XPost: linux.debian.bugs.dist

Note: Only crashes if libnss-myhostname is installed.

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XPost: linux.debian.bugs.dist

control: retitle -1 Bug#872727: libc6-dev: gethostbyname segfaults with libnss_resolve.so.2 for static binaries
control: tag -1 + upstream
control: forwarded https://sourceware.org/bugzilla/show_bug.cgi?id=21975

On 2017-08-20 17:02, Horst Schirmeier wrote:

Package: libc6-dev
Version: 2.24-11+deb9u1
Severity: normal

Dear Maintainer,

with glibc 2.24 (reproducible on 64-bit Debian 9 or Ubuntu 17.04), gethostbyname() always segfaults if the binary was linked statically:

$ echo -e "#include <netdb.h>\nint main(void){gethostbyname(\"foo\");}" >foo.c && \
gcc -g -static foo.c && ./a.out
/tmp/ccp8JNGC.o: In function `main':
/tmp/foo.c:2: warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
Segmentation fault
$ gdb a.out
GNU gdb (Debian 7.12-6) 7.12.0.20161007-git
[...]
Reading symbols from a.out...done.
(gdb) run
Starting program: /tmp/a.out
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt
#0 0x0000000000000000 in ?? ()
#1 0x00007ffff72ac040 in __pthread_initialize_minimal_internal () at nptl-init.c:460
#2 0x00007ffff72ab5e1 in _init () at ../sysdeps/x86_64/crti.S:72
#3 0x00007ffff76cc830 in ?? () from /lib/x86_64-linux-gnu/libnss_myhostname.so.2
#4 0x0000000000478a7a in call_init.part ()
#5 0x0000000000478c35 in _dl_init ()
#6 0x000000000047089e in dl_open_worker ()
#7 0x000000000046e0f4 in _dl_catch_error ()
#8 0x000000000047024c in _dl_open ()
#9 0x0000000000439ba2 in do_dlopen ()
#10 0x000000000046e0f4 in _dl_catch_error ()
#11 0x0000000000439bd7 in dlerror_run ()
#12 0x0000000000439da3 in __libc_dlopen_mode ()
#13 0x0000000000436b3b in __nss_lookup_function ()
#14 0x0000000000436d45 in __nss_next2 ()
#15 0x000000000043504a in gethostbyname_r ()
#16 0x0000000000434d93 in gethostbyname ()
#17 0x0000000000400b2e in main () at foo.c:2

As said in the upstream bug report, it's because you are using
libnss-resolve or libnss-myhostname, which are linked with libpthread.
The workaround is to not install those packages or to disable them in /etc/nsswitch.conf.

In my upstream bug report, a commenter noted that this weren't reproducible in
Fedora's glibc 2.24 or 2.25, suggesting this "could be a Debian or Ubuntu patch": https://sourceware.org/bugzilla/show_bug.cgi?id=21975

I am perfectly able to reproduce the issue on a fedora system, which
installs libnss-myhostname by default.

--
Aurelien Jarno GPG: 4096R/1DDD8C9B aurelien@aurel32.net http://www.aurel32.net

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XPost: linux.debian.bugs.dist

Package: libc6-dev
Version: 2.24-11+deb9u1
Severity: normal

Dear Maintainer,

with glibc 2.24 (reproducible on 64-bit Debian 9 or Ubuntu 17.04), gethostbyname() always segfaults if the binary was linked statically:

$ echo -e "#include <netdb.h>\nint main(void){gethostbyname(\"foo\");}" >foo.c && \
gcc -g -static foo.c && ./a.out
/tmp/ccp8JNGC.o: In function `main':
/tmp/foo.c:2: warning: Using 'gethostbyname' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
Segmentation fault
$ gdb a.out
GNU gdb (Debian 7.12-6) 7.12.0.20161007-git
[...]
Reading symbols from a.out...done.
(gdb) run
Starting program: /tmp/a.out
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt
#0 0x0000000000000000 in ?? ()
#1 0x00007ffff72ac040 in __pthread_initialize_minimal_internal () at nptl-init.c:460
#2 0x00007ffff72ab5e1 in _init () at ../sysdeps/x86_64/crti.S:72
#3 0x00007ffff76cc830 in ?? () from /lib/x86_64-linux-gnu/libnss_myhostname.so.2
#4 0x0000000000478a7a in call_init.part ()
#5 0x0000000000478c35 in _dl_init ()
#6 0x000000000047089e in dl_open_worker ()
#7 0x000000000046e0f4 in _dl_catch_error ()
#8 0x000000000047024c in _dl_open ()
#9 0x0000000000439ba2 in do_dlopen ()
#10 0x000000000046e0f4 in _dl_catch_error ()
#11 0x0000000000439bd7 in dlerror_run ()
#12 0x0000000000439da3 in __libc_dlopen_mode ()
#13 0x0000000000436b3b in __nss_lookup_function ()
#14 0x0000000000436d45 in __nss_next2 ()
#15 0x000000000043504a in gethostbyname_r ()
#16 0x0000000000434d93 in gethostbyname ()
#17 0x0000000000400b2e in main () at foo.c:2

In my upstream bug report, a commenter noted that this weren't reproducible in Fedora's glibc 2.24 or 2.25, suggesting this "could be a Debian or Ubuntu patch": https://sourceware.org/bugzilla/show_bug.cgi?id=21975

-- System Information:
Debian Release: 9.1
APT prefers stable
APT policy: (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.9.0-3-amd64 (SMP w/64 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages libc6-dev depends on:
ii libc-dev-bin 2.24-11+deb9u1
ii libc6 2.24-11+deb9u1
ii linux-libc-dev 4.9.30-2+deb9u3

libc6-dev recommends no packages.

Versions of packages libc6-dev suggests:
pn glibc-doc <none>
ii manpages-dev 4.10-2

-- no debconf information

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