[PATCH 6.18 397/752] xfrm6: fix uninitialized saddr in xfrm6_get_saddr()

Sasha Levin
2026-02-28T17:53:40Z

From: Jiayuan Chen <jiayuan.chen@shopee.com>

[ Upstream commit 1799d8abeabc68ec05679292aaf6cba93b343c05 ]

xfrm6_get_saddr() does not check the return value of
ipv6_dev_get_saddr(). When ipv6_dev_get_saddr() fails to find a suitable
source address (returns -EADDRNOTAVAIL), saddr->in6 is left
uninitialized, but xfrm6_get_saddr() still returns 0 (success).

This causes the caller xfrm_tmpl_resolve_one() to use the uninitialized
address in xfrm_state_find(), triggering KMSAN warning:

=====================================================
BUG: KMSAN: uninit-value in xfrm_state_find+0x2424/0xa940
xfrm_state_find+0x2424/0xa940
xfrm_resolve_and_create_bundle+0x906/0x5a20
xfrm_lookup_with_ifid+0xcc0/0x3770
xfrm_lookup_route+0x63/0x2b0
ip_route_output_flow+0x1ce/0x270
udp_sendmsg+0x2ce1/0x3400
inet_sendmsg+0x1ef/0x2a0
__sock_sendmsg+0x278/0x3d0
__sys_sendto+0x593/0x720
__x64_sys_sendto+0x130/0x200
x64_sys_call+0x332b/0x3e70
do_syscall_64+0xd3/0xf80
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable tmp.i.i created at:
xfrm_resolve_and_create_bundle+0x3e3/0x5a20
xfrm_lookup_with_ifid+0xcc0/0x3770
=====================================================

Fix by checking the return value of ipv6_dev_get_saddr() and propagating
the error.

Fixes: a1e59abf8249 ("[XFRM]: Fix wildcard as tunnel source")
Reported-by: syzbot+e136d86d34b42399a8b1@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68bf1024.a70a0220.7a912.02c2.GAE@google.com/T/
Signed-off-by: Jiayuan Chen <jiayuan.chen@shopee.com>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/xfrm6_policy.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/xfrm6_policy.c b/net/ipv6/xfrm6_policy.c
index 1f19b6f14484c..125ea9a5b8a08 100644
--- a/net/ipv6/xfrm6_policy.c
+++ b/net/ipv6/xfrm6_policy.c
@@ -57,6 +57,7 @@ static int xfrm6_get_saddr(xfrm_address_t *saddr,
struct dst_entry *dst;
struct net_device *dev;
struct inet6_dev *idev;
+ int err;

dst = xfrm6_dst_lookup(params);
if (IS_ERR(dst))
@@ -68,9 +69,11 @@ static int xfrm6_get_saddr(xfrm_address_t *saddr,
return -EHOSTUNREACH;
}
dev = idev->dev;
- ipv6_dev_get_saddr(dev_net(dev), dev, &params->daddr->in6, 0,
- &saddr->in6);
+ err = ipv6_dev_get_saddr(dev_net(dev), dev, &params->daddr->in6, 0,
+ &saddr->in6);
dst_release(dst);
+ if (err)
+ return -EHOSTUNREACH;
return 0;
}

--
2.51.0