[Bug 898829] Re: Segfault in dlerror.c 160 on call to dlopen
Michael Owens
michael.owens at linterra.org
Thu Dec 1 22:07:35 UTC 2011
** Description changed:
I've encountered a segfault in dlerrror.c on XUbuntu 11.10 64-bit
desktop in an Apache module, specifically when one of the module's
- shared libraries called dlopen(). I have searched launchpad for likely
+ shared libraries calls dlopen(). I have searched launchpad for likely
candidates and this problem may be related to the following bugs:
https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/893605.
https://bugs.launchpad.net/ubuntu/+source/nspluginwrapper/+bug/762387
- The segfault occurs within an Apache module I wrote which embeds a Ruby
- VM via libruby, which is dynamically linked. The segfault occurs on Ruby
- startup, where it attempts to load
- /usr/lib/ruby/1.9.1/x86_64-linux/etc.so via dlopen(). This produces
- following:
+ The Apache module (which I wrote) embeds a Ruby VM via libruby, which is
+ dynamically linked. The segfault occurs on Ruby startup, where it
+ attempts to load /usr/lib/ruby/1.9.1/x86_64-linux/etc.so via dlopen().
+ This produces following:
#0 __GI___libc_free (mem=0x20000) at malloc.c:3709
#1 0x00007ffff68b2565 in _dlerror_run (operate=0x7ffff68b1ec0 <dlopen_doit>, args=0x7fffffffa530) at dlerror.c:160
#2 0x00007ffff68b1fc1 in __dlopen (file=<optimized out>, mode=<optimized out>) at dlopen.c:88
#3 0x00007ffff3f63c65 in dln_load (file=0x7ffff83e3100 "/usr/lib/ruby/1.9.1/x86_64-linux/etc.so") at dln.c:1276
#4 0x00007ffff3f9d29a in load_ext (path=140737356478000) at load.c:554
Ruby calls into dlopen.c as follows:
/* Load file */
if ((handle = (void*)dlopen(file, RTLD_LAZY|RTLD_GLOBAL)) == NULL) {
error = dln_strerror();
goto failed;
}
- This is the first call by Ruby to dlopen(), calling
- /usr/lib/ruby/1.9.1/x86_64-linux/etc.so. dlopen() then proceeds into
- dlerror() where on line 160 it attempts to free an error string in the
- result structure that has a bad memory address. This code is as follows:
+ This is the first call that Ruby makes to dlopen(). dlopen() then
+ proceeds into dlerror.c where on line 160 it attempts to free an error
+ string in a result structure that has a bad memory address. The code is
+ as follows:
if (result->errstring != NULL)
{
/* Free the error string from the last failed command. This can
happen if `dlerror' was not run after an error was found. */
if (result->malloced)
free ((char *) result->errstring); <-- dies here.
result->errstring = NULL;
}
The value of the result structure is the following:
$8 = {errcode = -131693408, returned = 32767, malloced = 192,
objname = 0x7ffff2149010 "\004", errstring = 0x20000 <Address 0x20000
out of bounds>}
- This appears to be the first DSO that Ruby attempts to load, leading me
- to suspect that that it may be related to the above bug LP bugs.
+ Since this appears to be the first DSO Ruby attempts to load, it lead me
+ to suspect that that it may be related to bug 893605 above.
- To test dlopen() on the etc.so file in particular, I added a line in the
- module calling dlopen() on it just before the Ruby initialization. This
- invocation worked without a problem. Yet when the Ruby library attempted
- it next, it caused the sefault.
+ To test the general call to dlopen() on the etc.so file in particular, I
+ added a line in the Apache module to do so just before it enters Ruby
+ initialization. This invocation of dlopen() worked without a problem.
+ Yet when the Ruby library attempted it next, it caused the above sefault
+ in dlerror.c.
Guessing that that maybe it had something to do with visibility of
symbols within Apache, I statically linked libruby it to the module in
- the hopes that dlopen() would then work. But it again produced the same
+ the hopes that dlopen() would work then. But it again produced the same
segfault.
Wondering if it could be changes in either the Ruby or Apache code, I
compiled and built the same versions of Ruby and Apache from Maverick
- (which work fine) on 11.10 to try to rule it out. They produced the
- exact same segfault in 11.10.
+ (which work fine) on 11.10 to rule this out. They produced the exact
+ same segfault in 11.10.
- I have not tested on 32 bit yet but am in the process.
+ I have not tested this on 32 bit yet but am in the process.
- With regard to the module as the culprit, I have maintained it for over
- three years without incident from Hardy up to Maverick on both 32 bit
- and 64 bit systems. It also compiles and runs on FreeBSD without
- problems.
+ With regard to the Apache module itself as the culprit, I have
+ maintained it for over three years without incident from Hardy up to
+ Maverick on both 32 bit and 64 bit systems. It also compiles and runs on
+ FreeBSD without problems. Further, I have not made any substantial
+ changes to it for the last eight months.
- The compiled binaries are located on http://mikeowens.ws/bug/. There is
- a short README file explaining how to reproduce the problem. Also, the
- full source code for the project is at https://github.com/linterra/r4a.
- It has a debian folder so it can be built via pbuilder and dpkg-
- buildpackage.
+ To reproduce the bug, I put the compiled binaries on
+ http://mikeowens.ws/bug/ along with a short README file explaining how
+ to reproduce the problem. Also, the full source code for the project is
+ at https://github.com/linterra/r4a. It has a debian folder so it can be
+ built via pbuilder and dpkg-buildpackage.
The full backtrace is attached.
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https://bugs.launchpad.net/bugs/898829
Title:
Segfault in dlerror.c 160 on call to dlopen
Status in “eglibc” package in Ubuntu:
New
Bug description:
I've encountered a segfault in dlerrror.c on XUbuntu 11.10 64-bit
desktop in an Apache module, specifically when one of the module's
shared libraries calls dlopen(). I have searched launchpad for likely
candidates and this problem may be related to the following bugs:
https://bugs.launchpad.net/ubuntu/+source/eglibc/+bug/893605.
https://bugs.launchpad.net/ubuntu/+source/nspluginwrapper/+bug/762387
The Apache module (which I wrote) embeds a Ruby VM via libruby, which
is dynamically linked. The segfault occurs on Ruby startup, where it
attempts to load /usr/lib/ruby/1.9.1/x86_64-linux/etc.so via dlopen().
This produces following:
#0 __GI___libc_free (mem=0x20000) at malloc.c:3709
#1 0x00007ffff68b2565 in _dlerror_run (operate=0x7ffff68b1ec0 <dlopen_doit>, args=0x7fffffffa530) at dlerror.c:160
#2 0x00007ffff68b1fc1 in __dlopen (file=<optimized out>, mode=<optimized out>) at dlopen.c:88
#3 0x00007ffff3f63c65 in dln_load (file=0x7ffff83e3100 "/usr/lib/ruby/1.9.1/x86_64-linux/etc.so") at dln.c:1276
#4 0x00007ffff3f9d29a in load_ext (path=140737356478000) at load.c:554
Ruby calls into dlopen.c as follows:
/* Load file */
if ((handle = (void*)dlopen(file, RTLD_LAZY|RTLD_GLOBAL)) == NULL) {
error = dln_strerror();
goto failed;
}
This is the first call that Ruby makes to dlopen(). dlopen() then
proceeds into dlerror.c where on line 160 it attempts to free an error
string in a result structure that has a bad memory address. The code
is as follows:
if (result->errstring != NULL)
{
/* Free the error string from the last failed command. This can
happen if `dlerror' was not run after an error was found. */
if (result->malloced)
free ((char *) result->errstring); <-- dies here.
result->errstring = NULL;
}
The value of the result structure is the following:
$8 = {errcode = -131693408, returned = 32767, malloced = 192,
objname = 0x7ffff2149010 "\004", errstring = 0x20000 <Address 0x20000
out of bounds>}
Since this appears to be the first DSO Ruby attempts to load, it lead
me to suspect that that it may be related to bug 893605 above.
To test the general call to dlopen() on the etc.so file in particular,
I added a line in the Apache module to do so just before it enters
Ruby initialization. This invocation of dlopen() worked without a
problem. Yet when the Ruby library attempted it next, it caused the
above sefault in dlerror.c.
Guessing that that maybe it had something to do with visibility of
symbols within Apache, I statically linked libruby it to the module in
the hopes that dlopen() would work then. But it again produced the
same segfault.
Wondering if it could be changes in either the Ruby or Apache code, I
compiled and built the same versions of Ruby and Apache from Maverick
(which work fine) on 11.10 to rule this out. They produced the exact
same segfault in 11.10.
I have not tested this on 32 bit yet but am in the process.
With regard to the Apache module itself as the culprit, I have
maintained it for over three years without incident from Hardy up to
Maverick on both 32 bit and 64 bit systems. It also compiles and runs
on FreeBSD without problems. Further, I have not made any substantial
changes to it for the last eight months.
To reproduce the bug, I put the compiled binaries on
http://mikeowens.ws/bug/ along with a short README file explaining how
to reproduce the problem. Also, the full source code for the project
is at https://github.com/linterra/r4a. It has a debian folder so it
can be built via pbuilder and dpkg-buildpackage.
The full backtrace is attached.
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