[for-3.18,4/7] posix_acl: Clear SGID bit when setting file permissions

Message ID 1493832958-12489-5-git-send-email-amit.pundir@linaro.org
State New
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Series
  • Security fixes picked from android security bulletins
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Commit Message

Amit Pundir May 3, 2017, 5:35 p.m.
From: Jan Kara <jack@suse.cz>


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>

(cherry picked from commit 073931017b49d9458aa351605b43a7e34598caef)
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>

---
 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            | 20 ++++++++------------
 fs/posix_acl.c            | 31 +++++++++++++++++++++++++++++++
 fs/reiserfs/xattr_acl.c   |  8 ++------
 fs/xfs/xfs_acl.c          | 13 ++++---------
 include/linux/posix_acl.h |  1 +
 15 files changed, 88 insertions(+), 98 deletions(-)

-- 
2.7.4

Patch

diff --git a/fs/9p/acl.c b/fs/9p/acl.c
index 8482f2d11606..d3f5d487ae46 100644
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -320,32 +320,26 @@  static int v9fs_xattr_set_acl(struct dentry *dentry, const char *name,
 	case ACL_TYPE_ACCESS:
 		name = POSIX_ACL_XATTR_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 9a0124a95851..fb3e64d37cb4 100644
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -83,11 +83,9 @@  static int __btrfs_set_acl(struct btrfs_trans_handle *trans,
 	case ACL_TYPE_ACCESS:
 		name = POSIX_ACL_XATTR_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 5bd853ba44ff..6a4a3e2a46cf 100644
--- a/fs/ceph/acl.c
+++ b/fs/ceph/acl.c
@@ -108,11 +108,9 @@  int ceph_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 	case ACL_TYPE_ACCESS:
 		name = POSIX_ACL_XATTR_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 27695e6f4e46..d6aeb84e90b6 100644
--- a/fs/ext2/acl.c
+++ b/fs/ext2/acl.c
@@ -193,15 +193,11 @@  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 d40c8dbbb0d6..87d9bbf6a53f 100644
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -201,15 +201,11 @@  __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 83b9b5a8d112..f12d5c5ecc31 100644
--- a/fs/f2fs/acl.c
+++ b/fs/f2fs/acl.c
@@ -207,12 +207,10 @@  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(fi, inode->i_mode);
-			if (error == 0)
-				acl = NULL;
 		}
 		break;
 
diff --git a/fs/gfs2/acl.c b/fs/gfs2/acl.c
index 7b3143064af1..88e66aa516c4 100644
--- a/fs/gfs2/acl.c
+++ b/fs/gfs2/acl.c
@@ -79,17 +79,11 @@  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 df0c9af68d05..71b3087b7e32 100644
--- a/fs/hfsplus/posix_acl.c
+++ b/fs/hfsplus/posix_acl.c
@@ -68,8 +68,8 @@  int hfsplus_set_posix_acl(struct inode *inode, struct posix_acl *acl,
 	case ACL_TYPE_ACCESS:
 		xattr_name = POSIX_ACL_XATTR_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 2f7a3c090489..f9f86f87d32b 100644
--- a/fs/jffs2/acl.c
+++ b/fs/jffs2/acl.c
@@ -235,9 +235,10 @@  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;
@@ -249,8 +250,6 @@  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 0c8ca830b113..9fad9f4fe883 100644
--- a/fs/jfs/acl.c
+++ b/fs/jfs/acl.c
@@ -84,13 +84,11 @@  static int __jfs_set_acl(tid_t tid, struct inode *inode, int type,
 	case ACL_TYPE_ACCESS:
 		ea_name = POSIX_ACL_XATTR_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 8a7d2f812b5b..c7641f656494 100644
--- a/fs/ocfs2/acl.c
+++ b/fs/ocfs2/acl.c
@@ -241,20 +241,16 @@  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;
-			else {
-				if (ret == 0)
-					acl = NULL;
+			umode_t mode;
 
-				ret = ocfs2_acl_set_mode(inode, di_bh,
-							 handle, mode);
-				if (ret)
-					return ret;
+			ret = posix_acl_update_mode(inode, &mode, &acl);
+			if (ret)
+				return ret;
 
-			}
+			ret = ocfs2_acl_set_mode(inode, di_bh,
+						 handle, mode);
+			if (ret)
+				return ret;
 		}
 		break;
 	case ACL_TYPE_DEFAULT:
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 3de7c223c963..38c91932eb52 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -594,6 +594,37 @@  no_acl:
 }
 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 4b34b9dc03dd..9b1824f35501 100644
--- a/fs/reiserfs/xattr_acl.c
+++ b/fs/reiserfs/xattr_acl.c
@@ -246,13 +246,9 @@  __reiserfs_set_acl(struct reiserfs_transaction_handle *th, struct inode *inode,
 	case ACL_TYPE_ACCESS:
 		name = POSIX_ACL_XATTR_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 a65fa5dde6e9..e0406717edbc 100644
--- a/fs/xfs/xfs_acl.c
+++ b/fs/xfs/xfs_acl.c
@@ -286,16 +286,11 @@  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 3e96a6a76103..d1a8ad7e5ae4 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -95,6 +95,7 @@  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 *);