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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I would like to report a bug I found lately in LTP testcase source code.<o:p></o:p></p>
<p class="MsoNormal">The bug is located at: <a href="https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/fs/read_all/read_all.c#L123">
https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/fs/read_all/read_all.c#L123</a>
<o:p></o:p></p>
<p class="MsoNormal">This bug may cause the read_all testcase terminated unexpectedly before the reading thread complete its job.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In the source code, at the end of the function <b>queue_pop()</b>, it stores i + 1 into the q->front to update the front indicator.
<o:p></o:p></p>
<p class="MsoNormal">But under some circumstances it will store 16384 which is the default length of the queue size.<o:p></o:p></p>
<p class="MsoNormal">When this happens, the next time <b>queue_pop()</b> is called, it will perform a read action that overstep the array boundary which is q->data[16384].<o:p></o:p></p>
<p class="MsoNormal">If the value stored there is 0, the <b>queue_pop()</b> will immediately return 0 and the whole testcase is broken.<o:p></o:p></p>
<p class="MsoNormal">This happens when there is a whole file path stores exactly at the end of the
<b>data</b> array. In this situation, i equals 16383 when while() ends.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Modifying i + 1 to (i + 1) % QUEUE_SIZE at the source code Line#123 can easily fix it.<o:p></o:p></p>
<p class="MsoNormal">This bug is not triggered on every machine because the files are different between target machine.
<o:p></o:p></p>
<p class="MsoNormal">Adjust the length of the QUEUE_SIZE will help you reproduce this bug.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Regards,<o:p></o:p></p>
<p class="MsoNormal">Xiang<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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