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[2016-09-25 23:15 UTC] stas@php.net
-Status: Open
+Status: Feedback
[2016-09-25 23:15 UTC] stas@php.net
[2016-09-26 12:34 UTC] nguyenluan dot vnn at gmail dot com
-Status: Feedback
+Status: Open
[2016-09-26 12:34 UTC] nguyenluan dot vnn at gmail dot com
[2016-09-26 19:17 UTC] stas@php.net
-Status: Open
+Status: Duplicate
[2016-09-26 19:17 UTC] stas@php.net
[2016-09-26 19:17 UTC] stas@php.net
[2016-09-27 08:22 UTC] nguyenluan dot vnn at gmail dot com
[2016-10-19 14:19 UTC] nguyenluan dot vnn at gmail dot com
[2016-10-19 14:25 UTC] kaplan@php.net
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Last updated: Tue Nov 04 05:00:01 2025 UTC |
Description: ------------ In dom_document_savexml function: } else { if (options & LIBXML_SAVE_NOEMPTYTAG) { saveempty = xmlSaveNoEmptyTags; xmlSaveNoEmptyTags = 1; } /* Encoding is handled from the encoding property set on the document */ xmlDocDumpFormatMemory(docp, &mem, &size, format); if (options & LIBXML_SAVE_NOEMPTYTAG) { xmlSaveNoEmptyTags = saveempty; } if (!size) { RETURN_FALSE; } RETVAL_STRINGL(mem, size, 1); xmlFree(mem); } If size != 0, a string will be retured. When running the PHP test script below, variable "size" is larger than INTMAX while variable "mem" in RETVAL_STRINGL(mem, size, 1) is NULL which leads to a memory access violation when RETVAL_STRINGL calls to memcpy later. If *mem is not NULL, a string with size > 2GB is returned. This is also considered as security issue in PHP. Test script: --------------- <?php ini_set('memory_limit', -1); $str = str_repeat('a', 0x5fffffff); $doc = new DOMDocument('1.0'); $doc->formatOutput = True; $root = $doc->createElement("test1"); $root = $doc->appendChild($root); $text1 = $doc->createTextNode($str); $text1 = $root->appendChild($text1); $root = $doc->createElement("test2"); $root = $doc->appendChild($root); $text2 = $doc->createTextNode($str); $text2 = $root->appendChild($text2); $str1 = $doc->saveXML(); var_dump(strlen($str)); var_dump(strlen($str1)); ?> Expected result: ---------------- No crash, no string return since XML string input is larger than 2Gb. Actual result: -------------- gdb-peda$ b document.c:1798 Breakpoint 1 at 0x618090: file /home/user/Desktop/php-5.6.26/ext/dom/document.c, line 1798. gdb-peda$ r ../test/string/test_domxml.php Starting program: /home/user/Desktop/php-5.6.26/sapi/cli/php ../test/string/test_domxml.php [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". [----------------------------------registers-----------------------------------] RAX: 0x80000008 RBX: 0xa93d73 (<execute_ex>: push rbp) RCX: 0x7ffff4422e00 (<__mmap+64>: ja 0x7ffff4422e58 <__mmap+152>) RDX: 0x0 RSI: 0x7ffff46e5b38 --> 0x1694b50 --> 0x0 RDI: 0xffffffff RBP: 0x7fffffffa790 --> 0x7fffffffa800 --> 0x7fffffffa820 --> 0x7fffffffa850 --> 0x7fffffffa880 --> 0x7fffffffa9c0 (--> ...) RSP: 0x7fffffffa6c0 --> 0x7ffff7fbd5b0 --> 0x5a5a5a5a00000001 RIP: 0x618090 (<zif_dom_document_savexml+1082>: mov rax,QWORD PTR [rbp-0x88]) R8 : 0x1694b60 --> 0x0 R9 : 0x60000000 ('') R10: 0x1 R11: 0x207 R12: 0x439790 (<_start>: xor ebp,ebp) R13: 0x7fffffffe1a0 --> 0x2 R14: 0x0 R15: 0x0 EFLAGS: 0x282 (carry parity adjust zero SIGN trap INTERRUPT direction overflow) [-------------------------------------code-------------------------------------] 0x618083 <zif_dom_document_savexml+1069>: mov rax,QWORD PTR [rbp-0x10] 0x618087 <zif_dom_document_savexml+1073>: mov BYTE PTR [rax+0x14],0x3 0x61808b <zif_dom_document_savexml+1077>: jmp 0x618114 <zif_dom_document_savexml+1214> => 0x618090 <zif_dom_document_savexml+1082>: mov rax,QWORD PTR [rbp-0x88] 0x618097 <zif_dom_document_savexml+1089>: mov QWORD PTR [rbp-0x20],rax 0x61809b <zif_dom_document_savexml+1093>: mov eax,DWORD PTR [rbp-0xa8] 0x6180a1 <zif_dom_document_savexml+1099>: mov DWORD PTR [rbp-0x9c],eax 0x6180a7 <zif_dom_document_savexml+1105>: mov rax,QWORD PTR [rbp-0xc0] [------------------------------------stack-------------------------------------] 0000| 0x7fffffffa6c0 --> 0x7ffff7fbd5b0 --> 0x5a5a5a5a00000001 0008| 0x7fffffffa6c8 --> 0x7ffff7f86290 --> 0x7ffff7fc1638 ('Z' <repeats 16 times>, "\001") 0016| 0x7fffffffa6d0 --> 0x7ffff7fc1638 ('Z' <repeats 16 times>, "\001") 0024| 0x7fffffffa6d8 --> 0x1 0032| 0x7fffffffa6e0 --> 0x7ffff7fc15e8 --> 0x7fffae383fab ('a' <repeats 200 times>...) 0040| 0x7fffffffa6e8 --> 0x80000008 0048| 0x7fffffffa6f0 --> 0x7fff00000001 ('a' <repeats 200 times>...) 0056| 0x7fffffffa6f8 --> 0x7ffff7fbd5b0 --> 0x5a5a5a5a00000001 [------------------------------------------------------------------------------] Legend: code, data, rodata, value Breakpoint 1, zif_dom_document_savexml (ht=0x0, return_value=0x7ffff7fc1638, return_value_ptr=0x7ffff7f86290, this_ptr=0x7ffff7fbd5b0, return_value_used=0x1) at /home/user/Desktop/php-5.6.26/ext/dom/document.c:1798 1798 RETVAL_STRINGL(mem, size, 1); gdb-peda$ p size $1 = 0x80000008 <- size is larger than INTMAX gdb-peda$ p mem $2 = (xmlChar *) 0x0 <- mem is NULL gdb-peda$ b zend_alloc.c:2664 Breakpoint 2 at 0xa110da: file /home/user/Desktop/php-5.6.26/Zend/zend_alloc.c, line 2664. gdb-peda$ c Continuing. [----------------------------------registers-----------------------------------] RAX: 0x0 RBX: 0xa93d73 (<execute_ex>: push rbp) RCX: 0x7ffe4d12e010 --> 0x80040000 RDX: 0xe003d8c0 RSI: 0x7ffecd12e080 --> 0x7ffe94d6cac3 --> 0x0 RDI: 0x1425700 --> 0x1 RBP: 0x7fffffffa6b0 --> 0x7fffffffa790 --> 0x7fffffffa800 --> 0x7fffffffa820 --> 0x7fffffffa850 --> 0x7fffffffa880 (--> ...) RSP: 0x7fffffffa670 --> 0x7fffffffa6e8 --> 0x80000008 RIP: 0xa110da (<_estrndup+159>: mov edx,DWORD PTR [rbp-0x1c]) R8 : 0xffffffffffffffff R9 : 0x0 R10: 0x22 ('"') R11: 0x246 R12: 0x439790 (<_start>: xor ebp,ebp) R13: 0x7fffffffe1a0 --> 0x2 R14: 0x0 R15: 0x0 EFLAGS: 0x246 (carry PARITY adjust ZERO sign trap INTERRUPT direction overflow) [-------------------------------------code-------------------------------------] 0xa110d2 <_estrndup+151>: call rax 0xa110d4 <_estrndup+153>: mov rax,QWORD PTR [rbp-0x8] 0xa110d8 <_estrndup+157>: jmp 0xa1111c <_estrndup+225> => 0xa110da <_estrndup+159>: mov edx,DWORD PTR [rbp-0x1c] 0xa110dd <_estrndup+162>: mov rcx,QWORD PTR [rbp-0x18] 0xa110e1 <_estrndup+166>: mov rax,QWORD PTR [rbp-0x8] 0xa110e5 <_estrndup+170>: mov rsi,rcx 0xa110e8 <_estrndup+173>: mov rdi,rax [------------------------------------stack-------------------------------------] 0000| 0x7fffffffa670 --> 0x7fffffffa6e8 --> 0x80000008 0008| 0x7fffffffa678 --> 0x1aacad00 0016| 0x7fffffffa680 --> 0x0 0024| 0x7fffffffa688 --> 0xc14c48 ("/home/user/Desktop/php-5.6.26/ext/dom/document.c") 0032| 0x7fffffffa690 --> 0x8000000800000706 0040| 0x7fffffffa698 --> 0x0 0048| 0x7fffffffa6a0 --> 0x7fffffffe1a0 --> 0x2 0056| 0x7fffffffa6a8 --> 0x7ffe4d12e070 --> 0x0 [------------------------------------------------------------------------------] Legend: code, data, rodata, value Breakpoint 2, _estrndup (s=0x0, length=0x80000008, __zend_filename=0xc14c48 "/home/user/Desktop/php-5.6.26/ext/dom/document.c", __zend_lineno=0x706, __zend_orig_filename=0x0, __zend_orig_lineno=0x0) at /home/user/Desktop/php-5.6.26/Zend/zend_alloc.c:2664 2664 memcpy(p, s, length); gdb-peda$ p length $3 = 0x80000008 <- length is larger than INTMAX gdb-peda$ p s $4 = 0x0 <- source string is NULL gdb-peda$ p p $5 = 0x7ffe4d12e070 "" gdb-peda$ n Program received signal SIGSEGV, Segmentation fault. [----------------------------------registers-----------------------------------] RAX: 0xffff800132ed1f88 RBX: 0xa93d73 (<execute_ex>: push rbp) RCX: 0x100000010 RDX: 0x80000008 RSI: 0x0 RDI: 0x7ffe4d12e070 --> 0x0 RBP: 0x7fffffffa6b0 --> 0x7fffffffa790 --> 0x7fffffffa800 --> 0x7fffffffa820 --> 0x7fffffffa850 --> 0x7fffffffa880 (--> ...) RSP: 0x7fffffffa668 --> 0xa110f0 (<_estrndup+181>: mov edx,DWORD PTR [rbp-0x1c]) RIP: 0x7ffff43c0e10 (<__memcpy_sse2_unaligned+32>: movdqu xmm8,XMMWORD PTR [rsi]) R8 : 0xffffffffffffffff R9 : 0x0 R10: 0x22 ('"') R11: 0x246 R12: 0x439790 (<_start>: xor ebp,ebp) R13: 0x7fffffffe1a0 --> 0x2 R14: 0x0 R15: 0x0 EFLAGS: 0x10202 (carry parity adjust zero sign trap INTERRUPT direction overflow) [-------------------------------------code-------------------------------------] 0x7ffff43c0e00 <__memcpy_sse2_unaligned+16>: jb 0x7ffff43c0f0d <__memcpy_sse2_unaligned+285> 0x7ffff43c0e06 <__memcpy_sse2_unaligned+22>: cmp rdx,0x10 0x7ffff43c0e0a <__memcpy_sse2_unaligned+26>: jbe 0x7ffff43c0f9b <__memcpy_sse2_unaligned+427> => 0x7ffff43c0e10 <__memcpy_sse2_unaligned+32>: movdqu xmm8,XMMWORD PTR [rsi] 0x7ffff43c0e15 <__memcpy_sse2_unaligned+37>: cmp rdx,0x20 0x7ffff43c0e19 <__memcpy_sse2_unaligned+41>: movdqu XMMWORD PTR [rdi],xmm8 0x7ffff43c0e1e <__memcpy_sse2_unaligned+46>: movdqu xmm8,XMMWORD PTR [rsi+rdx*1-0x10] 0x7ffff43c0e25 <__memcpy_sse2_unaligned+53>: movdqu XMMWORD PTR [rdi+rdx*1-0x10],xmm8 [------------------------------------stack-------------------------------------] 0000| 0x7fffffffa668 --> 0xa110f0 (<_estrndup+181>: mov edx,DWORD PTR [rbp-0x1c]) 0008| 0x7fffffffa670 --> 0x7fffffffa6e8 --> 0x80000008 0016| 0x7fffffffa678 --> 0x1aacad00 0024| 0x7fffffffa680 --> 0x0 0032| 0x7fffffffa688 --> 0xc14c48 ("/home/user/Desktop/php-5.6.26/ext/dom/document.c") 0040| 0x7fffffffa690 --> 0x8000000800000706 0048| 0x7fffffffa698 --> 0x0 0056| 0x7fffffffa6a0 --> 0x7fffffffe1a0 --> 0x2 [------------------------------------------------------------------------------] Legend: code, data, rodata, value Stopped reason: SIGSEGV __memcpy_sse2_unaligned () at ../sysdeps/x86_64/multiarch/memcpy-sse2-unaligned.S:35 35 ../sysdeps/x86_64/multiarch/memcpy-sse2-unaligned.S: No such file or directory. gdb-peda$ bt #0 __memcpy_sse2_unaligned () at ../sysdeps/x86_64/multiarch/memcpy-sse2-unaligned.S:35 #1 0x0000000000a110f0 in _estrndup (s=0x0, length=0x80000008, __zend_filename=0xc14c48 "/home/user/Desktop/php-5.6.26/ext/dom/document.c", __zend_lineno=0x706, __zend_orig_filename=0x0, __zend_orig_lineno=0x0) at /home/user/Desktop/php-5.6.26/Zend/zend_alloc.c:2664 #2 0x00000000006180e9 in zif_dom_document_savexml (ht=0x0, return_value=0x7ffff7fc1638, return_value_ptr=0x7ffff7f86290, this_ptr=0x7ffff7fbd5b0, return_value_used=0x1) at /home/user/Desktop/php-5.6.26/ext/dom/document.c:1798 #3 0x0000000000a9476b in zend_do_fcall_common_helper_SPEC ( execute_data=0x7ffff7f866c8) at /home/user/Desktop/php-5.6.26/Zend/zend_vm_execute.h:558 #4 0x0000000000a94f3e in ZEND_DO_FCALL_BY_NAME_SPEC_HANDLER ( execute_data=0x7ffff7f866c8) at /home/user/Desktop/php-5.6.26/Zend/zend_vm_execute.h:693 #5 0x0000000000a93dd3 in execute_ex (execute_data=0x7ffff7f866c8) at /home/user/Desktop/php-5.6.26/Zend/zend_vm_execute.h:363 #6 0x0000000000a93e5a in zend_execute (op_array=0x7ffff7fbe488) at /home/user/Desktop/php-5.6.26/Zend/zend_vm_execute.h:388 #7 0x0000000000a4c498 in zend_execute_scripts (type=0x8, retval=0x0, file_count=0x3) at /home/user/Desktop/php-5.6.26/Zend/zend.c:1341 #8 0x00000000009ad757 in php_execute_script (primary_file=0x7fffffffcd70) at /home/user/Desktop/php-5.6.26/main/main.c:2613 #9 0x0000000000b09556 in do_cli (argc=0x2, argv=0x13f5560) at /home/user/Desktop/php-5.6.26/sapi/cli/php_cli.c:994 #10 0x0000000000b0a8b9 in main (argc=0x2, argv=0x13f5560) at /home/user/Desktop/php-5.6.26/sapi/cli/php_cli.c:1378 #11 0x00007ffff4342830 in __libc_start_main (main=0xb0a09c <main>, argc=0x2, argv=0x7fffffffe1a8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffe198) at ../csu/libc-start.c:291 #12 0x00000000004397b9 in _start ()