PHP :: Bug #38268 :: zend_hash

[2006-07-31 14:40 UTC] marc dot dassonneville at gmail dot com

Description:
------------
zend_hash_find segfault when calling property of null object

I can reproduce the SEGFAULT, but can't reduce the code (code of 7KLines).

It seems that the bug occurs when an object A returns null instead of an object B,  + try to access a property of B.

Exemple :
$foo->give_me_A()->property_of_B = $bar; // crash when give_me_A() return null.

If I test that $foo->give_me_A() don't return null before doing this call, it doesn't segfault.

BUT .. I can't manage to reproduce this bug in a smaller code :/


I gave below some GDB debug.

Segfault tested on : PHP 5.1.4 (cli) (built: Jul 19 2006 12:36:47) on an old linux box (2.4.20)
It also segfault on : PHP 5.1.2 (cgi-fcgi) (built: Jul 19 2006 00:02:34) on the last KUbuntu (2.6.15)



Actual result:
--------------
GDB Result on the old linux box :

0x081e0098 in zend_std_get_method (object_ptr=0xbfffbe98, method_name=0x8374b64 "get_client", method_len=10) at /home/marc/tmp/PHP/php-5.1.4/Zend/zend_object_handlers.c:738
738             if (zend_hash_find(&zobj->ce->function_table, lc_method_name, method_len+1, (void **)&fbc) == FAILURE) {
(gdb) where
#0  0x081e0098 in zend_std_get_method (object_ptr=0xbfffbe98, method_name=0x8374b64 "get_client", method_len=10) at /home/marc/tmp/PHP/php-5.1.4/Zend/zend_object_handlers.c:738
#1  0x08218f6a in ZEND_INIT_METHOD_CALL_SPEC_CV_CONST_HANDLER (execute_data=0xbfffc9e0) at /home/marc/tmp/PHP/php-5.1.4/Zend/zend_vm_execute.h:20875
#2  0x081e28f8 in execute (op_array=0x83701b4) at /home/marc/tmp/PHP/php-5.1.4/Zend/zend_vm_execute.h:92
#3  0x081ca270 in zend_execute_scripts (type=8, retval=0x0, file_count=3) at /home/marc/tmp/PHP/php-5.1.4/Zend/zend.c:1109
#4  0x08190dc3 in php_execute_script (primary_file=0xbfffee10) at /home/marc/tmp/PHP/php-5.1.4/main/main.c:1732
#5  0x0822eea3 in main (argc=3, argv=0xbfffeec4) at /home/marc/tmp/PHP/php-5.1.4/sapi/cli/php_cli.c:1092
#6  0x400a45d9 in __libc_start_main () from /lib/libc.so.6



Some valgrind info on KUbuntu :

==32660==
==32660== Invalid read of size 4
==32660==    at 0x8282B54: (within /usr/bin/php5-cgi)
==32660==    by 0x82B5896: (within /usr/bin/php5-cgi)
==32660==    by 0x8286381: execute (in /usr/bin/php5-cgi)
==32660==    by 0x826B814: zend_execute_scripts (in /usr/bin/php5-cgi)
==32660==    by 0x822D2F7: php_execute_script (in /usr/bin/php5-cgi)
==32660==    by 0x8300285: main (in /usr/bin/php5-cgi)
==32660==  Address 0xA is not stack'd, malloc'd or (recently) free'd
==32660==
==32660== Process terminating with default action of signal 11 (SIGSEGV)
==32660==  Access not within mapped region at address 0xA
==32660==    at 0x8282B54: (within /usr/bin/php5-cgi)
==32660==    by 0x82B5896: (within /usr/bin/php5-cgi)
==32660==    by 0x8286381: execute (in /usr/bin/php5-cgi)
==32660==    by 0x826B814: zend_execute_scripts (in /usr/bin/php5-cgi)
==32660==    by 0x822D2F7: php_execute_script (in /usr/bin/php5-cgi)
==32660==    by 0x8300285: main (in /usr/bin/php5-cgi)

[2006-07-31 14:44 UTC] tony2001@php.net

Please try using this CVS snapshot:

  http://snaps.php.net/php5.2-latest.tar.gz
 
For Windows:
 
  http://snaps.php.net/win32/php5.2-win32-latest.zip

[2006-07-31 16:22 UTC] marc dot dassonneville at gmail dot com

I tried http://snaps.php.net/php5.2-latest.tar.gz

I have compiled it on 2 different box using :
  gcc 4.0.3 (Ubuntu 4.0.3-1ubuntu5)
  gcc version 3.3.2 (old linux box)
and with configure options 
  ./configure --disable-libxml --disable-dom --disable-simplexml --disable-xml --disable-xmlwriter --disable-xmlreader --without-pear --enable-sockets

I was writing you that it worked when I saw an error :(

It used to segfault after 1 sec with php 5.1.4.
Now, with the CVS snapshot, it segfault after a random time (> 10 sec, sometimes > 1 min)

It segfault both on kubuntu with a recent gcc and the old linux box with an old gcc.

On the ubuntu box, I launched it several times with Valgrind, and it ends up in different ways :

1/ 
==1202== Stack overflow in thread 1: can't grow stack to 0xBE47AFF4
==1202==
==1202== Process terminating with default action of signal 11 (SIGSEGV)
==1202==  Access not within mapped region at address 0xBE47AFF4
==1202==    at 0x81F765E: zend_objects_store_del_ref_by_handle (zend_objects_API.c:174)
==1202== Stack overflow in thread 1: can't grow stack to 0xBE47AFDC
==1202==
==1202== Process terminating with default action of signal 11 (SIGSEGV)
==1202==  Access not within mapped region at address 0xBE47AFDC
==1202==    at 0x4019308: _vgw_freeres (vg_preloaded.c:58)
==1202==
==1202== ERROR SUMMARY: 10 errors from 10 contexts (suppressed: 21 from 1)
==1202== malloc/free: in use at exit: 1,639,071 bytes in 9,876 blocks.
==1202== malloc/free: 16,722 allocs, 6,846 frees, 2,591,007 bytes allocated.
==1202== For counts of detected errors, rerun with: -v
==1202== searching for pointers to 9,876 not-freed blocks.
==1202== checked 5,609,488 bytes.

2/
==1231== Invalid write of size 4
==1231==    at 0x81C8F04: _zend_mm_alloc_int (zend_alloc.c:478)
==1231==    by 0x81C92A1: _estrndup (zend_alloc.c:1729)
==1231==    by 0x81F56CB: zend_std_object_get_class_name (zend_object_handlers.c:1062)
==1231==    by 0x81EAA38: zif_get_parent_class (zend_builtin_functions.c:607)
==1231==    by 0x81F9AA7: zend_do_fcall_common_helper_SPEC (zend_vm_execute.h:200)
==1231==    by 0x81F7C8A: execute (zend_vm_execute.h:92)
==1231==    by 0x81D42FE: zend_eval_string (zend_execute_API.c:1130)
==1231==    by 0x8186AA3: zif_assert (assert.c:152)
==1231==    by 0x81F9AA7: zend_do_fcall_common_helper_SPEC (zend_vm_execute.h:200)
==1231==    by 0x81F7C8A: execute (zend_vm_execute.h:92)
==1231==    by 0x81F963A: zend_do_fcall_common_helper_SPEC (zend_vm_execute.h:234)
==1231==    by 0x81F7C8A: execute (zend_vm_execute.h:92)
==1231==  Address 0xD is not stack'd, malloc'd or (recently) free'd
==1231==
==1231== Process terminating with default action of signal 11 (SIGSEGV)
==1231==  Access not within mapped region at address 0xD
==1231==    at 0x81C8F04: _zend_mm_alloc_int (zend_alloc.c:478)
==1231==    by 0x81C92A1: _estrndup (zend_alloc.c:1729)
==1231==    by 0x81F56CB: zend_std_object_get_class_name (zend_object_handlers.c:1062)
==1231==    by 0x81EAA38: zif_get_parent_class (zend_builtin_functions.c:607)
==1231==    by 0x81F9AA7: zend_do_fcall_common_helper_SPEC (zend_vm_execute.h:200)
==1231==    by 0x81F7C8A: execute (zend_vm_execute.h:92)
==1231==    by 0x81D42FE: zend_eval_string (zend_execute_API.c:1130)
==1231==    by 0x8186AA3: zif_assert (assert.c:152)
==1231==    by 0x81F9AA7: zend_do_fcall_common_helper_SPEC (zend_vm_execute.h:200)
==1231==    by 0x81F7C8A: execute (zend_vm_execute.h:92)
==1231==    by 0x81F963A: zend_do_fcall_common_helper_SPEC (zend_vm_execute.h:234)
==1231==    by 0x81F7C8A: execute (zend_vm_execute.h:92)

3/
==1236== Stack overflow in thread 1: can't grow stack to 0xBE3A9FF4
==1236==
==1236== Process terminating with default action of signal 11 (SIGSEGV)
==1236==  Access not within mapped region at address 0xBE3A9FF4
==1236==    at 0x81F765E: zend_objects_store_del_ref_by_handle (zend_objects_API.c:174)
==1236== Stack overflow in thread 1: can't grow stack to 0xBE3A9FDC
==1236==
==1236== Process terminating with default action of signal 11 (SIGSEGV)
==1236==  Access not within mapped region at address 0xBE3A9FDC
==1236==    at 0x4019308: _vgw_freeres (vg_preloaded.c:58)

With GDB on the old linux box :

1/
Program received signal SIGSEGV, Segmentation fault.
_zend_mm_free_int (heap=0x82fe190, p=0x0) at /home/marc/tmp/PHP/php5.2-200607311230/Zend/zend_alloc.c:477
477             prev->next_free_block = next;
(gdb) where
#0  _zend_mm_free_int (heap=0x82fe190, p=0x0) at /home/marc/tmp/PHP/php5.2-200607311230/Zend/zend_alloc.c:477
#1  0x081bfcca in _efree (ptr=0x0) at /home/marc/tmp/PHP/php5.2-200607311230/Zend/zend_alloc.c:1621
#2  0x081f592d in ZEND_ECHO_SPEC_TMP_HANDLER (execute_data=0xbfffacd0) at /home/marc/tmp/PHP/php5.2-200607311230/Zend/zend_variables.h:35
#3  0x081ee2c8 in execute (op_array=0xbfffacd0) at /home/marc/tmp/PHP/php5.2-200607311230/Zend/zend_vm_execute.h:92
#4  0x081ee838 in zend_do_fcall_common_helper_SPEC (execute_data=0xbfffb800) at /home/marc/tmp/PHP/php5.2-200607311230/Zend/zend_vm_execute.h:234
#5  0x081ee2c8 in execute (op_array=0x400a1254) at /home/marc/tmp/PHP/php5.2-200607311230/Zend/zend_vm_execute.h:92
#6  0x081d585e in zend_execute_scripts (type=8, retval=0x0, file_count=3) at /home/marc/tmp/PHP/php5.2-200607311230/Zend/zend.c:1095
#7  0x0819a2b6 in php_execute_script (primary_file=0xbfffdc10) at /home/marc/tmp/PHP/php5.2-200607311230/main/main.c:1759
#8  0x0823ae2d in main (argc=3, argv=0xbfffdcc4) at /home/marc/tmp/PHP/php5.2-200607311230/sapi/cli/php_cli.c:1097
#9  0x42017589 in __libc_start_main () from /lib/i686/libc.so.6

2/
Program received signal SIGSEGV, Segmentation fault.
0x401a2dff in ?? ()
(gdb) where
#0  0x401a2dff in ?? ()
#1  0x081ee2c8 in execute (op_array=0x401a2df8) at /home/marc/tmp/PHP/php5.2-200607311230/Zend/zend_vm_execute.h:92
#2  0x081d585e in zend_execute_scripts (type=8, retval=0x0, file_count=3) at /home/marc/tmp/PHP/php5.2-200607311230/Zend/zend.c:1095
#3  0x0819a2b6 in php_execute_script (primary_file=0xbffff590) at /home/marc/tmp/PHP/php5.2-200607311230/main/main.c:1759
#4  0x0823ae2d in main (argc=3, argv=0xbffff644) at /home/marc/tmp/PHP/php5.2-200607311230/sapi/cli/php_cli.c:1097
#5  0x42017589 in __libc_start_main () from /lib/i686/libc.so.6

[2006-07-31 17:47 UTC] tony2001@php.net

Okay, now we need a reproduce case.

[2006-08-08 01:00 UTC] php-bugs at lists dot php dot net

No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".

Patches

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