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bash shell parser bug

From: laura fairhead
Subject: bash shell parser bug
Date: Thu, 16 Mar 2006 20:28:28 -0800 (PST)


I just found a bug that affects a number of shells (pressumably the
code there is from the same roots) in the parser.

The following code;

l='eval "$l"'
eval "$l"

Which sets off an infinite recursion on 'eval', should result in an 
infinite loop to be terminated by INT (doesnt' work) or at least
end gracefully with an error "bash: out of memory". Instead the
system has to kill the shell process because of SEGV fault.

I'm not familiar with bash internals but it looks to me like
some sort of heap overflow problem.

I traced the system calls using 'strace' and it is extending the
data area with brk() by 4k a time until finally, pressumaby it
just doesn't check the error from brk() not finding anymroe memory.


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