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net: sched: cls_u32: Avoid memcpy() false-positive warning in u32_init_knode()

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: syzbot+d5ace703ed883df56e42@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/69a811b9.a70a0220.b118c.0019.GAE@google.com/T/
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
Link: https://patch.msgid.link/20260309123917.402183-1-jiayuan.chen@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

authored by

Jiayuan Chen and committed by
Jakub Kicinski 34bd3c6b 9278b888

+4 -1
+4 -1
net/sched/cls_u32.c
··· 852 852 /* Similarly success statistics must be moved as pointers */ 853 853 new->pcpu_success = n->pcpu_success; 854 854 #endif 855 - memcpy(&new->sel, s, struct_size(s, keys, s->nkeys)); 855 + unsafe_memcpy(&new->sel, s, struct_size(s, keys, s->nkeys), 856 + /* A composite flex-array structure destination, 857 + * which was correctly sized with kzalloc_flex(), 858 + * above. */); 856 859 857 860 if (tcf_exts_init(&new->exts, net, TCA_U32_ACT, TCA_U32_POLICE)) { 858 861 kfree(new);