On 3/5/26 16:33, Jiayuan Chen wrote:
From: Jiayuan Chen <[email protected]> Syzbot reported a warning in u32_init_knode() [1]. Similar to commit 7cba18332e36 ("net: sched: cls_u32: Avoid memcpy() false-positive warning") which addressed the same issue in u32_change(), use unsafe_memcpy() in u32_init_knode() to work around the compiler's inability to see into composite flexible array structs. This silences the false-positive reported by syzbot: memcpy: detected field-spanning write (size 32) of single field "&new->sel" at net/sched/cls_u32.c:855 (size 16) Since the memory is correctly allocated with kzalloc_flex() using s->nkeys, this is purely a false positive and does not need a Fixes tag. [1] https://syzkaller.appspot.com/bug?extid=d5ace703ed883df56e42 Reported-by: [email protected] Closes: https://lore.kernel.org/all/[email protected]/T/ Signed-off-by: Jiayuan Chen <[email protected]>
Acked-by: Gustavo A. R. Silva <[email protected]> Thanks -Gustavo
Made-with: Cursor --- net/sched/cls_u32.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c index 9241c025aa74..8f30cc82181d 100644 --- a/net/sched/cls_u32.c +++ b/net/sched/cls_u32.c @@ -852,7 +852,10 @@ static struct tc_u_knode *u32_init_knode(struct net *net, struct tcf_proto *tp, /* Similarly success statistics must be moved as pointers */ new->pcpu_success = n->pcpu_success; #endif - memcpy(&new->sel, s, struct_size(s, keys, s->nkeys)); + unsafe_memcpy(&new->sel, s, struct_size(s, keys, s->nkeys), + /* A composite flex-array structure destination, + * which was correctly sized with kzalloc_flex(), + * above. */);if (tcf_exts_init(&new->exts, net, TCA_U32_ACT, TCA_U32_POLICE)) {kfree(new);
