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ANDROID: overlayfs: internal getxattr operations without sepolicy checking

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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: Mark Salyzyn <salyzyn@google.com>
Bug: 133515582
Bug: 136124883
Bug: 129319403
Change-Id: I34d99cc46e9e87a79efc8d05f85980bbc137f7eb
This commit is contained in:
Mark Salyzyn 2019-07-23 13:53:48 -07:00
parent 69e51290af
commit e2d54786e8
3 changed files with 24 additions and 14 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

12
fs/overlayfs/namei.c
View file

@ -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;
}

2
fs/overlayfs/overlayfs.h
View file

@ -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);

24
fs/overlayfs/util.c
View file

@ -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;
}