From: Kyle Zeng <kylebot@openai.com> mainline inclusion from mainline-v7.2-rc7 commit 0e243671bc7b8eaf00f83dd2f4367436dc0cff98 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/18316 CVE: CVE-2026-74630 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- in6_dev_get() reads dev->ip6_ptr under RCU and then unconditionally increments its refcount. Device teardown can clear the pointer and drop the last reference between these operations. The increment then resurrects an object whose RCU free has already been queued, so callers can use it after it is freed. Use refcount_inc_not_zero() and return NULL when the object has already reached zero. RCU keeps the memory accessible through the attempted reference acquisition, and a successful increment pins the object for the caller. An independent run on the exact unpatched 6f5156d7a31a (v7.2-rc3) kernel reproduced the invalid reference acquisition as UID 1000: refcount_t: addition on 0; use-after-free. ip6_mc_source+0xef4/0x17e0 It was followed by the corresponding reference underflow in ip6_mc_source(). The supplied trace from the same unpatched revision additionally shows the access after the RCU read-side section ends: BUG: KASAN: slab-use-after-free in mutex_lock+0x76/0xe0 Write of size 8 at addr ffff888015b50240 by task poc/1219 Bug found and triaged by OpenAI Security Research and validated by Trail of Bits. Fixes: 8814c4b53381 ("[IPV6] ADDRCONF: Convert addrconf_lock to RCU.") Cc: stable@vger.kernel.org Signed-off-by: Kyle Zeng <kylebot@openai.com> Co-developed-by: David Lee <david.lee@trailofbits.com> Signed-off-by: David Lee <david.lee@trailofbits.com> Reviewed-by: Ido Schimmel <idosch@nvidia.com> Link: https://patch.msgid.link/20260803122758.666112-1-david.lee@trailofbits.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: JiangJieHua <jiangjiehua1@huawei.com> --- include/net/addrconf.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/net/addrconf.h b/include/net/addrconf.h index 10d270f004f0d..de1e3dd0c26b5 100644 --- a/include/net/addrconf.h +++ b/include/net/addrconf.h @@ -384,8 +384,8 @@ static inline struct inet6_dev *in6_dev_get(const struct net_device *dev) rcu_read_lock(); idev = rcu_dereference(dev->ip6_ptr); - if (idev) - refcount_inc(&idev->refcnt); + if (idev && !refcount_inc_not_zero(&idev->refcnt)) + idev = NULL; rcu_read_unlock(); return idev; } -- 2.33.8