On Wed, 2022-06-01 at 16:48 +0800, Wang Yufen wrote:
> Resurrect ubsan overflow checks and ubsan report this warning,
> fix it by change the variable [length] type to size_t.
>
> UBSAN: signed-integer-overflow in net/ipv6/ip6_output.c:1489:19
> 2147479552 + 8567 cannot be represented in type 'int'
> CPU: 0 PID: 253 Comm: err Not tainted 5.16.0+ #1
> Hardware name: linux,dummy-virt (DT)
> Call trace:
> dump_backtrace+0x214/0x230
> show_stack+0x30/0x78
> dump_stack_lvl+0xf8/0x118
> dump_stack+0x18/0x30
> ubsan_epilogue+0x18/0x60
> handle_overflow+0xd0/0xf0
> __ubsan_handle_add_overflow+0x34/0x44
> __ip6_append_data.isra.48+0x1598/0x1688
> ip6_append_data+0x128/0x260
> udpv6_sendmsg+0x680/0xdd0
> inet6_sendmsg+0x54/0x90
> sock_sendmsg+0x70/0x88
> ____sys_sendmsg+0xe8/0x368
> ___sys_sendmsg+0x98/0xe0
> __sys_sendmmsg+0xf4/0x3b8
> __arm64_sys_sendmmsg+0x34/0x48
> invoke_syscall+0x64/0x160
> el0_svc_common.constprop.4+0x124/0x300
> do_el0_svc+0x44/0xc8
> el0_svc+0x3c/0x1e8
> el0t_64_sync_handler+0x88/0xb0
> el0t_64_sync+0x16c/0x170
>
> Changes since v1:
> -Change the variable [length] type to unsigned, as Eric Dumazet suggested.
> Changes since v2:
> -Don't change exthdrlen type in ip6_make_skb, as Paolo Abeni suggested.
> Changes since v3:
> -Don't change ulen type in udpv6_sendmsg and l2tp_ip6_sendmsg, as
> Jakub Kicinski suggested.
I'm sorry for the multiple incremental feedback on this patch. It's
somewhat tricky.
AFAICS Jakub mentioned only udpv6_sendmsg(). In l2tp_ip6_sendmsg() we
can have an overflow:
int transhdrlen = 4; /* zero session-id */
int ulen = len + transhdrlen;
when len >= INT_MAX - 4. That will be harmless, but I guess it could
still trigger a noisy UBSAN splat.
Paolo
