On Tue, May 3, 2022 at 9:57 PM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > As part of the work to perform bounds checking on all memcpy() uses, > replace the open-coded a deserialization of bytes out of memory into a > trailing flexible array by using a flex_array.h helper to perform the > allocation, bounds checking, and copying: > > struct xfrm_sec_ctx > struct sidtab_str_cache > > Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx> > Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> > Cc: "David S. Miller" <davem@xxxxxxxxxxxxx> > Cc: Paul Moore <paul@xxxxxxxxxxxxxx> > Cc: Stephen Smalley <stephen.smalley.work@xxxxxxxxx> > Cc: Eric Paris <eparis@xxxxxxxxxxxxxx> > Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > Cc: Xiu Jianfeng <xiujianfeng@xxxxxxxxxx> > Cc: "Christian Göttsche" <cgzones@xxxxxxxxxxxxxx> > Cc: netdev@xxxxxxxxxxxxxxx > Cc: selinux@xxxxxxxxxxxxxxx > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > --- > include/uapi/linux/xfrm.h | 4 ++-- > security/selinux/ss/sidtab.c | 9 +++------ > security/selinux/xfrm.c | 7 ++----- > 3 files changed, 7 insertions(+), 13 deletions(-) > > diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h > index 65e13a099b1a..4a6fa2beff6a 100644 > --- a/include/uapi/linux/xfrm.h > +++ b/include/uapi/linux/xfrm.h > @@ -31,9 +31,9 @@ struct xfrm_id { > struct xfrm_sec_ctx { > __u8 ctx_doi; > __u8 ctx_alg; > - __u16 ctx_len; > + __DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(__u16, ctx_len); > __u32 ctx_sid; > - char ctx_str[0]; > + __DECLARE_FLEX_ARRAY_ELEMENTS(char, ctx_str); > }; While I like the idea of this in principle, I'd like to hear about the testing you've done on these patches. A previous flex array conversion in the audit uapi headers ended up causing a problem with GCC12 and SWIG; while it was a SWIG problem and not a kernel header problem that was thin consolation for those with broken builds. > diff --git a/security/selinux/ss/sidtab.c b/security/selinux/ss/sidtab.c > index a54b8652bfb5..a9d434e8cff7 100644 > --- a/security/selinux/ss/sidtab.c > +++ b/security/selinux/ss/sidtab.c > @@ -23,8 +23,8 @@ struct sidtab_str_cache { > struct rcu_head rcu_member; > struct list_head lru_member; > struct sidtab_entry *parent; > - u32 len; > - char str[]; > + DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(u32, len); > + DECLARE_FLEX_ARRAY_ELEMENTS(char, str); > }; > > #define index_to_sid(index) ((index) + SECINITSID_NUM + 1) -- paul-moore.com