Re: free(): double free detected in tcache 2

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On 26/02/2020 11:18, Graham Cobb wrote:
> After upgrading to dar 2.6.8 I seem to have hit a (different) bug. 
> My daily backup now fails with:
> 
> free(): double free detected in tcache 2
> 
> So far it has only tried once, and has hit that error. However, I 
> have never seen it before, and this is the first backup since I 
> upgraded from dar 2.6.6 yesterday.

Looking a the difference in dar/libdar between 2.6.6 and 2.6.8 I
cannot seen any alocation related thing, nor any modification in when
calling
external libraries...

Difficult to know what caused this without more info

How did you upgrade from 2.6.6 to 2.6.8?
- - was it through distro package upgrade?
- - did you grab the source code and compiled dar yourself?

both way are valid, the impact are different on libraries dar relies on:
- - in the first case you may have also upgraded some libraries
- - in the second case you have not

> 
> I will try to reproduce it, but are there any additional options 
> you suggest I turn on to get any more information about the problem
> (assuming it recurs)?

I would recompile dar activating debugging information
export CXXFLAGS=-g
export LDFLAGS=-g
export CFLAGS=-g
./configure --prefix=... etc.
make
make uninstall (if you want to remove the old installed dar/libdar
binaries)
make install (and not "make install-strip" which would remove all
symbols including debugging ones)


If you have already a core file, I could try to have a look at it with
gdb, not sure I can get much of it without debugging symbols... but it
worth trying

> 
> Here is the actual log from last night's DAR_automatic_backup.sh 
> run (note: I have removed a LONG list of -P options to protect the
>  filesystem information as I am posting this to a public list)...
> 
> ############ DARsystem: ### Wed, 26 Feb 2020 02:20:02 +0000 ### 
> DARsystem: Current backup information (Size in 1024 bytes blocks.):
> DARsystem: ..DARsystemFull: 36509724. DARsystem: ..DARsystemDiff:
> 3198896: DARsystem: ....DARsystemDiff01: 3198896. ############
> DARsystem: Preparing to Create DARsystemDiff02. ############
> DARsystem: creating DARsystemDiff02. Please wait. ### No terminal
> found for user interaction. All questions will be assumed a
> negative answer (less destructive choice), which most of the time
> will abort the program. free(): double free detected in tcache 2
> sh: line 1: 108460 Aborted                 dar -s 1450M -c
> /backup/DAR/novatech/DARsystemDiff02 -A 
> /backup/DAR/novatech/DARsystemDiff01 -R / --compression=bzip2:9 -m 
> 0 -D -N --retry-on-change 20 --alter=secu -P "backup" <LOTS OF 
> OTHER -P OPTIONS REMOVED> -X ".xsession-errors" -X "stderrdae.txt" 
> -X "stdoutdae.txt" -X "client_state.xml" -X "stderrgui.txt" -X 
> "stderr.txt" -X "xaakg.out" -X "tmp2" -Z "*.dar" -Z "*.crypt" -Z 
> "*.arj" -Z "*.bz2" -Z "*.bz" -Z "*.Z" -Z "*.tgz" -Z "*.taz" -Z 
> "*.cpio" -Z "*.deb" -Z "*.gtar" -Z "*.gz" -Z "*.lzh" -Z "*.lhz" -Z 
> "*.rar" -Z "*.rpm" -Z "*.shar" -Z "*.sv4cpi" -Z "*.sv4crc" -Z 
> "*.tar" -Z "*.ustar" -Z "*.zoo" -Z "*.zip" -Z "*.jar" -Z "*.jpg"
> -Z "*.gif" -Z "*.mpg" -Z "*.mpeg" -Z "*.avi" -Z "*.ram" -Z "*.rm"
> -Z "*.mp3" DARsystem: Sorry. 'dar' failed with exit code 134. 
> DARsystemDiff02 backup aborted. ############
> 

By the way have you tried the workaround I suggested for the testing
phase (not using --sequential-read and relying on an isolated catalog)?




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