Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions).
As found with Coccinelle[1], add __counted_by for struct tc_pedit. Additionally, since the element count member must be set before accessing the annotated flexible array member, move its initialization earlier. Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1] Signed-off-by: Kees Cook <[email protected]> --- Cc: Jakub Kicinski <[email protected]> Cc: Jamal Hadi Salim <[email protected]> Cc: Cong Wang <[email protected]> Cc: Jiri Pirko <[email protected]> Cc: "David S. Miller" <[email protected]> Cc: Eric Dumazet <[email protected]> Cc: Paolo Abeni <[email protected]> Cc: "Gustavo A. R. Silva" <[email protected]> Cc: [email protected] Cc: [email protected] --- include/uapi/linux/tc_act/tc_pedit.h | 2 +- net/sched/act_pedit.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/tc_act/tc_pedit.h b/include/uapi/linux/tc_act/tc_pedit.h index f3e61b04fa01..f5cab7fc96ab 100644 --- a/include/uapi/linux/tc_act/tc_pedit.h +++ b/include/uapi/linux/tc_act/tc_pedit.h @@ -62,7 +62,7 @@ struct tc_pedit_sel { tc_gen; unsigned char nkeys; unsigned char flags; - struct tc_pedit_key keys[0]; + struct tc_pedit_key keys[] __counted_by(nkeys); }; #define tc_pedit tc_pedit_sel diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c index 2ef22969f274..21e863d2898c 100644 --- a/net/sched/act_pedit.c +++ b/net/sched/act_pedit.c @@ -515,11 +515,11 @@ static int tcf_pedit_dump(struct sk_buff *skb, struct tc_action *a, spin_unlock_bh(&p->tcf_lock); return -ENOBUFS; } + opt->nkeys = parms->tcfp_nkeys; memcpy(opt->keys, parms->tcfp_keys, flex_array_size(opt, keys, parms->tcfp_nkeys)); opt->index = p->tcf_index; - opt->nkeys = parms->tcfp_nkeys; opt->flags = parms->tcfp_flags; opt->action = p->tcf_action; opt->refcnt = refcount_read(&p->tcf_refcnt) - ref; -- 2.34.1
