| Message ID | 20240216233128.work.366-kees@kernel.org (mailing list archive) |
|---|---|
| State | Awaiting Upstream |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | netfilter: x_tables: Use unsafe_memcpy() for 0-sized destination | expand |
On Fri, Feb 16, 2024 at 03:31:32PM -0800, Kees Cook wrote: > The struct xt_entry_target fake flexible array has not be converted to a > true flexible array, which is mainly blocked by it being both UAPI and > used in the middle of other structures. In order to properly check for > 0-sized destinations in memcpy(), an exception must be made for the one > place where it is still a destination. Since memcpy() was already > skipping checks for 0-sized destinations, using unsafe_memcpy() is no > change in behavior. > > Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Simon Horman <horms@kernel.org>
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c index 21624d68314f..da5d929c7c85 100644 --- a/net/netfilter/x_tables.c +++ b/net/netfilter/x_tables.c @@ -1142,7 +1142,8 @@ void xt_compat_target_from_user(struct xt_entry_target *t, void **dstptr, if (target->compat_from_user) target->compat_from_user(t->data, ct->data); else - memcpy(t->data, ct->data, tsize - sizeof(*ct)); + unsafe_memcpy(t->data, ct->data, tsize - sizeof(*ct), + /* UAPI 0-sized destination */); tsize += off; t->u.user.target_size = tsize;
The struct xt_entry_target fake flexible array has not be converted to a true flexible array, which is mainly blocked by it being both UAPI and used in the middle of other structures. In order to properly check for 0-sized destinations in memcpy(), an exception must be made for the one place where it is still a destination. Since memcpy() was already skipping checks for 0-sized destinations, using unsafe_memcpy() is no change in behavior. Signed-off-by: Kees Cook <keescook@chromium.org> --- Cc: Pablo Neira Ayuso <pablo@netfilter.org> Cc: Jozsef Kadlecsik <kadlec@netfilter.org> Cc: Florian Westphal <fw@strlen.de> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <edumazet@google.com> Cc: Jakub Kicinski <kuba@kernel.org> Cc: Paolo Abeni <pabeni@redhat.com> Cc: Gustavo A. R. Silva <gustavo@embeddedor.com> Cc: netfilter-devel@vger.kernel.org Cc: coreteam@netfilter.org Cc: netdev@vger.kernel.org --- net/netfilter/x_tables.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)