net: fix crash when config small gso_max_size/gso_ipv4_max_size

Config a small gso_max_size/gso_ipv4_max_size will lead to an underflow
in sk_dst_gso_max_size(), which may trigger a BUG_ON crash,
because sk->sk_gso_max_size would be much bigger than device limits.
Call Trace:
tcp_write_xmit
    tso_segs = tcp_init_tso_segs(skb, mss_now);
        tcp_set_skb_tso_segs
            tcp_skb_pcount_set
                // skb->len = 524288, mss_now = 8
                // u16 tso_segs = 524288/8 = 65535 -> 0
                tso_segs = DIV_ROUND_UP(skb->len, mss_now)
    BUG_ON(!tso_segs)
Add check for the minimum value of gso_max_size and gso_ipv4_max_size.

Fixes: 46e6b992c250 ("rtnetlink: allow GSO maximums to be set on device creation")
Fixes: 9eefedd58ae1 ("net: add gso_ipv4_max_size and gro_ipv4_max_size per device")
Signed-off-by: Wang Liang <wangliang74@huawei.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241023035213.517386-1-wangliang74@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index e30e7ea0207d0ce82600851c36df0b7fcae64ae4..2ba5cd965d3faed91f3ddcb075eef597032aaa71 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2032,7 +2032,7 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
        [IFLA_NUM_TX_QUEUES]    = { .type = NLA_U32 },
        [IFLA_NUM_RX_QUEUES]    = { .type = NLA_U32 },
        [IFLA_GSO_MAX_SEGS]     = { .type = NLA_U32 },
-       [IFLA_GSO_MAX_SIZE]     = { .type = NLA_U32 },
+       [IFLA_GSO_MAX_SIZE]     = NLA_POLICY_MIN(NLA_U32, MAX_TCP_HEADER + 1),
        [IFLA_PHYS_PORT_ID]     = { .type = NLA_BINARY, .len = MAX_PHYS_ITEM_ID_LEN },
        [IFLA_CARRIER_CHANGES]  = { .type = NLA_U32 },  /* ignored */
        [IFLA_PHYS_SWITCH_ID]   = { .type = NLA_BINARY, .len = MAX_PHYS_ITEM_ID_LEN },
@@ -2057,7 +2057,7 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
        [IFLA_TSO_MAX_SIZE]     = { .type = NLA_REJECT },
        [IFLA_TSO_MAX_SEGS]     = { .type = NLA_REJECT },
        [IFLA_ALLMULTI]         = { .type = NLA_REJECT },
-       [IFLA_GSO_IPV4_MAX_SIZE]        = { .type = NLA_U32 },
+       [IFLA_GSO_IPV4_MAX_SIZE]        = NLA_POLICY_MIN(NLA_U32, MAX_TCP_HEADER + 1),
        [IFLA_GRO_IPV4_MAX_SIZE]        = { .type = NLA_U32 },
 };