[PATCH v2 bpf] bpf: Fix memory leak in __lookup_instance error path

[Shardul Bankar <shardulsb08@gmail.com>]

When __lookup_instance() allocates a func_instance structure but fails
to allocate the must_write_set array, it returns an error without freeing
the previously allocated func_instance. This causes a memory leak of 192
bytes (sizeof(struct func_instance)) each time this error path is triggered.

Fix by freeing 'result' on must_write_set allocation failure.

Fixes: b3698c356ad9 ("bpf: callchain sensitive stack liveness tracking using CFG")
Reported-by: BPF Runtime Fuzzer (BRF)
Signed-off-by: Shardul Bankar <shardulsb08@gmail.com>
v2: Resend with complete CC list.
---
 kernel/bpf/liveness.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/liveness.c b/kernel/bpf/liveness.c
index 3c611aba7f52..1e6538f59a78 100644
--- a/kernel/bpf/liveness.c
+++ b/kernel/bpf/liveness.c
@@ -195,8 +195,10 @@ static struct func_instance *__lookup_instance(struct bpf_verifier_env *env,
 		return ERR_PTR(-ENOMEM);
 	result->must_write_set = kvcalloc(subprog_sz, sizeof(*result->must_write_set),
 					  GFP_KERNEL_ACCOUNT);
-	if (!result->must_write_set)
+	if (!result->must_write_set) {
+		kvfree(result);
 		return ERR_PTR(-ENOMEM);
+	}
 	memcpy(&result->callchain, callchain, sizeof(*callchain));
 	result->insn_cnt = subprog_sz;
 	hash_add(liveness->func_instances, &result->hl_node, key);
-- 
2.34.1