag(orangefs_inode);
inode->i_mode = mode;
mark_inode_dirty_sync(inode);
- if (error == 0)
- acl = NULL;
}
break;
case ACL_TYPE_DEFAULT:
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 59d47ab0..bfc3ec3 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -626,6 +626,37 @@
}
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.
*/
diff --git a/fs/reiserfs/xattr_acl.c b/fs/reiserfs/xattr_acl.c
index dbed42f..2737668 100644
--- a/fs/reiserfs/xattr_acl.c
+++ b/fs/reiserfs/xattr_acl.c
@@ -242,13 +242,9 @@
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:
diff --git a/fs/xfs/xfs_acl.c b/fs/xfs/xfs_acl.c
index b6e527b..8a0dec8 100644
--- a/fs/xfs/xfs_acl.c
+++ b/fs/xfs/xfs_acl.c
@@ -257,16 +257,11 @@
return error;
if (type == ACL_TYPE_ACCESS) {
- umode_t mode = inode->i_mode;
- error = posix_acl_equiv_mode(acl, &mode);
+ umode_t mode;
- if (error <= 0) {
- acl = NULL;
-
- if (error < 0)
- return error;
- }
-
+ error = posix_acl_update_mode(inode, &mode, &acl);
+ if (error)
+ return error;
error = xfs_set_mode(inode, mode);
if (error)
return error;
diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
index d5d3d74..bf1046d 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -93,6 +93,7 @@
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 *);
