Bug 85018 - SMP Register Corruption
SMP Register Corruption
Product: Red Hat Linux
Classification: Retired
Component: kernel (Show other bugs)
i686 Linux
high Severity high
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Assigned To: Arjan van de Ven
Brian Brock
Depends On:
  Show dependency treegraph
Reported: 2003-02-24 16:57 EST by Need Real Name
Modified: 2005-10-31 17:00 EST (History)
2 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2003-12-16 20:48:47 EST
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description Need Real Name 2003-02-24 16:57:23 EST
Description of problem:

Following text has been replicated verbatim from original patch submission from 
John Byrne. See URL above.

Currently, the SMP interrupt code generated by the macros
interrupt vector number on the stack. If the correct signal is pending
on the process and %eax happens to have the correct value, do_signal()
can be spoofed into adjusting %eax and %eip with almost certainly bad
results. For example, trying to do a "strace -p" the following program
will result in its dumping core with an illegal instruction.

int i;

asm (
"mov %1,%0\n\t"
"cmp %1,%0\n\t"
"je 1b\n\t"
:"=&a" (i)
:"i" (-512));

return i;

I suspect what was wanted was to subtract 256, as is done in BUILD_IRQ,
to make the values negative, but leave the vector available in %al, so
I offer the following patch against 2.4.10-pre2 to do so. (The 2.2.x
code simply pushes -1. I don't see anything that uses the vector for
these interrupt, so this should work. However, I assume the change was
made so the vector number would be available on the stack, perhaps for

This has only been tested by me on my SMP box, but... (I don't want to
complete that sentence with words I might be forced to regret for some

Version-Release number of selected component (if applicable):
LAS 2.1
Red Hat 7.1

How reproducible:

Steps to Reproduce:
1. See URL above for sample program
Actual results:

Expected results:

Additional info:
Comment 1 Arjan van de Ven 2003-02-24 17:34:22 EST
the most current 7.1 kernel is 2.4.18-24.... I'd expect it to be fixed there....
Comment 2 Paul Hansen 2003-02-25 09:21:29 EST
This bug was found in RedHat 7.1.  The patch has been incorporated
in Linux Advanced Server 2.1, as I verified from the source code.
As our upgrade plans are to go from 7.1 to LAS 2.1, I don't think
any further action is necessary on this bug; the fix is to upgrade. 

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