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List:       busybox
Subject:    Re: Bugs in cat -n/-b and in bb_process_escape_sequence
From:       Denys Vlasenko <vda.linux () googlemail ! com>
Date:       2018-11-29 12:17:34
Message-ID: CAK1hOcPn2epmqP5OYoTbmU=SgjNOzhGZ1rgE9qoFunUytksp5A () mail ! gmail ! com
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Fixed, thanks!
On Wed, Nov 28, 2018 at 11:13 AM Sébastien Dusuel <seb@dusuel.fr> wrote:
> 
> Hello,
> 
> I found two bugs, tested in busybox 1.27.2 running on ubuntu 18.04. The bugs seem \
> to also be in busybox 1.29.3 (from what could infer by reading from the source). 
> * Bug 1 is a bug in `cat` when run with -n or -b option
> To trigger this bug, simply try to cat a non-existent file, with -n or -b option.
> Although some error message is output, `cat` still tries to process the file, \
> resulting in a segfault (from what I can see in the source, because it uses a FILE \
> *fp which is NULL). For example: $ cat -n A
> cat: A: No such file or directory
> Segmentation fault (core dumped)
> 
> * Bug 2 is a bug that affects many things because it occurs in the function \
> bb_process_escape_sequence defined in libbb/process_escape_sequence.c Examples to \
> trigger it: $ echo -e "\x3@"
> 9
> $ echo -e $(echo -e "\\x\x14\x11")
> A
> 
> I wrote a little program using part of the code of the faulty function to show \
> where the problem occurs (you'll find it in the attachment). It shows that \
> characters \x10 to \x19, \x40, and \x60 are misintepreted as 0 to 9, 9 and 9 \
> (respectively) when they are found in a \x escape sequence. 
> If it can help: decode_dollar_squote defined in shell/ash.c uses \
>                 bb_process_escape_sequence but seems to be unaffected by the bug:
> 00000000: 7368 3a20 0340 3a20 6e6f 7420 666f 756e  sh: .@: not foun
> 00000010: 640a                                     d.
> 
> 
> Best regards,
> Sébastien Dusuel
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> busybox@busybox.net
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