Messages in this thread | | | Subject | Re: CVE-2016-7097 causes acl leak | From | Mark Salyzyn <> | Date | Tue, 13 Dec 2016 07:55:23 -0800 |
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On 12/12/2016 10:26 PM, Cong Wang wrote: > On Mon, Dec 12, 2016 at 4:26 PM, Mark Salyzyn <salyzyn@android.com> wrote: >> The leaks were introduced in 9p, gfs2, jfs and xfs drivers only. > > Only the 9p case is obvious to me: > > diff --git a/fs/9p/acl.c b/fs/9p/acl.c > index b3c2cc7..082d227 100644 > --- a/fs/9p/acl.c > +++ b/fs/9p/acl.c > @@ -277,6 +277,7 @@ static int v9fs_xattr_set_acl(const struct > xattr_handler *handler, > case ACL_TYPE_ACCESS: > if (acl) { > struct iattr iattr; > + struct posix_acl *old_acl = acl; > > retval = posix_acl_update_mode(inode, > &iattr.ia_mode, &acl); > if (retval) > @@ -287,6 +288,7 @@ static int v9fs_xattr_set_acl(const struct > xattr_handler *handler, > * by the mode bits. So don't > * update ACL. > */ > + posix_acl_release(old_acl); > value = NULL; > size = 0; > } > > > The rest are anti-pattern (modifying parameters on stack via address) > but look correct I chose to modify posix_acl_update_mode as follows and set release_acl in the specific drivers, it clears the *acl reference to nul preventing posix_acl_release from functioning in these other driver paths:
*/ int posix_acl_update_mode(struct inode *inode, umode_t *mode_p, struct posix_acl **acl, ++++bool release_acl) { umode_t mode = inode->i_mode; int error;
error = posix_acl_equiv_mode(*acl, &mode); if (error < 0) return error; if (error == 0) +{ + if (release_acl) + posix_acl_release(*acl); *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);
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