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Commit 9f32911c authored by Mark Salyzyn's avatar Mark Salyzyn
Browse files

ANDROID: overlayfs: internal getxattr operations without sepolicy checking 



Check impure, opaque, origin & meta xattr with no sepolicy audit
(using __vfs_getxattr) since these operations are internal to
overlayfs operations and do not disclose any data.  This became
an issue for credential override off since sys_admin would have
been required by the caller; whereas would have been inherently
present for the creator since it performed the mount.

This is a change in operations since we do not check in the new
ovl_vfs_getxattr function if the credential override is off or
not.  Reasoning is that the sepolicy check is unnecessary overhead,
especially since the check can be expensive.

Signed-off-by: default avatarMark Salyzyn <salyzyn@google.com>
Bug: 133515582
Bug: 136124883
Bug: 129319403
Change-Id: I34d99cc46e9e87a79efc8d05f85980bbc137f7eb
parent 18cb05fa

fs/overlayfs/namei.c

+7 −5
Original line number Diff line number Diff line
@@ -109,10 +109,11 @@ int ovl_check_fh_len(struct ovl_fh *fh, int fh_len) 


static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name)

{

	int res, err;

	ssize_t res;

	int err;

	struct ovl_fh *fh = NULL;



	res = vfs_getxattr(dentry, name, NULL, 0);

	res = ovl_vfs_getxattr(dentry, name, NULL, 0);

	if (res < 0) {

		if (res == -ENODATA || res == -EOPNOTSUPP)

			return NULL;
@@ -126,7 +127,7 @@ static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name) 
	if (!fh)

		return ERR_PTR(-ENOMEM);



	res = vfs_getxattr(dentry, name, fh, res);

	res = ovl_vfs_getxattr(dentry, name, fh, res);

	if (res < 0)

		goto fail;
@@ -144,10 +145,11 @@ static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name) 
	return NULL;



fail:

	pr_warn_ratelimited("overlayfs: failed to get origin (%i)\n", res);

	pr_warn_ratelimited("overlayfs: failed to get origin (%zi)\n", res);

	goto out;

invalid:

	pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n", res, fh);

	pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n",

			    (int)res, fh);

	goto out;

}

fs/overlayfs/overlayfs.h

+2 −0
Original line number Diff line number Diff line
@@ -209,6 +209,8 @@ void ovl_drop_write(struct dentry *dentry); 
struct dentry *ovl_workdir(struct dentry *dentry);

const struct cred *ovl_override_creds(struct super_block *sb);

void ovl_revert_creds(const struct cred *oldcred);

ssize_t ovl_vfs_getxattr(struct dentry *dentry, const char *name, void *buf,

			 size_t size);

struct super_block *ovl_same_sb(struct super_block *sb);

int ovl_can_decode_fh(struct super_block *sb);

struct dentry *ovl_indexdir(struct super_block *sb);

fs/overlayfs/util.c

+15 −9
Original line number Diff line number Diff line
@@ -51,6 +51,12 @@ void ovl_revert_creds(const struct cred *old_cred) 
		revert_creds(old_cred);

}



ssize_t ovl_vfs_getxattr(struct dentry *dentry, const char *name, void *buf,

			 size_t size)

{

	return __vfs_getxattr(dentry, d_inode(dentry), name, buf, size);

}



struct super_block *ovl_same_sb(struct super_block *sb)

{

	struct ovl_fs *ofs = sb->s_fs_info;
@@ -549,9 +555,9 @@ void ovl_copy_up_end(struct dentry *dentry) 


bool ovl_check_origin_xattr(struct dentry *dentry)

{

	int res;

	ssize_t res;



	res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);

	res = ovl_vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);



	/* Zero size value means "copied up but origin unknown" */

	if (res >= 0)
@@ -562,13 +568,13 @@ bool ovl_check_origin_xattr(struct dentry *dentry) 


bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)

{

	int res;

	ssize_t res;

	char val;



	if (!d_is_dir(dentry))

		return false;



	res = vfs_getxattr(dentry, name, &val, 1);

	res = ovl_vfs_getxattr(dentry, name, &val, 1);

	if (res == 1 && val == 'y')

		return true;
@@ -852,13 +858,13 @@ int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir) 
/* err < 0, 0 if no metacopy xattr, 1 if metacopy xattr found */

int ovl_check_metacopy_xattr(struct dentry *dentry)

{

	int res;

	ssize_t res;



	/* Only regular files can have metacopy xattr */

	if (!S_ISREG(d_inode(dentry)->i_mode))

		return 0;



	res = vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0);

	res = ovl_vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0);

	if (res < 0) {

		if (res == -ENODATA || res == -EOPNOTSUPP)

			return 0;
@@ -867,7 +873,7 @@ int ovl_check_metacopy_xattr(struct dentry *dentry) 


	return 1;

out:

	pr_warn_ratelimited("overlayfs: failed to get metacopy (%i)\n", res);

	pr_warn_ratelimited("overlayfs: failed to get metacopy (%zi)\n", res);

	return res;

}
@@ -893,7 +899,7 @@ ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value, 
	ssize_t res;

	char *buf = NULL;



	res = vfs_getxattr(dentry, name, NULL, 0);

	res = ovl_vfs_getxattr(dentry, name, NULL, 0);

	if (res < 0) {

		if (res == -ENODATA || res == -EOPNOTSUPP)

			return -ENODATA;
@@ -905,7 +911,7 @@ ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value, 
		if (!buf)

			return -ENOMEM;



		res = vfs_getxattr(dentry, name, buf, res);

		res = ovl_vfs_getxattr(dentry, name, buf, res);

		if (res < 0)

			goto fail;

	}