Bug 199891 - [patch] 'vmstat -i' output is wrong on RPi
Summary: [patch] 'vmstat -i' output is wrong on RPi
Status: Closed FIXED
Alias: None
Product: Base System
Classification: Unclassified
Component: bin (show other bugs)
Version: CURRENT
Hardware: Any Any
: --- Affects Many People
Assignee: freebsd-bugs (Nobody)
Depends on:
Reported: 2015-05-03 16:21 UTC by Jia-Shiun Li
Modified: 2015-05-17 13:51 UTC (History)
1 user (show)

See Also:

original 'vmstat -i' output on RPi (15.32 KB, text/plain)
2015-05-03 16:21 UTC, Jia-Shiun Li
no flags Details
patch to vmstat.c (454 bytes, patch)
2015-05-03 16:24 UTC, Jia-Shiun Li
no flags Details | Diff

Note You need to log in before you can comment on or make changes to this bug.
Description Jia-Shiun Li 2015-05-03 16:21:01 UTC
Created attachment 156288 [details]
original 'vmstat -i' output on RPi

'vmstat -i' output is wrong on RPi. (See attached file)

The cause is in sufficient check for end of intrnames in dointr(). It only looks for zero-length string as end of buffer. But on every architecture FreeBSD supports, intrnames are all initialized to array of strings of 19 spaces plus NUL in kernel. The check will always make intrname run over the end of buffer.

x86 does not see this probably due to implementation of memory allocator. On arch like RPi, vmstat did not encounter immediate consecutive \0s to be intepreted as zero-length string. Thus it treated data after the buffer as long interrupt names.
Comment 1 Jia-Shiun Li 2015-05-03 16:24:29 UTC
Created attachment 156290 [details]
patch to vmstat.c

Add boundary check to intrnames in dointr().

But probably kernel & user space need to agree on how to treat the buffer safely.
Comment 2 commit-hook freebsd_committer 2015-05-13 02:26:47 UTC
A commit references this bug:

Author: loos
Date: Wed May 13 02:25:54 UTC 2015
New revision: 282829
URL: https://svnweb.freebsd.org/changeset/base/282829

  Fix the vmstat -i output on ARM.

  The consumers of hw.intrnames expect a NULL byte at end of the string
  containing the interrupt names.

  On ARM all the interrupt name slots are initialized and this leave no room
  for the terminating NULL byte, which makes vmstat read beyond the end of

  PR:		199891
  Tested on:	RPi 2 and BeagleBone Black