Re: [syzbot] WARNING in u32_change
From: Kees Cook <hidden>
Date: 2022-09-26 02:52:32
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On Sun, Sep 25, 2022 at 07:39:23PM -0700, Kees Cook wrote:
quoted hunk ↗ jump to hunk
On Sun, Sep 25, 2022 at 10:34:37AM -0700, Eric Dumazet wrote:quoted
Sure, please look at: commit 54d9469bc515dc5fcbc20eecbe19cea868b70d68 Author: Kees Cook [off-list ref] Date: Thu Jun 24 15:39:26 2021 -0700 fortify: Add run-time WARN for cross-field memcpy() [...] Here, we might switch to unsafe_memcpy() instead of memcpy()I would tend to agree. Something like:diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c index 4d27300c287c..21e0e6206ecc 100644 --- a/net/sched/cls_u32.c +++ b/net/sched/cls_u32.c@@ -1040,7 +1040,9 @@ static int u32_change(struct net *net, struct sk_buff *in_skb, } #endif - memcpy(&n->sel, s, sel_size); + unsafe_memcpy(&n->sel, s, sel_size, + /* A composite flex-array structure destination, + * which was correctly sized and allocated above. */); RCU_INIT_POINTER(n->ht_up, ht); n->handle = handle; n->fshift = s->hmask ? ffs(ntohl(s->hmask)) - 1 : 0;
Ah, there is another in the same source file, in u32_init_knode():
memcpy(&new->sel, s, struct_size(s, keys, s->nkeys));
(I've been trying to convince Coccinelle to produce a list of all the
composite structure targets, but I keep running into weird glitches.
That it hadn't found this one let me track down the latest issue, so now
I should be able to find more! Whew.)
--
Kees Cook