xfrm: fix refcount leak in __xfrm_policy_check()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: xfrm: fix refcount leak in __xfrm_policy_check() The issue happens on an error path in __xfrm_policy_check(). When the fetching process of the object `pols[1]` fails, the function simply returns 0, forgetting to decrement the reference count of `pols[0]`, which is incremented earlier by either xfrm_sk_policy_lookup() or xfrm_policy_lookup(). This may result in memory leaks. Fix it by decreasing the reference count of `pols[0]` in that path.

References

• https://git.kernel.org/stable/c/18e6b6e2555c93f5ca09f2b85ef1fa025c8accea
• https://git.kernel.org/stable/c/8f94b933103ee1bda119543369cc18a1be5536db
• https://git.kernel.org/stable/c/0769491a8acd3e85ca4c3f65080eac2c824262df
• https://git.kernel.org/stable/c/63da7a2bbf3f28094920e0b8a17d2571a9bd842d
• https://git.kernel.org/stable/c/1305d7d4f35ca6f214a2d23b075aa6a924cff3be
• https://git.kernel.org/stable/c/26ad2398fe4984f4f6f930bcb3bc9047fa77265b
• https://git.kernel.org/stable/c/d66c052879791313f90c0584420f196a038fb8b8
• https://git.kernel.org/stable/c/9c9cb23e00ddf45679b21b4dacc11d1ae7961ebe