Dear diary, on Thu, Apr 14, 2005 at 02:53:54PM CEST, I got a letter
where Ingo Molnar <[EMAIL PROTECTED]> told me that...
> this patch fixes a 1-byte overflow in show-files.c (looks narrow is is
> probably not exploitable). A specially crafted db object (tree) might
> trigger this overflow.
> 'fullname' is an array of 4096+1 bytes, and we do readdir(), which
> produces entries that have strings with a length of 0-255 bytes. With a
> long enough 'base', it's possible to construct a tree with a name in it
> that has directory whose name ends precisely at offset 4095. At that
> point this code:
> case DT_DIR:
> memcpy(fullname + baselen + len, "/", 2);
> will attempt to append a "/" string to the directory name - resulting in
> a 1-byte overflow (a zero byte is written to offset 4097, which is
> outside the array).
The name ends precisely at offset 4095 with its NUL character:
Maximum number of bytes in a pathname, including the terminating
[ http://www.opengroup.org/onlinepubs/009695399/basedefs/limits.h.html ]
So, if I'm not mistaken, '/' will be written at offset 4095 instead of
the NUL and the NUL will be written at 4096. Everything's fine, right?
Petr "Pasky" Baudis
C++: an octopus made by nailing extra legs onto a dog. -- Steve Taylor
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