[PATCH net v2] net: fix crash when config small gso_max_size/gso_ipv4_max_size

[PATCH net v2] net: fix crash when config small gso_max_size/gso_ipv4_max_size

[Wang Liang]

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>
---
 net/core/rtnetlink.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index e30e7ea0207d..2ba5cd965d3f 100644
--- 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 },
 };
 
-- 
2.34.1

Re: [PATCH net v2] net: fix crash when config small gso_max_size/gso_ipv4_max_size

[Eric Dumazet]

On Wed, Oct 23, 2024 at 5:34 AM Wang Liang <wangliang74@huawei.com> wrote:
>
> 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>
> ---

Thanks for this fix !

Reviewed-by: Eric Dumazet <edumazet@google.com>

回复: [PATCH net v2] net: fix crash when config small gso_max_size/gso_ipv4_max_size

[wangliang (CI)]

Thank you very much for your suggestions!

-----邮件原件-----
发件人: Eric Dumazet <edumazet@google.com> 
发送时间: 2024年10月23日 14:44
收件人: wangliang (CI) <wangliang74@huawei.com>
抄送: davem@davemloft.net; kuba@kernel.org; pabeni@redhat.com; idosch@nvidia.com; kuniyu@amazon.com; stephen@networkplumber.org; dsahern@kernel.org; lucien.xin@gmail.com; yuehaibing <yuehaibing@huawei.com>; zhangchangzhong <zhangchangzhong@huawei.com>; netdev@vger.kernel.org; linux-kernel@vger.kernel.org
主题: Re: [PATCH net v2] net: fix crash when config small gso_max_size/gso_ipv4_max_size

On Wed, Oct 23, 2024 at 5:34 AM Wang Liang <wangliang74@huawei.com> wrote:
>
> 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>
> ---

Thanks for this fix !

Reviewed-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH net v2] net: fix crash when config small gso_max_size/gso_ipv4_max_size

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 23 Oct 2024 11:52:13 +0800 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [net,v2] net: fix crash when config small gso_max_size/gso_ipv4_max_size
    https://git.kernel.org/netdev/net/c/9ab5cf19fb0e

You are awesome, thank you!
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