From 073931017b49d9458aa351605b43a7e34598caef Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Mon, 19 Sep 2016 17:39:09 +0200 Subject: [PATCH] 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 Reviewed-by: Jeff Layton Signed-off-by: Jan Kara Signed-off-by: Andreas Gruenbacher --- fs/9p/acl.c | 40 +++++++++++++++++---------------------- fs/btrfs/acl.c | 6 ++---- fs/ceph/acl.c | 6 ++---- fs/ext2/acl.c | 12 ++++-------- fs/ext4/acl.c | 12 ++++-------- fs/f2fs/acl.c | 6 ++---- fs/gfs2/acl.c | 12 +++--------- fs/hfsplus/posix_acl.c | 4 ++-- fs/jffs2/acl.c | 9 ++++----- fs/jfs/acl.c | 6 ++---- fs/ocfs2/acl.c | 10 ++++------ fs/orangefs/acl.c | 15 +++++---------- fs/posix_acl.c | 31 ++++++++++++++++++++++++++++++ fs/reiserfs/xattr_acl.c | 8 ++------ fs/xfs/xfs_acl.c | 13 ++++--------- include/linux/posix_acl.h | 1 + 16 files changed, 89 insertions(+), 102 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: diff --git a/fs/btrfs/acl.c b/fs/btrfs/acl.c index 53bb7af4e5f0..247b8dfaf6e5 100644 --- a/fs/btrfs/acl.c +++ b/fs/btrfs/acl.c @@ -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; diff --git a/fs/ceph/acl.c b/fs/ceph/acl.c index 4f67227f69a5..d0b6b342dff9 100644 --- a/fs/ceph/acl.c +++ b/fs/ceph/acl.c @@ -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: diff --git a/fs/ext2/acl.c b/fs/ext2/acl.c index 42f1d1814083..e725aa0890e0 100644 --- a/fs/ext2/acl.c +++ b/fs/ext2/acl.c @@ -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; diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c index c6601a476c02..dfa519979038 100644 --- a/fs/ext4/acl.c +++ b/fs/ext4/acl.c @@ -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; diff --git a/fs/f2fs/acl.c b/fs/f2fs/acl.c index 4dcc9e28dc5c..31344247ce89 100644 --- a/fs/f2fs/acl.c +++ b/fs/f2fs/acl.c @@ -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; diff --git a/fs/gfs2/acl.c b/fs/gfs2/acl.c index 363ba9e9d8d0..2524807ee070 100644 --- a/fs/gfs2/acl.c +++ b/fs/gfs2/acl.c @@ -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) { diff --git a/fs/hfsplus/posix_acl.c b/fs/hfsplus/posix_acl.c index ab7ea2506b4d..9b92058a1240 100644 --- a/fs/hfsplus/posix_acl.c +++ b/fs/hfsplus/posix_acl.c @@ -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; diff --git a/fs/jffs2/acl.c b/fs/jffs2/acl.c index bc2693d56298..2a0f2a1044c1 100644 --- a/fs/jffs2/acl.c +++ b/fs/jffs2/acl.c @@ -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: diff --git a/fs/jfs/acl.c b/fs/jfs/acl.c index 21fa92ba2c19..3a1e1554a4e3 100644 --- a/fs/jfs/acl.c +++ b/fs/jfs/acl.c @@ -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: diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c index 2162434728c0..164307b99405 100644 --- a/fs/ocfs2/acl.c +++ b/fs/ocfs2/acl.c @@ -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); diff --git a/fs/orangefs/acl.c b/fs/orangefs/acl.c index 28f2195cd798..7a3754488312 100644 --- a/fs/orangefs/acl.c +++ b/fs/orangefs/acl.c @@ -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: diff --git a/fs/posix_acl.c b/fs/posix_acl.c index 59d47ab0791a..bfc3ec388322 100644 --- a/fs/posix_acl.c +++ b/fs/posix_acl.c @@ -626,6 +626,37 @@ no_mem: } 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 dbed42f755e0..27376681c640 100644 --- a/fs/reiserfs/xattr_acl.c +++ b/fs/reiserfs/xattr_acl.c @@ -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: diff --git a/fs/xfs/xfs_acl.c b/fs/xfs/xfs_acl.c index b6e527b8eccb..8a0dec89ca56 100644 --- a/fs/xfs/xfs_acl.c +++ b/fs/xfs/xfs_acl.c @@ -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; diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h index d5d3d741f028..bf1046d0397b 100644 --- a/include/linux/posix_acl.h +++ b/include/linux/posix_acl.h @@ -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 *);