{"id":2470,"date":"2024-08-07T12:32:24","date_gmt":"2024-08-07T04:32:24","guid":{"rendered":"https:\/\/www.yizishun.com\/?p=2470"},"modified":"2024-09-22T14:59:57","modified_gmt":"2024-09-22T06:59:57","slug":"write_malloc","status":"publish","type":"post","link":"https:\/\/www.yizishun.com\/?p=2470","title":{"rendered":"\u91cd\u5199malloc\u548cfree"},"content":{"rendered":"\n<p><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-green-cyan-color\">\u80cc\u666f<\/mark><\/strong>\uff1a\u4f5c\u4e3a\u5373\u5c06\u6b65\u5165\u5927\u4e8c\u7684\u5c0f\u8001\u767b\ud83e\udd13\uff0cCTF\u51fa\u9898\u7684\u538b\u529b\u6765\u5230\u4e86\u6211\u4eec\u7684\u8eab\u4e0a\uff0c\u5728Vidar-Team\u6709\u4e00\u4e2ahgame-mini\u6bd4\u8d5b\uff0c\u7531\u4e8e\u4e00\u4e9b\u6539\u9769\uff0c\u9700\u8981\u5728hgame-mini\u6d89\u53ca\u4e00\u4e9b\u5806\u9898\uff0c\u4f46\u662f\u6709\u4e9b\u4eba\u8ba4\u4e3a\u76f4\u63a5\u4e0a\u5806\u9898\u8fc7\u4e8e\u56f0\u96be\uff0c\u4e8e\u662f\u51b3\u5b9a\u505a\u4e00\u4e9b\u4f2a\u5806\u9898\uff0c\u901a\u8fc7\u91cd\u5199malloc\u548cfree\uff0c\u51cf\u8f7b\u65b0\u751f\u7684\u538b\u529b\uff0c\u867d\u7136\u6211\u6c34\u5e73\u4e0d\u592a\u591f\uff0c\u4f46\u662f\u7ed9\u65b0\u751f\u51fa\u70b9\u9898\u8fd8\u662f\u6ca1\u95ee\u9898\u7684\uff0c\u4e8e\u662f\u6211\u5c31\u51b3\u5b9a\u5199\u4e00\u4efd\u81ea\u5df1\u7684malloc\uff08\u8fd9\u5176\u5b9e\u8fd8\u662f\u6709\u4e9b\u79c1\u5fc3\u7684\uff0c\u91cd\u5199libc\u672c\u6765\u4e5f\u662f\u6211\u5e0c\u671b\u80fd\u5b8c\u6210\u7684\u4e00\u4e2a\u4efb\u52a1\uff09\uff0c\u4ecemalloc\u7684\u8bfb\u8005\u5230malloc\u7684\u8bbe\u8ba1\u8005\uff0c\u611f\u6168\u4e07\u5343<\/p>\n\n\n\n<p>\u8bf4\u5b9e\u5728\u7684\uff0c\u8fd9\u8fd8\u662f\u6211\u7b2c\u4e00\u6b21\u771f\u6b63\u8131\u79bb\u8bb2\u4e49\uff0c\u8131\u79bb\u6846\u67b6\u4ee3\u7801\uff08\u5b9e\u9645\u4e0a\u4e5f\u6709glibc\u7684\u6846\u67b6\u53c2\u8003\uff09\uff0c\u6240\u4ee5\u6211\u9700\u8981\u81ea\u5df1\u6765\u5206\u6b65\uff0c\u5206\u89e3\u4efb\u52a1<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-cyan-blue-color\">\u7f16\u8bd1\u5230\u81ea\u5df1\u7684malloc\u548cfree<\/mark><\/strong><\/h2>\n\n\n\n<p>\u5982\u4f55\u5728\u7a0b\u5e8f\u7f16\u8bd1\u65f6\u4f7f\u7528\u81ea\u5df1\u5199\u7684malloc\uff0c\u8fd9\u662f\u9047\u5230\u7684\u7b2c\u4e00\u4e2a\u95ee\u9898\uff0c\u6211\u4e00\u5f00\u59cb\u60f3\u7684\u662f\u7528LD_PRELOAD\u73af\u5883\u53d8\u91cf\uff0c\u4f46\u662f\u5728\u6211\u7684macos\u4e0a\u59cb\u7ec8\u65e0\u6cd5\u505a\u5230\uff0c\u4e8e\u662f\u91c7\u7528\u5728\u7f16\u8bd1\u65f6\u52a0\u5165\u9009\u9879-fno-builtin\uff0c\u6210\u529f<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-cyan-blue-color\">\u7f16\u5199\u6700\u7b80\u5355\u7684malloc<\/mark><\/strong><\/h2>\n\n\n\n<p>\u9996\u5148\u5fc5\u987b\u4f7fmalloc\u53ef\u4ee5\u8dd1\u8d77\u6765\uff0c\u4e0d\u5b9e\u73b0free\u3002<\/p>\n\n\n\n<p>\u90a3\u5c31\u8981\u786e\u5b9a\u6211\u7684malloc\u7684\u5e95\u5c42\u9700\u8981\u54ea\u4e2asyscall<\/p>\n\n\n\n<p>\u6253\u7b97\u4f7f\u7528sbrk\uff0c\u56e0\u4e3a\u611f\u89c9\u6bd4\u8f83\u7b80\u5355\uff0c\u4f46\u662f<code>warning: 'sbrk' is deprecated<\/code><\/p>\n\n\n\n<p>\u65e0\u6240\u8c13\u4e86<\/p>\n\n\n\n<p>\u529f\u80fd\u63cf\u8ff0\u5982\u4e0b\uff1a\u7b2c\u4e00\u6b21\u8c03\u7528\u65f6mmap\u4e00\u5757\u5de8\u5927\u7684\u5185\u5b58\uff0c\u8fd9\u5757\u5185\u5b58\u4f5c\u4e3a\u4e00\u4e2acache\uff08\u907f\u514d\u4e4b\u540e\u9891\u7e41\u7684\u5411\u64cd\u4f5c\u7cfb\u7edf\u8bf7\u6c42\uff09\uff0c\u8fd9\u5757\u5185\u5b58\u5728ptmalloc2\u4e2d\u79f0\u4e4b\u4e3atopchunk\uff0c\u4e4b\u540e\u7684\u6240\u6709\u5185\u5b58\u8bf7\u6c42\u5747\u4ecetopchunk\u5207\u5272\uff0c\u6240\u6709\u7684free\u5747\u5c1d\u8bd5\u5408\u5e76\u627e\u9644\u8fd1\u7684\u5408\u5e76\uff0c\u6ca1\u6709\u5408\u5e76\u6210\u529f\u7684\u5185\u5b58\u5757\u653e\u5165\u552f\u4e00\uff08\u6682\u65f6\uff09\u7684\u4e00\u4e2abin\uff08unsorted bin\uff09\uff0c\u4e4b\u540e\u7684malloc\u901a\u8fc7\u9996\u5148\u5728unsorted bin\u4e2d\u5bfb\u627e\u82e5\u627e\u5230\u5408\u9002\u5927\u5c0f\u7684\u5219\u5206\u914d\uff0c\u6ca1\u6709\u5408\u9002\u5927\u5c0f\u7684\u5219\u4ecetopchunk\u5207\u5272\uff0cfree\u540c\u7406<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-cyan-blue-color\">\u57fa\u7840\u8bbe\u65bd\u5efa\u8bbe<\/mark><\/strong><\/h3>\n\n\n\n<p>\u57fa\u7840\u8bbe\u65bd\u5305\u62ec\u4e00\u4e9b\u5b8f\u7684\u5b9a\u4e49\uff0ctestbench\u7684\u7f16\u5199\uff0c\u4e00\u4e9bstruct\u7684\u7f16\u5199<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-cyan-blue-color\">sysmalloc<\/mark><\/strong><\/h3>\n\n\n\n<p>\u8fd9\u4e2a\u51fd\u6570\u9700\u8981\u5728\u505a\u5230\u7b2c\u4e00\u6b21malloc\u7684\u65f6\u5019\u63d0\u4f9b\u4e00\u4e2a\u5de8\u5927\u7684topchunk\u4ee5\u53ca\u4e00\u4e2a\u6240\u9700\u5927\u5c0f\u7684chunk\u8fd4\u56de\u7ed9\u7528\u6237\uff0c\u4ee5\u53ca\u5728\u4e4b\u540etopchunk\u7a7a\u95f4\u4e0d\u591f\u65f6\u589e\u5927topchunk\u7684\u5927\u5c0f\u5e76\u63d0\u4f9b\u8fd4\u56de\u4e00\u4e2a\u6240\u9700\u5927\u5c0f\u7684chunk\uff0c\u6682\u65f6\u6ca1\u6709\u7b2c\u4e8c\u4e2a\u7684\u9700\u6c42\uff0c\u6240\u4ee5\u6401\u7f6e\u5148<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-vivid-cyan-blue-color\">malloc\/free<\/mark><\/strong><\/h3>\n\n\n\n<p>malloc\u9996\u5148\u5728unsorted bin\u4e2d\u641c\u7d22\uff0c\u627e\u5230\u4e00\u4e2a\u7533\u8bf7\u7684\u5927\u7684chunk\uff0c\u5982\u679c\u5927\u7684\u5f88\u591a\u5c31\u5207\u5272\uff0c\u5982\u679c\u5927\u7684\u4e0d\u591a\u5c31\u76f4\u63a5\u7ed9\uff0c\u8fd9\u4e2a\u5927\u7684\u591a\u4e0d\u591a\u53d6\u51b3\u4e8e\u5207\u5272\u540e\u6709\u6ca1\u6709\u5927\u4e8eminisize\uff080x20\uff09\uff0c\u8fd9\u79cd\u65b9\u5f0f\u5c31\u662f\u6548\u7387\u7279\u522b\u6162\uff0c\u4f46\u662f\u80af\u5b9a\u80fdwork\uff0c\u5982\u679c\u65e0\u6cd5\u5728unsorted bin\u4e2d\u627e\u5230\u5408\u9002\u7684\uff0c\u5c31\u4ecetopchunk\u5207\u5272<\/p>\n\n\n\n<p>\u5199\u4e4b\u524d\u590d\u4e60\u4e86\u4e00\u4e0b\u8fd9\u4e2abin\u7684\u7ed3\u6784&#8230;..\u54ce\uff0cglibc\uff0c\u4f60\u771f\u7684\u4e0d\u662f\u4eba\u80fd\u770b\u7684<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"741\" height=\"207\" src=\"https:\/\/www.yizishun.com\/wp-content\/uploads\/2024\/08\/image-43.png\" alt=\"\" class=\"wp-image-3185\"\/><\/figure>\n\n\n\n<p>\u5c31\u8fd9\u4e2abin_at\u51e0\u4e4e\u8ba9\u6211\u56f0\u60d1\u4e86\u4e00\u6574\u5929\uff0c\u5c31\u95ee\u8c01\u80fd\u79d2\u770b\u61c2\u8fd9\u4e2a\uff0c\u4ecebins\u4e2d\u53d6\u5730\u5740\uff0c\u518d\u53d6\u8fd9\u4e2a\u5730\u5740\u7684\u5730\u5740\uff0c\u73b0\u5728\u8fd9\u4e2a\u5730\u5740\u5728arena\u4e2d\uff0c\u518d\u5c06\u8fd9\u4e2a\u5730\u5740\u51cf\u4e24\u4e2asize_t\uff0c\u8c01\u80fd\u7406\u89e3\u8fd9\u6837\u505a\u7684\u76ee\u7684\uff1f\uff1f<\/p>\n\n\n\n<p>\u540e\u6765\u5403\u4e2a\u996d\u7ec8\u4e8e\u7406\u89e3\u4e86\uff0c\u5982\u679c\u4f20\u5165i\u4e3a1\uff0c\u786e\u5b9e\u83b7\u5f97\u662fbin[0]-2*size_t\u7684\u5730\u5740\uff0c\u6b64\u65f6\u8fd9\u4e2a\u5730\u5740\u662f\u4ec0\u4e48\u5e76\u4e0d\u91cd\u8981\uff08\u5b9e\u9645\u4e0a\u662farena\u4e2dtop\u6307\u9488\u7684\u5730\u5740\uff09\uff0c\u6700\u4e3b\u8981\u7684\u662f\u901a\u8fc7\u8fd9\u4e2a\u5730\u5740\u6765\u83b7\u5f97\u4ed6\u7684fd\uff0c\u4e5f\u5c31\u662f\u8bf4\u4ed6\u5c06top\u6307\u9488\u7684\u4f4d\u7f6e\u5f53\u6210\u4e86\u4e00\u4e2achunk\uff08\u4f46\u662f\u8fd9\u5e76\u4e0d\u662f\u4e00\u4e2a\u771f\u6b63\u7684chunk\uff09\uff0c\u7136\u540e\u901a\u8fc7-&gt;fd\u7684\u65b9\u5f0f\u6765\u83b7\u5f97\u76f8\u5e94\u7684\u6307\u9488<\/p>\n\n\n\n<p>\u610f\u4e49\u4f55\u5728\uff1f\u76f4\u63a5bins[0]\u4e0d\u4e5f\u53ef\u4ee5\u83b7\u5f97\u5730\u5740\u561b\uff0c\u592a\u8fc7\u8be1\u5f02\uff0c\u4f46\u662f\u4ed6\u4f3c\u4e4e\u8fd4\u56de\u7684\u662f\u4e00\u4e2a\u865a\u62df\u7684chunk<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"1450\" height=\"777\" src=\"https:\/\/www.yizishun.com\/wp-content\/uploads\/2024\/08\/image-44.png\" alt=\"\" class=\"wp-image-3186\"\/><\/figure>\n\n\n\n<p>\u5982\u56fe\u6240\u793a\uff0c\u6700\u91cc\u9762\u7684chunk\u7684fd\u548c\u6700\u5916\u9762\u7684bk\u90fd\u662f\u6307\u5411\u8fd9\u4e2a\u865a\u62dfchunk\u7684\u5934\uff0c\u4ece\u800c\u5176\u5b9e\u5c31\u50cfchunk\u4e4b\u95f4\u5f62\u6210\u4e86\u4e00\u4e2a\u4e0d\u5faa\u73af\u94fe\u8868\uff0c\u4f46\u662f\u52a0\u4e0a\u4e86\u8fd9\u4e2a\u865a\u62dfchunk\u4e4b\u540e\u5c31\u5f62\u6210\u4e86\u4e00\u4e2a\u5faa\u73af\u94fe\u8868\uff0c\u5faa\u73af\u94fe\u8868\u7406\u8bba\u6ca1\u6709\u8d77\u59cb\u70b9\uff0c\u4f46\u662f\u6309\u7167\u4e0d\u5faa\u73af\u94fe\u8868\u7684\u89d2\u5ea6\u6765\u770b\u7684\u8bdd\uff0c\u5faa\u73af\u94fe\u8868\u5176\u5b9e\u8d77\u59cb\u70b9\u662f\u8fd9\u4e2a\u865a\u62dfchunk\uff08\u5373bin_at\u83b7\u5f97\u7684chunk\uff09\uff0c\u865a\u62dfchunk\u7684fd\u6307\u5411\u7b2c\u4e00\u4e2achunk\uff08\u6700\u5916\u9762\u7684chunk\uff09\uff0cbk\u6307\u5411\u6700\u91cc\u9762\u7684chunk<\/p>\n\n\n\n<p>\u5999\u554a\u5999\u554a\uff0c\u54ce\uff0c\u8fd8\u662f\u611f\u89c9\u5f88\u8be1\u5f02\uff08\u4e3b\u8981\u662f\u6ca1\u89c1\u8fc7\u8fd9\u79cd\u64cd\u4f5c\uff09&#8211;\u4ee50\u7a7a\u95f4\u5f00\u9500\u7684\u65b9\u5f0f\u83b7\u5f97\u4e00\u4e2a\u5faa\u73af\u94fe\u8868\u7684\u6027\u80fd\uff0c\u592a\u65e0\u654c\u4e86<\/p>\n\n\n\n<p>\u4e4b\u540e\u5199\u5b8c\u4e4b\u540e\u7684\u6d4b\u8bd5\u662f\u6700\u9ebb\u70e6\u7684\uff0c\u6211\u65e0\u6cd5\u5bf9\u6211\u7684malloc\u9002\u914dpwndbg\uff08\u6216\u8005\u8bf4\u5f88\u96be\uff09\uff0c\u56e0\u4e3apwndbg\u7684\u8c03\u8bd5\u547d\u4ee4\u90fd\u662f\u4ee5glibc malloc\u4f5c\u4e3a\u5b9e\u73b0\u3002\uff08\u4f46\u662f\u6216\u8bb8\u6211\u53ef\u4ee5\u9002\u914d\u4e00\u4e0b\uff0c\u8ba9pwndbg\u80fd\u68c0\u6d4b\u51fa\u6765\uff1f\u6bd5\u7adfpwndbg\u4e5f\u662f\u901a\u8fc7\u4e00\u4e9b\u4e8c\u8fdb\u5236\u6587\u4ef6\u4e2d\u7684\u7b26\u53f7\u6765\u8fdb\u884c\u5806\u63a2\u6d4b\u7684\uff1f\uff09<\/p>\n\n\n\n<p>\u5728\u6d4b\u8bd5malloc\u7684\u65f6\u5019\uff0c\u53d1\u73b0printf\u4f9d\u8d56malloc\uff0c\u5bfc\u81f4\u8c03\u8bd5\u6709\u70b9\u56f0\u96be\uff0c\u6240\u4ee5\u6216\u8bb8\u9700\u8981\u7ed9\u6211\u7684malloc\u548cfree\u6539\u4e00\u4e2a\u540d\u5b57\uff0c\u4f46\u662f\u5176\u5b9e\u6211\u4e0d\u5e0c\u671bprintf\u6539\u53d8\u6211\u7684\u5806\u72b6\u6001<\/p>\n\n\n\n<p>\u4e4b\u540e\u53d1\u73b0\u4f7f\u7528gdb\uff08with gdb script\uff09\u5176\u5b9e\u53ef\u4ee5\u5f88\u8f7b\u677e\u7684\u8fdb\u884c\u6d4b\u8bd5<\/p>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"552\" height=\"426\" src=\"https:\/\/www.yizishun.com\/wp-content\/uploads\/2024\/08\/image-45.png\" alt=\"\" class=\"wp-image-3199\" style=\"width:310px;height:auto\"\/><\/figure>\n\n\n\n<p>\u751a\u81f3\u8fd8\u53ef\u4ee5\u5728gdb\u811a\u672c\u4e2d\u5b9a\u4e49\u51fd\u6570\uff0c\u505a\u66f4\u591a\u7684\u4e8b\u60c5\uff0c\u8fd9\u6837\u5176\u5b9e\u53ef\u4ee5\u83b7\u5f97pwndbg 50%\u7684\u5a01\u80fd\uff0c\u540e\u53d1\u73b0\u5728gdbinit\u4e2d\u53ef\u4ee5\u5bf9pwndbg\u8fdb\u884c\u4e00\u4e9b\u57fa\u672c\u914d\u7f6e\uff0c\u6bd4\u5982\u8ba9\u67d0\u4e9b\u533a\u57df\u4e0d\u663e\u793a\uff08\u6bd4\u5982reg\uff0cstack\u7b49\u533a\u57df\u5bf9\u6211\u5c31\u6ca1\u4ec0\u4e48\u7528\uff09\uff0cpwndbg\u771f\u597d\u263a\ufe0f\u263a\ufe0f<\/p>\n\n\n\n<p>\u5176\u5b9e\u5dee\u4e0d\u591a\u5b8c\u7ed3\u4e86\uff0c\u4e22\u4e00\u4e0b\u4ee3\u7801\u5427<\/p>\n\n\n\n<p><a href=\"https:\/\/github.com\/yizishun\/myLibc\/blob\/master\/src\/malloc.c\">myLibc\/src\/malloc.c at master \u00b7 yizishun\/myLibc (github.com)<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u80cc\u666f\uff1a\u4f5c\u4e3a\u5373\u5c06\u6b65\u5165\u5927\u4e8c\u7684\u5c0f\u8001\u767b\ud83e\udd13\uff0cCTF\u51fa\u9898\u7684\u538b\u529b\u6765\u5230\u4e86\u6211\u4eec&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[48,11],"tags":[49],"class_list":["post-2470","post","type-post","status-publish","format-standard","hentry","category-libc","category-cs","tag-rtfsc"],"_links":{"self":[{"href":"https:\/\/www.yizishun.com\/index.php?rest_route=\/wp\/v2\/posts\/2470","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.yizishun.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.yizishun.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.yizishun.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.yizishun.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2470"}],"version-history":[{"count":29,"href":"https:\/\/www.yizishun.com\/index.php?rest_route=\/wp\/v2\/posts\/2470\/revisions"}],"predecessor-version":[{"id":3202,"href":"https:\/\/www.yizishun.com\/index.php?rest_route=\/wp\/v2\/posts\/2470\/revisions\/3202"}],"wp:attachment":[{"href":"https:\/\/www.yizishun.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2470"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.yizishun.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2470"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.yizishun.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2470"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}