pstack causes a coredump in getexecpath ().

[blackwater]

A coredump of pstack is being analyzed by our team:

#7  0x4000000000023da0:0 in getexecpath () at getexecpath.c:211
#8  0x4000000000022230:0 in pstack () at pstack.c:952
#9  0x40000000000216d0:0 in main () at pstack.c:1401

There is a call to free() at getexecpath.c:211 and it results in a coredump.  Is it possible that some kind of buffer overflow happens in this line: getexecpath.c:211 inside pstack?

[Dennis Handly]

>There is a call to free at getexecpath.c:211 and it results in a coredump.

You should have left the free line in the stacktrace.

>Is it possible that some kind of buffer overflow happens in this line: getexecpath.c:211 inside pstack?

No, it's worst that that.  :-(

Please contact Support and file a bug report.  You can have them contact me for details.

[blackwater]

It seems that I managed to find a problem in HP pstack with HP gdb.

So I run "gdb pstack" and then set "set heap-check on". Then I do "run <PID>". And after that I get sometimes RTC_BAD_FREE. It means that pstack calls free and passes it an unallocated or already freed object!

As one can see from "info shared" below I use only HP libraries and HP utilities:

(gdb) show heap-check
Thread debugging commands is "on".
Current heap check settings are :
        Check leaks      : on
        Check bounds     : on
        Check free()     : on
        Check string     : off
        Scrambling       : off
        Frame count      : 12
        Min-leak-size    : 0
        Min-heap-size    : 0
        Block-size       : 0
        Header-size      : 16
        Footer-size      : 1
        Seed-value       : 5
        Random-range     : 100
        Null-check       : -1
        Null-check-size  : -1
        Heap-size        : 0
        Heap Interval    : 0
        Repeat Count     : 100
        High-mem Count   : 0
        Watch Address    : 0x00000000
        retain-freed-blocks : off
(gdb) r 1772
Starting program: /usr/ccs/bin/pstack 1772
warning: Attempt to free unallocated or already freed object at 0x9fffffffffffda20
__rtc_event (ecode=RTC_BAD_FREE, pointer=0x9fffffffffffda20, pclist=0x0,
    size=0) at ../../../Src/gnu/gdb/infrtc.c:2145
2145    ../../../Src/gnu/gdb/infrtc.c: No such file or directory.
        in ../../../Src/gnu/gdb/infrtc.c
(gdb) bt
#0  __rtc_event (ecode=RTC_BAD_FREE, pointer=0x9fffffffffffda20, pclist=0x0,
    size=0) at ../../../Src/gnu/gdb/infrtc.c:2145
#1  0x9fffffffff6022b0:0 in rtc_record_free (pointer=<not available>,
    free_the_block=<not available>, is_realloc=<not available>)
    at ../../../Src/gnu/gdb/infrtc.c:3968
#2  0x9fffffffff604d20:0 in free (p=0x9fffffffffffda20)
    at ../../../Src/gnu/gdb/infrtc.c:4484
#3  0x4000000000023da0:0 in getexecpath () at getexecpath.c:211
#4  0x4000000000022230:0 in pstack () at pstack.c:952
#5  0x40000000000216d0:0 in main () at pstack.c:1401
(gdb) info sharedlibrary
Shared Object Libraries
        tstart              tend              dstart              dend               gp
/usr/lib/hpux64/dld.so
0x9fffffffff640000 0x9fffffffff6f95f0 0x9fffffffff63a000 0x9fffffffff63fa38 0x9fffffffff63cf30
/opt/langtools/lib/hpux64/librtc.so
0x9fffffffff5c8000 0x9fffffffff632690 0x9fffffffff4e2000 0x9fffffffff5c7958 0x9fffffffff554968
/usr/lib/hpux64/libunwind.so.1
0x9fffffffff478000 0x9fffffffff4df410 0x9fffffffff6fe000 0x9fffffffff6fed68 0x9fffffffff6fe9e0
/usr/lib/hpux64/libuca.so.1
0x9fffffffff46c000 0x9fffffffff474020 0x9fffffffff633000 0x9fffffffff633150 0x9fffffffff633128
/usr/lib/hpux64/libc.so.1
0x9fffffffff100000 0x9fffffffff3b9ba0 0x9fffffffff453000 0x9fffffffff4692b8 0x9fffffffff45ce98
/usr/lib/hpux64/libcl.so.1
0x9fffffffff4e1000 0x9fffffffff4e150c 0x9fffffffff4e0000 0x9fffffffff4e0018 0x9fffffffff4e0010
/usr/lib/hpux64/libCsup.so.1
0x9fffffffff3ec000 0x9fffffffff44af80 0x9fffffffff3e4000 0x9fffffffff3ea3d8 0x9fffffffff3e96a8
/usr/lib/hpux64/libdl.so.1
0x9fffffffff3dc000 0x9fffffffff3e03b0 0x9fffffffff477000 0x9fffffffff4774f0 0x9fffffffff4770e8
/usr/lib/hpux64/libIO77.so.1
0x9ffffffffef24000 0x9fffffffff0ff2f0 0x9fffffffff3c2000 0x9fffffffff3db978 0x9fffffffff3ce738
Total of 9 shared libraries.

[blackwater]

Just to clarify. At first I ran pstack with TCMalloc. TCMalloc::free() coredumps in case it gets a pointer that has not been allocated before. HP libc allocator and HP MallocNG allocator do not cause a coredump with pstack. Nevertheless when I run HP pstack under HP gdb with "set heap-check on " I get RTC_BAD_FREE. So there is undefined behavior in HP pstack.

[Dennis Handly · Accepted solution]

>So there is an undefined behavior in HP pstack.

That's correct.  :-(  There is a bogus call to free.

[ShridharJoshi]

Reproduced this issue in pstack. As Dennis sugested Please contact Support and file a bug report.