watch: watch memory changes at specified address.continue: resume program until it breaks again.break: set next stop at instruction after canary store.start: start the program and pause at the beginning of main function.Main (argc=9, argv=0x7fffffffd7f8) at a.c:10ĥ // *** stack smashing detected ***: terminated Temporary breakpoint 1 at 0x401145: file a.c, line 6.
#Linux stack smashing detected error full#
Here is the full session from start to finish to find our corruption: Our task is to get right past store instruction, set canary watch and wait when it gets corrupted. Here the important bit is exact instruction where canary is stored on stack: 0x000000000040114e : mov %rax,-0x8(%rbp) and erased from registers: 0x0000000000401152 : xor %eax,%eax. It's always very close to %fs:0x28 itself. We need to track where it's stored on stack.
Canary is emitted by the compiler if with -enable-default-ssp configure option which enables this option by default.
You don't really need to know much of assembly to find the canary. Canary is a value placed on stack and checked by the compiler to see if anything corrupts canary value. Now the hardest part: we need to find in assembly where canary value was stored and loaded on stack. The interesting part here is the caller of _stack_chk_fail. #3 0x00007fcbdefbd0a2 in _GI_fortify_fail "stack smashing detected") at fortify_fail.c:26 Program terminated with signal SIGABRT, Aborted.
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