Messages in this thread | | | From | David Howells <> | Subject | Re: [PATCH] afs: Fix poential UAF in afs_make_call | Date | Wed, 11 Jan 2023 15:13:01 +0000 |
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Zheng Wang <zyytlz.wz@163.com> wrote:
> There is a function call : afs_fs_get_capabilities calls afs_make_call, in > afs_make_call, if error occurs in rxrpc_kernel_send_data, it will call > afs_put_call twice, which will free the call. And the access of > call->state will trigger a use-after-free bug.
Are you sure of that? Did you actually trigger a UAF?
> - if (cancel_work_sync(&call->async_work)) > - afs_put_call(call); > + cancel_work_sync(&call->async_work);
The problem with this change is that it will leak a ref if the work item was queued but gets cancelled before being run, given to it here:
static void afs_wake_up_async_call(struct sock *sk, struct rxrpc_call *rxcall, unsigned long call_user_ID) { struct afs_call *call = (struct afs_call *)call_user_ID; int r;
trace_afs_notify_call(rxcall, call); call->need_attention = true;
if (__refcount_inc_not_zero(&call->ref, &r)) { <---- trace_afs_call(call->debug_id, afs_call_trace_wake, r + 1, atomic_read(&call->net->nr_outstanding_calls), __builtin_return_address(0));
if (!queue_work(afs_async_calls, &call->async_work)) afs_put_call(call); } }
I *think* that cancel_work_sync() returns false if the work item is executing, but hasn't been requeued.
David
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