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From: "ssmallkirby at gmail dot com" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sourceware.org Subject: [Bug malloc/27052] New: double free detection mechanism of tcache can invoke endless-loop in _int_free Date: Fri, 11 Dec 2020 13:09:45 +0000 [thread overview] Message-ID: <bug-27052-131@http.sourceware.org/bugzilla/> (raw) https://sourceware.org/bugzilla/show_bug.cgi?id=27052 Bug ID: 27052 Summary: double free detection mechanism of tcache can invoke endless-loop in _int_free Product: glibc Version: 2.32 Status: UNCONFIRMED Severity: minor Priority: P2 Component: malloc Assignee: unassigned at sourceware dot org Reporter: ssmallkirby at gmail dot com Target Milestone: --- Since glibc 2.29, tcache has a 'key' member, which detects double free of tcache chunk. If linked-list of tcache contains a loop, it invokes infinite loop in _int_free. I think this loop should terminate and the program should abort if tcache has more than 7 chunks. Below code invokes such infinite loop in _int_free and the program never terminates. It might be possible for this problem to be abused for DoS attack. // tested on glibc 2.32 #include<stdio.h> #include<stdlib.h> unsigned long protect_ptr(unsigned long pos, unsigned long ptr){ return (pos>>12) ^ (ptr); } int main(void) { char *a,*b,*c; a = malloc(0x50); b = malloc(0x50); c = malloc(0x50); free(a); free(b); *(unsigned long*)(b) = (unsigned long*)protect_ptr(b, b); ((unsigned long*)c)[1] = ((unsigned long*)a)[1]; free(c); return 0; } -- You are receiving this mail because: You are on the CC list for the bug.
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