[PATCH 3.2 148/152] posix_acl: Clear SGID bit when setting file permissions
From: Ben Hutchings
Date: Sun Nov 13 2016 - 21:13:37 EST
3.2.84-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Jan Kara <jack@xxxxxxx>
commit 073931017b49d9458aa351605b43a7e34598caef upstream.
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@xxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
[bwh: Backported to 3.2:
- Drop changes to ceph, f2fs, hfsplus, orangefs
- Use capable() instead of capable_wrt_inode_uidgid()
- Update ext3 and generic_acl.c as well
- In gfs2, jfs, and xfs, take care to avoid leaking the allocated ACL if
posix_acl_update_mode() determines it's not needed
- Adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/fs/9p/acl.c
+++ b/fs/9p/acl.c
@@ -319,32 +319,26 @@ static int v9fs_xattr_set_acl(struct den
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:
--- a/fs/btrfs/acl.c
+++ b/fs/btrfs/acl.c
@@ -118,11 +118,9 @@ static int btrfs_set_acl(struct btrfs_tr
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;
--- a/fs/ext2/acl.c
+++ b/fs/ext2/acl.c
@@ -194,15 +194,11 @@ ext2_set_acl(struct inode *inode, int ty
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;
--- a/fs/ext3/acl.c
+++ b/fs/ext3/acl.c
@@ -199,15 +199,11 @@ ext3_set_acl(handle_t *handle, struct in
case ACL_TYPE_ACCESS:
name_index = EXT3_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;
- ext3_mark_inode_dirty(handle, inode);
- if (error == 0)
- acl = NULL;
- }
+ inode->i_ctime = CURRENT_TIME_SEC;
+ ext3_mark_inode_dirty(handle, inode);
}
break;
--- a/fs/ext4/acl.c
+++ b/fs/ext4/acl.c
@@ -198,15 +198,11 @@ ext4_set_acl(handle_t *handle, struct in
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;
--- a/fs/generic_acl.c
+++ b/fs/generic_acl.c
@@ -86,16 +86,17 @@ generic_acl_set(struct dentry *dentry, c
if (error)
goto failed;
switch (type) {
- case ACL_TYPE_ACCESS:
- error = posix_acl_equiv_mode(acl, &inode->i_mode);
- if (error < 0)
+ case ACL_TYPE_ACCESS: {
+ struct posix_acl *saved_acl = acl;
+
+ error = posix_acl_update_mode(inode, &inode->i_mode, &acl);
+ if (acl == NULL)
+ posix_acl_release(saved_acl);
+ if (error)
goto failed;
inode->i_ctime = CURRENT_TIME;
- if (error == 0) {
- posix_acl_release(acl);
- acl = NULL;
- }
break;
+ }
case ACL_TYPE_DEFAULT:
if (!S_ISDIR(inode->i_mode)) {
error = -EINVAL;
--- a/fs/gfs2/acl.c
+++ b/fs/gfs2/acl.c
@@ -277,16 +277,14 @@ static int gfs2_xattr_system_set(struct
goto out_release;
if (type == ACL_TYPE_ACCESS) {
- umode_t mode = inode->i_mode;
- error = posix_acl_equiv_mode(acl, &mode);
+ struct posix_acl *saved_acl = acl;
+ umode_t mode;
- if (error <= 0) {
- posix_acl_release(acl);
- acl = NULL;
-
- if (error < 0)
- return error;
- }
+ error = posix_acl_update_mode(inode, &mode, &acl);
+ if (error || acl == NULL)
+ posix_acl_release(saved_acl);
+ if (error)
+ return error;
error = gfs2_set_mode(inode, mode);
if (error)
--- a/fs/jffs2/acl.c
+++ b/fs/jffs2/acl.c
@@ -227,9 +227,10 @@ static int jffs2_set_acl(struct inode *i
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;
@@ -241,8 +242,6 @@ static int jffs2_set_acl(struct inode *i
if (rc < 0)
return rc;
}
- if (rc == 0)
- acl = NULL;
}
break;
case ACL_TYPE_DEFAULT:
--- a/fs/jfs/xattr.c
+++ b/fs/jfs/xattr.c
@@ -693,9 +693,11 @@ static int can_set_system_xattr(struct i
return rc;
}
if (acl) {
- rc = posix_acl_equiv_mode(acl, &inode->i_mode);
+ struct posix_acl *dummy = acl;
+
+ rc = posix_acl_update_mode(inode, &inode->i_mode, &dummy);
posix_acl_release(acl);
- if (rc < 0) {
+ if (rc) {
printk(KERN_ERR
"posix_acl_equiv_mode returned %d\n",
rc);
--- a/fs/ocfs2/acl.c
+++ b/fs/ocfs2/acl.c
@@ -247,14 +247,11 @@ static int ocfs2_set_acl(handle_t *handl
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)
+ umode_t mode;
+ ret = posix_acl_update_mode(inode, &mode, &acl);
+ if (ret)
return ret;
else {
- if (ret == 0)
- acl = NULL;
-
ret = ocfs2_acl_set_mode(inode, di_bh,
handle, mode);
if (ret)
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -341,6 +341,36 @@ static int posix_acl_create_masq(struct
return not_equiv;
}
+/**
+ * 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(CAP_FSETID))
+ mode &= ~S_ISGID;
+ *mode_p = mode;
+ return 0;
+}
+EXPORT_SYMBOL(posix_acl_update_mode);
+
/*
* Modify the ACL for the chmod syscall.
*/
--- a/fs/reiserfs/xattr_acl.c
+++ b/fs/reiserfs/xattr_acl.c
@@ -272,13 +272,9 @@ reiserfs_set_acl(struct reiserfs_transac
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:
--- a/fs/xfs/xfs_acl.c
+++ b/fs/xfs/xfs_acl.c
@@ -384,17 +384,14 @@ xfs_xattr_acl_set(struct dentry *dentry,
goto out_release;
if (type == ACL_TYPE_ACCESS) {
- umode_t mode = inode->i_mode;
- error = posix_acl_equiv_mode(acl, &mode);
-
- if (error <= 0) {
- posix_acl_release(acl);
- acl = NULL;
-
- if (error < 0)
- return error;
- }
+ struct posix_acl *saved_acl = acl;
+ umode_t mode;
+ error = posix_acl_update_mode(inode, &mode, &acl);
+ if (error || acl == NULL)
+ posix_acl_release(saved_acl);
+ if (error)
+ return error;
error = xfs_set_mode(dentry, inode, mode);
if (error)
goto out_release;
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -83,6 +83,7 @@ extern struct posix_acl *posix_acl_from_
extern int posix_acl_equiv_mode(const struct posix_acl *, umode_t *);
extern int posix_acl_create(struct posix_acl **, gfp_t, umode_t *);
extern int posix_acl_chmod(struct posix_acl **, gfp_t, umode_t);
+extern int posix_acl_update_mode(struct inode *, umode_t *, struct posix_acl **);
extern struct posix_acl *get_posix_acl(struct inode *, int);
extern int set_posix_acl(struct inode *, int, struct posix_acl *);