https://bugzilla.novell.com/show_bug.cgi?id=891349 https://bugzilla.novell.com/show_bug.cgi?id=891349#c0 Summary: Address zero referenced in libc.so.6, routine free, for arguments that have bits 26-63 unset Classification: openSUSE Product: openSUSE 12.3 Version: Final Platform: x86-64 OS/Version: openSUSE 12.3 Status: NEW Severity: Normal Priority: P5 - None Component: Development AssignedTo: bnc-team-screening@forge.provo.novell.com ReportedBy: shamsundar@uh.edu QAContact: qa-bugs@suse.de Found By: --- Blocker: --- User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.117 Safari/537.36 Problem: If argument to free() has bits 30-63 equal to zero, at offset 7ea24 (see disassembly below) contents of address 0 are referenced,and then a crash is likely. $ /lib64/libc.so.6 GNU C Library (GNU libc) stable release version 2.17 (git c758a6861537), by Roland McGrath et al. Copyright (C) 2012 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Configured for x86_64-suse-linux. Compiled by GNU CC version 4.7.2 20130108 [gcc-4_7-branch revision 195012]. Compiled on a Linux 3.7.1 system. Available extensions: crypt add-on version 2.1 by Michael Glad and others GNU Libidn by Simon Josefsson Native POSIX Threads Library by Ulrich Drepper et al BIND-8.2.3-T5B libc ABIs: UNIQUE IFUNC $ nm /lib64/libc.so.6 | grep -C4 -i ' free$' 00000000000fd590 T __fread_chk 0000000000074f90 T __freading 0000000000075ad0 T fread_unlocked 00000000000fd760 T __fread_unlocked_chk 000000000007e9f0 T free <======= 000000000007e9f0 t __free 00000000000d62a0 T freeaddrinfo 000000000007dd40 t free_atfork 00000000000c2ec0 t free_charset $ objdump -d /lib64/libc.so.6 --start-address=0x7e9f0 --stop-address=0x7eb00 000000000007e9f0 <__libc_free>: 7e9f0: 48 8b 05 c1 94 32 00 mov 0x3294c1(%rip),%rax # 3a7eb8 <_DYNAMIC+0x378> 7e9f7: 48 8b 00 mov (%rax),%rax 7e9fa: 48 85 c0 test %rax,%rax 7e9fd: 75 73 jne 7ea72 <__libc_free+0x82> 7e9ff: 48 85 ff test %rdi,%rdi 7ea02: 74 6c je 7ea70 <__libc_free+0x80> 7ea04: 48 8b 47 f8 mov -0x8(%rdi),%rax 7ea08: 48 8d 77 f0 lea -0x10(%rdi),%rsi 7ea0c: a8 02 test $0x2,%al 7ea0e: 75 20 jne 7ea30 <__libc_free+0x40> 7ea10: a8 04 test $0x4,%al 7ea12: 48 8d 3d 27 9c 32 00 lea 0x329c27(%rip),%rdi # 3a8640 7ea19: 74 0c je 7ea27 <__libc_free+0x37> 7ea1b: 48 89 f0 mov %rsi,%rax 7ea1e: 48 25 00 00 00 fc and $0xfffffffffc000000,%rax 7ea24: 48 8b 38 mov (%rax),%rdi <======= 7ea27: 31 d2 xor %edx,%edx 7ea29: e9 22 cc ff ff jmpq 7b650 <_int_free> Reproducible: Always Steps to Reproduce: 1.The problem was discovered in a complex Fortran program, in a DEALLOCATE statement, which sent the argument to free() as 0x00000000020E5C20. I do not know how to construct a reproducer that generates a valid address with at least one of bits 26 - 63 set. I hope that inspecting the disassembly (see above) will suffice. 2. 3. Actual Results: 1. Inspect disassembly of free() in libc.so.6. 2. Observe instructions that AND the argument to free() to zero out bits 0-25, and then reference the resulting address (at offsets 7EA1E and 7EA24 in the listing above). Expected Results: Code should not try to reference address zero. -- Configure bugmail: https://bugzilla.novell.com/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug.