From: "sapatel at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: systemtap@sourceware.org
Subject: [Bug bpf/25298] New: stapbpf unused blocks may cause segmentation fault
Date: Thu, 19 Dec 2019 17:24:00 -0000 [thread overview]
Message-ID: <bug-25298-6586@http.sourceware.org/bugzilla/> (raw)
https://sourceware.org/bugzilla/show_bug.cgi?id=25298
Bug ID: 25298
Summary: stapbpf unused blocks may cause segmentation fault
Product: systemtap
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: bpf
Assignee: systemtap at sourceware dot org
Reporter: sapatel at redhat dot com
Target Milestone: ---
The bpf-optimizer removes any unreachable blocks. As per the current
implementation, these blocks are removed in the following manner.
--------------------------------------------------------------------------------
// Remove any unreachable blocks.
for (unsigned i = 0; i < nblocks; ++i)
if (!visited[i])
delete p.blocks[i];
--------------------------------------------------------------------------------
However, there could be the case where some unused blocks may lead to other
unused blocks. For example, Block 1 and Block 3 may be unused blocks, and Block
3 leads to Block 1. After Block 1 is deleted, the optimizer will attempt to
delete Block 3 as well. At this time, it may run into a segmentation fault as
Block 3 still contains some references to Block 1.
This problem has been discovered in the work of PR22315.
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next reply other threads:[~2019-12-19 17:24 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-19 17:24 sapatel at redhat dot com [this message]
2019-12-19 17:24 ` [Bug bpf/25298] " sapatel at redhat dot com
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