* [Bug bpf/25298] stapbpf unused blocks may cause segmentation fault
2019-12-19 17:24 [Bug bpf/25298] New: stapbpf unused blocks may cause segmentation fault sapatel at redhat dot com
@ 2019-12-19 17:24 ` sapatel at redhat dot com
0 siblings, 0 replies; 2+ messages in thread
From: sapatel at redhat dot com @ 2019-12-19 17:24 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=25298
Sagar Patel <sapatel at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|systemtap at sourceware dot org |sapatel at redhat dot com
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* [Bug bpf/25298] New: stapbpf unused blocks may cause segmentation fault
@ 2019-12-19 17:24 sapatel at redhat dot com
2019-12-19 17:24 ` [Bug bpf/25298] " sapatel at redhat dot com
0 siblings, 1 reply; 2+ messages in thread
From: sapatel at redhat dot com @ 2019-12-19 17:24 UTC (permalink / raw)
To: systemtap
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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2019-12-19 17:24 [Bug bpf/25298] New: stapbpf unused blocks may cause segmentation fault sapatel at redhat dot com
2019-12-19 17:24 ` [Bug bpf/25298] " sapatel at redhat dot com
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