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init script broken due to bash vs sh syntax #6

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deadlysyn opened this issue Jul 15, 2017 · 1 comment
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init script broken due to bash vs sh syntax #6

deadlysyn opened this issue Jul 15, 2017 · 1 comment

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@deadlysyn
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ran into this on ubuntu trusty but really more of a portable shell gotcha.

/bin/sh on linux is just a special case of /bin/bash as you know, but only enables a subset of bash functionality when called as /bin/sh.

in atop.init your shebang uses /bin/sh but uses a bashism on line 50 (let CNT+=1). i've tested this two ways, whichever you prefer to fix it:

  1. change the let line to be "CNT=expr $CNT + 1"
  2. change atop.init to use /bin/bash (probably better for consistency, since you use /bin/bash elsewhere?)

without one of these, you will get log spam about that syntax on each run/restart.

hth
@Atoptool
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You are right about this! Since bash is used by other scripts as well, I modified /bin/sh to /bin/bash.

zlandau added a commit to zlandau/atop that referenced this issue Feb 16, 2020
@zlandau
Fix crash when system reports huge load averages
f202a31 
The load average reporting functions in showsys.c use static buffer
sizes. When the load averages on a machine are very large, this causes
the writes to extend past the buffer. With this commit, if a number is
too large then we just show '>NNNNNN'. I'm not sure if this is the best
choice, so I'm open to other ideas.

This is what the output looks like when we exceed the maximums:

  CPL | avg1 >999999 | avg5 >999999 | avg15 >99999 | csw 103117e3 | intr 88296e3 |

Note that this was triggered from a kernel that is reporting clearly
inaccurate numbers:

  $ cat /proc/loadavg
  1.25 2.40 368567045.47 1/589 53576

But regardless, crashing is no fun.

For future reference, I narrowed down the issue by building with
-fsanitize=address. For example:

  ==55396==ERROR: AddressSanitizer: global-buffer-overflow on address 0x55c527d6f14f at pc 0x7f4729942df9 bp 0x7ffe1fd30710 sp 0x7ffe1fd2fea0
  WRITE of size 10 at 0x55c527d6f14f thread T0
      #0 0x7f4729942df8 in __interceptor_vsprintf /build/gcc/src/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:1627
      Atoptool#1 0x7f47299432cf in __interceptor_sprintf /build/gcc/src/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:1670
      Atoptool#2 0x55c527d1c167 in sysprt_CPLAVG15 (/home/kapheine/projects/atop/atop+0x74167)
      Atoptool#3 0x55c527d2087a in showsysline (/home/kapheine/projects/atop/atop+0x7887a)
      Atoptool#4 0x55c527d1471f in prisyst (/home/kapheine/projects/atop/atop+0x6c71f)
      Atoptool#5 0x55c527d090ff in generic_samp (/home/kapheine/projects/atop/atop+0x610ff)
      Atoptool#6 0x55c527ce17c9 in main (/home/kapheine/projects/atop/atop+0x397c9)
      Atoptool#7 0x7f472952a022 in __libc_start_main (/usr/lib/libc.so.6+0x27022)
      Atoptool#8 0x55c527ce266d in _start (/home/kapheine/projects/atop/atop+0x3a66d)

  0x55c527d6f14f is located 49 bytes to the left of global variable 'buf' defined in 'showsys.c:981:54' (0x55c527d6f180) of size 15
  0x55c527d6f14f is located 0 bytes to the right of global variable 'buf' defined in 'showsys.c:1000:54' (0x55c527d6f140) of size 15
@zlandau zlandau mentioned this issue Feb 16, 2020
Merged
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@deadlysyn @Atoptool