ipvs: fix uninit-value for saddr in do_output_route4 (CVE-2025-37961)

Summary

ipvs: fix uninit-value for saddr in do_output_route4

Original description

The description as published by the source.

In the Linux kernel, the following vulnerability has been resolved:

ipvs: fix uninit-value for saddr in do_output_route4

syzbot reports for uninit-value for the saddr argument [1].
commit 4754957f04f5 ("ipvs: do not use random local source address for
tunnels") already implies that the input value of saddr
should be ignored but the code is still reading it which can prevent
to connect the route. Fix it by changing the argument to ret_saddr.

[1]
BUG: KMSAN: uninit-value in do_output_route4+0x42c/0x4d0 net/netfilter/ipvs/ip_vs_xmit.c:147
do_output_route4+0x42c/0x4d0 net/netfilter/ipvs/ip_vs_xmit.c:147
__ip_vs_get_out_rt+0x403/0x21d0 net/netfilter/ipvs/ip_vs_xmit.c:330
ip_vs_tunnel_xmit+0x205/0x2380 net/netfilter/ipvs/ip_vs_xmit.c:1136
ip_vs_in_hook+0x1aa5/0x35b0 net/netfilter/ipvs/ip_vs_core.c:2063
nf_hook_entry_hookfn include/linux/netfilter.h:154 [inline]
nf_hook_slow+0xf7/0x400 net/netfilter/core.c:626
nf_hook include/linux/netfilter.h:269 [inline]
__ip_local_out+0x758/0x7e0 net/ipv4/ip_output.c:118
ip_local_out net/ipv4/ip_output.c:127 [inline]
ip_send_skb+0x6a/0x3c0 net/ipv4/ip_output.c:1501
udp_send_skb+0xfda/0x1b70 net/ipv4/udp.c:1195
udp_sendmsg+0x2fe3/0x33c0 net/ipv4/udp.c:1483
inet_sendmsg+0x1fc/0x280 net/ipv4/af_inet.c:851
sock_sendmsg_nosec net/socket.c:712 [inline]
__sock_sendmsg+0x267/0x380 net/socket.c:727
____sys_sendmsg+0x91b/0xda0 net/socket.c:2566
___sys_sendmsg+0x28d/0x3c0 net/socket.c:2620
__sys_sendmmsg+0x41d/0x880 net/socket.c:2702
_…

Source: OSV.dev (Open Source Vulnerabilities) NVD OSV

Affected packages

Linux Kernel

[{"type":"ECOSYSTEM","events":[{"introduced":"4.2.0"},{"fixed":"6.1.139"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.91"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.29"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.14.7"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

BellSoft Alpaquita BELL-CVE-2025-37961 linux-lts Fixed in: 6.1.140-r0
Debian DEBIAN-CVE-2025-37961 linux
Ubuntu UBUNTU-CVE-2025-37961 linux

Summary

Original description

Affected packages

Fix status by distribution

References