Re: [PATCH v2 10/11] perf/uprobe: Convert single-step and uretprobe to SRCU
From: Oleg Nesterov <oleg@redhat.com>
Date: 2024-07-11 16:08:41
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lkml
I'll try to actually apply the whole series and read the code tomorrow. Right now I can't understand this change... Just one question for now. On 07/11, Peter Zijlstra wrote:
quoted hunk ↗ jump to hunk
@@ -1956,11 +1960,13 @@ static void prepare_uretprobe(struct upr * attack from user-space. */ uprobe_warn(current, "handle tail call"); - goto err_uprobe; + goto err_mem; } orig_ret_vaddr = utask->return_instances->orig_ret_vaddr; } + ri->srcu_idx = __srcu_read_lock(&uretprobes_srcu); + ri->uprobe = uprobe;
It seems that, if we race with _unregister, this __srcu_read_lock() can happen after call_srcu(uprobes_srcu, uprobe, uprobe_free_stage1) was already called... In this case read_lock "has no effect" in that uprobe_free_stage1() can run before free_ret_instance() does srcu_read_unlock(ri->srcu_idx). Perhaps it is fine, uprobe_free_stage1() does another call_srcu(), but somehow I got lost. Could you re-check this logic? Most probably I missed something, but still... Oleg.