[PATCH bpf-next] bpf: Silence Coverity warning for find_kfunc_desc_btf

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

The helper function returns a pointer that in the failure case encodes
an error in the struct btf pointer. The current code lead to Coverity
warning about the use of the invalid pointer:

 *** CID 1507963:  Memory - illegal accesses  (USE_AFTER_FREE)
 /kernel/bpf/verifier.c: 1788 in find_kfunc_desc_btf()
 1782                          return ERR_PTR(-EINVAL);
 1783                  }
 1784
 1785                  kfunc_btf = __find_kfunc_desc_btf(env, offset, btf_modp);
 1786                  if (IS_ERR_OR_NULL(kfunc_btf)) {
 1787                          verbose(env, "cannot find module BTF for func_id %u\n", func_id);
 >>>      CID 1507963:  Memory - illegal accesses  (USE_AFTER_FREE)
 >>>      Using freed pointer "kfunc_btf".
 1788                          return kfunc_btf ?: ERR_PTR(-ENOENT);
 1789                  }
 1790                  return kfunc_btf;
 1791          }
 1792          return btf_vmlinux ?: ERR_PTR(-ENOENT);
 1793     }

Daniel suggested the use of ERR_CAST so that the intended use is clear
to Coverity, but on closer look it seems that we never return NULL from
the helper, hence it can just be switched to checking for IS_ERR and
returning the pointer, similar to the cases elsewhere in the kernel.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/verifier.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 20900a1bac12..2551b6be8d42 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1783,10 +1783,8 @@ static struct btf *find_kfunc_desc_btf(struct bpf_verifier_env *env,
 		}

 		kfunc_btf = __find_kfunc_desc_btf(env, offset, btf_modp);
-		if (IS_ERR_OR_NULL(kfunc_btf)) {
+		if (IS_ERR(kfunc_btf))
 			verbose(env, "cannot find module BTF for func_id %u\n", func_id);
-			return kfunc_btf ?: ERR_PTR(-ENOENT);
-		}
 		return kfunc_btf;
 	}
 	return btf_vmlinux ?: ERR_PTR(-ENOENT);
--
2.33.0