[PATCH 6.1] net: fix crash when config small gso_max_size/gso_ipv4_max_size

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From: Wang Liang <wangliang74@xxxxxxxxxx>

[ Upstream commit 9ab5cf19fb0e4680f95e506d6c544259bf1111c4 ]

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@xxxxxxxxxx>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://patch.msgid.link/20241023035213.517386-1-wangliang74@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
[ Resolve minor conflicts to fix CVE-2024-50258 ]
Signed-off-by: Bin Lan <bin.lan.cn@xxxxxxxxxxxxx>
---
 net/core/rtnetlink.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index afb52254a47e..45c54fb9ad03 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1939,7 +1939,7 @@ 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 },
-- 
2.43.0





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