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Bug 191094 - fs/proc/task_mmu.c show_map() can OOPS
fs/proc/task_mmu.c show_map() can OOPS
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
All Linux
medium Severity medium
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Assigned To: Dave Jones
Brian Brock
Depends On:
  Show dependency treegraph
Reported: 2006-05-08 16:02 EDT by Jeff Johnson
Modified: 2015-01-04 17:27 EST (History)
2 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2006-11-12 17:07:23 EST
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
linux-2.6.9-show_map.patch (830 bytes, patch)
2006-05-08 21:25 EDT, Jeff Johnson
no flags Details | Diff
linux-2.6.16-show_map.patch (untested) (987 bytes, patch)
2006-05-09 09:52 EDT, Jeff Johnson
no flags Details | Diff

  None (edit)
Description Jeff Johnson 2006-05-08 16:02:53 EDT
(OOPS was seen on 2.6.9 kernel, same problem appears to exist on FC 2.6.16)

Intensive monitoint through /proc can/will OOPS under load.

The stack trace indicates that task->mm goes NULL in fs/proc/task_mmu.c show_map().

The attached patch (generated from CentOS 4.3 2.6.9 kernel sources, but
the same problem appears to be in FC devel kernels from inspection) takes
a refcount on task->mm using get_task_mm() and mmput().

Entirely untested patch, but the OOPS is real.
Comment 1 Jeff Johnson 2006-05-08 21:25:49 EDT
Created attachment 128768 [details]
Comment 2 Jeff Johnson 2006-05-09 09:52:40 EDT
Created attachment 128784 [details]
linux-2.6.16-show_map.patch (untested)
Comment 3 Jeff Johnson 2006-05-12 07:05:11 EDT
The original OOPS took about an hour to reproduce, intensively reading /proc.

With the linux-2.6.9-show_mappatch, two runs on CentOS kernel have completed more than 8 hours 
without problem.
Comment 4 Jeff Johnson 2006-05-12 09:48:56 EDT
24 hour run with the patch => no problem

Using the same load, reverting to otherwise identical CentOS 2.6.9 kernel without the patch, the panic is 
reproducible in minutes.
Comment 5 Dave Jones 2006-09-17 01:09:55 EDT
Fixed in CVS, will be in the next build.

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