NetBSD Problem Report #56080

From hauke@Espresso.Rhein-Neckar.DE  Sun Mar 28 10:01:20 2021
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Date: Sun, 28 Mar 2021 12:01:05 +0200 (CEST)
From: Hauke Fath <hauke@Espresso.Rhein-Neckar.DE>
Reply-To: Hauke Fath <hauke@Espresso.Rhein-Neckar.DE>
Cc: Hauke Fath <hauke@Espresso.Rhein-Neckar.DE>
Subject: tar(1) dumps core on nfs volume
X-Send-Pr-Version: 3.95

>Number:         56080
>Category:       bin
>Synopsis:       tar(1) dumps core on nfs volume
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lukem
>State:          feedback
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Mar 28 10:05:00 +0000 2021
>Last-Modified:  Sat Jun 10 16:05:01 +0000 2023
>Originator:     Hauke Fath
>Release:        NetBSD 9.99.81
Falling Raindrops

System: NetBSD i386-pxe 9.99.81 NetBSD 9.99.81 (BLACKBOX-$Revision: 1.85 $) #0: Mon Mar 22 16:48:50 CET 2021 amd64
Architecture: x86_64
Machine: amd64

% ldd /bin/tar
	-larchive.4 => /usr/lib/
	-lbz2.1 => /usr/lib/
	-lc.12 => /lib/
	-lcrypto.14 => /lib/
	-lcrypt.1 => /lib/
	-lexpat.2 => /usr/lib/
	-llzma.2 => /lib/
	-lpthread.1 => /lib/
	-lz.1 => /lib/
% ident /bin/tar
     $NetBSD: crt0.S,v 1.4 2018/11/26 17:37:46 joerg Exp $
     $NetBSD: crt0-common.c,v 1.23 2018/12/28 20:12:35 christos Exp $
     $NetBSD: crti.S,v 1.1 2010/08/07 18:01:35 joerg Exp $
     $NetBSD: crtbegin.S,v 1.2 2010/11/30 18:37:59 joerg Exp $
     $NetBSD: crtend.S,v 1.1 2010/08/07 18:01:34 joerg Exp $
     $NetBSD: crtn.S,v 1.1 2010/08/07 18:01:35 joerg Exp $


Building (packaging) editors/xemacs-nox11 on a net-booted -current
installation fails when libarchive-as-tar invoked from
work/xemacs-21.4.24/Makefile dumps core because of an assertion

[hauke@i386-pxe] /<6>xemacs-21.4.24/lisp > pwd
[hauke@i386-pxe] /<6>xemacs-21.4.24/lisp > tar -cf /dev/null .
Segmentation fault (core dumped)
[hauke@i386-pxe] /<6>xemacs-21.4.24/lisp > gdb /bin/tar tar.core
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Reading symbols from /bin/tar...
Reading symbols from /usr/libdata/debug//bin/tar.debug...
[New process 6101]
Core was generated by `tar'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00006f8f68467866 in _citrus_iconv_convert (nresults=0x7f7fff388ab8, flags=0, outbytes=0x7f7fff388b38, out=0x7f7fff388b30, 
    inbytes=0x7f7fff388b28, in=0x7f7fff388b20, cv=0x6f8f6a89b0e0) at /usr/src/lib/libc/citrus/citrus_iconv.h:61
61		_DIAGASSERT(cv && cv->cv_shared && cv->cv_shared->ci_ops &&
(gdb) bt
#0  0x00006f8f68467866 in _citrus_iconv_convert (nresults=0x7f7fff388ab8, flags=0, outbytes=0x7f7fff388b38, out=0x7f7fff388b30, 
    inbytes=0x7f7fff388b28, in=0x7f7fff388b20, cv=0x6f8f6a89b0e0) at /usr/src/lib/libc/citrus/citrus_iconv.h:61
#1  _iconv (handle=handle@entry=0x6f8f6a89b0e0, in=in@entry=0x7f7fff388b20, szin=szin@entry=0x7f7fff388b28, out=out@entry=0x7f7fff388b30, 
    szout=szout@entry=0x7f7fff388b38) at /usr/src/lib/libc/iconv/iconv.c:97
#2  0x00006f8f6a483834 in iconv_strncat_in_locale (as=0x6f8f6a832158, _p=<optimized out>, length=<optimized out>, sc=0x6f8f6a883070)
    at /usr/src/external/bsd/libarchive/dist/libarchive/archive_string.c:2039
#3  0x00006f8f6a4844ba in archive_strncat_l (as=as@entry=0x6f8f6a832158, _p=<optimized out>, n=<optimized out>, sc=<optimized out>)
    at /usr/src/external/bsd/libarchive/dist/libarchive/archive_string.c:1998
#4  0x00006f8f6a48459a in archive_strncpy_l (as=as@entry=0x6f8f6a832158, _p=<optimized out>, n=<optimized out>, sc=<optimized out>)
    at /usr/src/external/bsd/libarchive/dist/libarchive/archive_string.c:1944
#5  0x00006f8f6a4847d9 in archive_mstring_get_mbs_l (aes=0x6f8f6a832110, p=0x7f7fff388c58, length=0x7f7fff388c88, sc=<optimized out>)
    at /usr/src/external/bsd/libarchive/dist/libarchive/archive_string.c:4005
#6  0x00006f8f6a47b810 in _archive_entry_pathname_l (entry=<optimized out>, p=<optimized out>, len=<optimized out>, sc=<optimized out>)
    at /usr/src/external/bsd/libarchive/dist/libarchive/archive_entry.c:598
#7  0x00006f8f6a41f051 in get_entry_pathname (a=0x6f8f6a88d000, entry=<optimized out>, name=<optimized out>, length=<optimized out>, 
    sc=<optimized out>) at /usr/src/external/bsd/libarchive/dist/libarchive/archive_write_set_format_pax.c:428
#8  0x00006f8f6a41f5da in archive_write_pax_header (a=0x6f8f6a88d000, entry_original=0x6f8f6a831500)
    at /usr/src/external/bsd/libarchive/dist/libarchive/archive_write_set_format_pax.c:839
#9  0x00006f8f6a46a1da in _archive_write_header (_a=0x6f8f6a88d000, entry=0x6f8f6a831500)
    at /usr/src/external/bsd/libarchive/dist/libarchive/archive_write.c:650
#10 0x00000000e4c08ac2 in write_entry (bsdtar=bsdtar@entry=0x7f7fff389590, a=a@entry=0x6f8f6a88d000, entry=0x6f8f6a831500)
    at /usr/src/external/bsd/libarchive/dist/tar/write.c:974
#11 0x00000000e4c08cac in write_file (entry=<optimized out>, a=0x6f8f6a88d000, bsdtar=0x7f7fff389590)
    at /usr/src/external/bsd/libarchive/dist/tar/write.c:962
#12 write_hierarchy (bsdtar=bsdtar@entry=0x7f7fff389590, a=a@entry=0x6f8f6a88d000, path=path@entry=0x7f7fff389dd2 ".")
    at /usr/src/external/bsd/libarchive/dist/tar/write.c:941
#13 0x00000000e4c0907e in write_archive (a=a@entry=0x6f8f6a88d000, bsdtar=bsdtar@entry=0x7f7fff389590)
    at /usr/src/external/bsd/libarchive/dist/tar/write.c:513
#14 0x00000000e4c098a4 in tar_mode_c (bsdtar=bsdtar@entry=0x7f7fff389590) at /usr/src/external/bsd/libarchive/dist/tar/write.c:247
#15 0x00000000e4c0ba4d in main (argc=<optimized out>, argv=<optimized out>) at /usr/src/external/bsd/libarchive/dist/tar/bsdtar.c:910
(gdb) print *cv
$1 = {cv_shared = 0x6c652e73, cv_closure = 0x6f8f6a80b050}
(gdb) print *cv->cv_shared
Cannot access memory at address 0x6c652e73

where 0x6c652e73 happens to be ascii 's.el'.

See also
<> ff.


	On a net-booted instance of -current amd64, with pkgsrc
	mounted r/o and WRKOBJDIR=/var/obj/pkgsrc, 'make extract'

	Change to
	${WRKOBJDIR}/editors/xemacs-nox11/work/xemacs-21.4.24/lisp and
	run '/bin/tar -cf /dev/null .'.

	The assertion failure appears to be somewhat specific to the
	tared up directory.

	/bin/pax works here, as does pkgsrc gtar.


	None, yet. 

	A workaround is to have the xemacs Makefile use GNU tar	instead.


From: RVP <rvp@SDF.ORG>
Subject: Re: bin/56080: tar(1) dumps core on nfs volume
Date: Wed, 31 Mar 2021 21:33:35 +0000 (UTC)

 Fix here:


Responsible-Changed-From-To: bin-bug-people->lukem
Responsible-Changed-When: Sun, 28 May 2023 19:52:15 +0000

State-Changed-From-To: open->analyzed
State-Changed-When: Sun, 28 May 2023 19:52:15 +0000

I read the thread about this issue, including RVP's proposed fix to
ensure that the struct filesystem.name_max field isn't 0 to fallback

I think libarchive's implementation for NetBSD could be simplified to
just allocate the backing store for sizeof(struct dirent) when using
readdir_r() on platforms where dirent.d_name has a known size (e.g.,
d_name).  Or use the existing logic modified to check at startup to use
NAME_MAX if defined and pathconf as a fallback?

(I see that macOS/Darwin and Linux/glibc both claim readdir_r() is
deprecated because NAME_MAX may be undefined, but NetBSD doesn't claim
that it's deprecated, and AFAICT, neither does POSIX.1-2017).

Looking into more detail in how libarchive uses the filesystem.name_max field:

- Relevant parts of struct filesystem:
        struct filesystem {
        // ...
        #if defined(USE_READDIR_R)
                size_t          name_max;
        // ...

- There's a lot of system-specific complexity to determine name_max
  as the length of a path name.

- Relevant parts of struct tree:
        struct tree {
        #if defined(USE_READDIR_R)
                struct dirent           *dirent;
                size_t                   dirent_allocated;

- In tree_dir_next_posix(), filesystem.name_max is used to determine
  how much space to allocate for struct tree.dirent:
        #if defined(USE_READDIR_R)
                dirent_size = offsetof(struct dirent, d_name) +
                  t->filesystem_table[t->current->filesystem_id].name_max + 1;
                if (t->dirent == NULL || t->dirent_allocated < dirent_size) {
                        t->dirent = malloc(dirent_size);

Why does libarchive go to so much effort to determine how much space to
use for the backing store for readdir_r()'s struct dirent in a
system-specific manner?

Why isn't libarchive just allocating sizeof(struct dirent) for those
systems where struct dirent is known to be a fixed size (where
dirent.d_name is fixed), and avoid this complicated
per-current-filesystem statvfs (etc) logic?

It strikes me that this complex logic could potentially fail with memory
overruns if a kernel returns the wrong value for "maximum length of a
path for that filesystem", and given dirent has a fixed upper size at
compile time on most platforms (see above).

From: "Luke Mewburn" <>
Subject: PR/56080 CVS commit: src/external/bsd/libarchive/dist/libarchive
Date: Sat, 10 Jun 2023 12:46:32 +0000

 Module Name:	src
 Committed By:	lukem
 Date:		Sat Jun 10 12:46:32 UTC 2023

 Modified Files:
 	src/external/bsd/libarchive/dist/libarchive: archive_read_disk_posix.c

 Log Message:
 libarchive: fail if name_max is 0

 Add error handling to the USE_READDIR_R code paths that set name_max
 from struct statfs or statvfs; if the determined name_max == 0
 then return an error.

 Avoids a crash in tree_dir_next_posix() when the calculation of
 dirent_size from name_max is too small for the memory allocated
 for struct dirent.

 Submitted to upstream in pull request

 Should fix PR bin/56080

 To generate a diff of this commit:
 cvs rdiff -u -r1.2 -r1.3 \

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: analyzed->feedback
State-Changed-When: Sat, 10 Jun 2023 16:02:03 +0000
Does my recent commit to -current fix this crash
(tar should fail with an error instead of crashing)

From: Luke Mewburn <>
	Hauke Fath <>
Subject: Re: bin/56080 (tar(1) dumps core on nfs volume)
Date: Sun, 11 Jun 2023 02:00:52 +1000

 I've added error handling in libarchive to error out
 if name_max==0, to avoid crashing.

 I've also submitted a pull request to the libarchive upstream
 with the same fix:

 If upstream revises the fix, I'll backport it here
 (or we'll get when we upgrade to a release that contains it).


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