New submission from Chinh Nguyen:
I'm using ctypes to access the PAM library to change a user's password. That
is, using the function pam_chauthtok. This is occurring inside a python celery
worker in FreeBSD. This will work the first time, the second time generates a
segfault and crashes the worker.
On attaching gdb to the worker process, I observe the following:
* Crash occurs in function login_setcryptfmt
* Setting a breakpoint there, I see the following after the first successful
password change "warning: Temporarily disabling breakpoints for unloaded shared
library "/lib/libcrypt.so.5"
* When there is segfault on the second password change, the location of the
segfault cannot be disassemble
* It doesn't look like libcrypt is a direct dependency of libpam.
So it looks like what is happening is this:
* libcrypt is loaded (by python/system?) to invoke some password-related
functions, it is then unloaded (by python/system?)
* When the same function is invoked again, somehow libcrypt does not get
loaded. This results in a function call to the same function address which is
now invalid.
My current work-around is to include libcrypto explicitly by binding to it
though I don't use it directly. For example, libcrypt =
CDLL(find_library("crypt")).
Other notes:
* This does not occur if I launch celery worker all running in the same process
via the celery "green threads" module eventlet
* This only happens if the celery worker is a python child process. I don't
know how celery spawns child processes.
----------
components: ctypes
messages: 291798
nosy: Chinh Nguyen
priority: normal
severity: normal
status: open
title: Automatic Unload of Dynamic Library Cause Segfault
type: crash
versions: Python 2.7
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Python tracker <[email protected]>
<http://bugs.python.org/issue30089>
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