Bug 107307 - Exec Shield in 2.6 kernel causes random executable crashes
Exec Shield in 2.6 kernel causes random executable crashes
Status: CLOSED CURRENTRELEASE
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
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i686 Linux
medium Severity high
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Assigned To: Arjan van de Ven
Brian Brock
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Depends On:
Blocks:
  Show dependency treegraph
 
Reported: 2003-10-16 15:04 EDT by Daniel Walsh
Modified: 2007-11-30 17:10 EST (History)
1 user (show)

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Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2004-09-21 14:55:33 EDT
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Attachments (Terms of Use)
reproducer program for kernel stack bug (1021 bytes, text/plain)
2003-10-16 15:58 EDT, Roland McGrath
no flags Details
fix for overflow in expand_stack rlimit check (1.17 KB, patch)
2003-10-16 16:23 EDT, Roland McGrath
no flags Details | Diff

  None (edit)
Description Daniel Walsh 2003-10-16 15:04:18 EDT
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.5) Gecko/20030927

Description of problem:
System seems unstable with 2.6 kernel and exec shield installed.  I have seen
emacs, find, gcc and prelink fail with segfaults.

Version-Release number of selected component (if applicable):
 2.6.0-0.test7.1.57

How reproducible:
Always

Steps to Reproduce:
1.Install  2.6.0-0.test7.1.57 kernel
2. set /proc/sys/kernel/exec_shield to 1
3. run rpmbuild --rebuild prelink*src.rpm
4. Build crashes
5. set /proc/sys/kernel/exec_shield to 0
6. run rpmbuild --rebuild prelink*src.rpm
7. Build succeeds
    

Actual Results:  Seg faults

Expected Results:  No Seg Faults

Additional info:

I am doing this testing on an box with SELinux enabled.  Although I have turned
off the SELinux and still seen this behaviour.  The crashes do not happen in the
same place ever time.  I have started emacs had it crash and recall command and
it works.
Comment 1 Roland McGrath 2003-10-16 15:59:00 EDT
Created attachment 95234 [details]
reproducer program for kernel stack bug

This test program reproduces the bug every time run with an argument >= 2.
This happens for me even with /proc/sys/kernel/exec-shield set to 0,
on kernel-smp-2.6.0-0.test7.1.59.i686 (on dual PIII).
It does not happen with my own build of vanilla 2.6.
Comment 2 Roland McGrath 2003-10-16 16:23:16 EDT
Created attachment 95237 [details]
fix for overflow in expand_stack rlimit check

I think I got it by dead reckoning.  When the limit is set to RLIM_INFINITY,
the check in expand_stack will overflow and give a false positive.

I haven't tried this patch, but it probably fixes it.
Comment 3 Daniel Walsh 2004-09-21 14:55:33 EDT
Seems to be fixed.

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