[bug-diffutils] bug#31935: bug#31935: 2 crashes in diffutills commit version 576645c

[Jim Meyering]

On Fri, Dec 28, 2018 at 5:13 PM Jim Meyering <address@hidden> wrote:
>
> On Fri, Jun 22, 2018 at 7:49 AM Hongxu Chen <address@hidden> wrote:
> >     We found with our fuzzer 2 crashes on diffutils version 576645c: one is 
> > a heap-buffer-overflow at util.c:1249, another is an invalid read resulting 
> > from `output_1_line' at util.c:1274.
> >     The executing command is: `./diff -a --strip-trailing-cr $file 
> > add.wasm` where $file is the poc file (I attached them as  *.input.txt); 
> > "add.wasm" is also attached however it seems that content of the comparison 
> > file is not important.
>
> Thank you for fuzz-testing diffutils.
> FYI, here is a reproducer for the limit[-1]-related UMR bugs:
>
>   valgrind src/diff -a --strip-trailing-cr <(printf '\r') <(echo a)
>
> I've attached a patch:

That patch was provably incomplete.
I ran this (adding -u to the above) and found one new UMR. Guarding
yet another [-1] reference fixes it.
There are still numerous unguarded [-1] references, so this updated
patch is doubtless still incomplete:

for i in hbo*; do echo $i; valgrind --quiet src/diff -u -a
--strip-trailing-cr $i add.wasm > /dev/null; echo $?; done

diffutils-UMR.diff
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