Hi Dominique!
On Di, 14 Feb 2017, Dominique Pellé wrote:
> Hi
>
> afl-fuzz found another command that causes access to
> invalid memory in Vim-8.0.329. It's not a recent regression
> since bug is present in at least Vim-7.4.52 that comes
> with ubuntu-14.04.
>
> I have not been able to find a fix yet.
>
> Step to reproduce:
>
> $ valgrind vim -u NONE -c'norm oxx' -c'norm vapo' -c'q!' 2>vg.log
>
> And vg.log contains:
>
> ==4259== Memcheck, a memory error detector
> ==4259== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
> ==4259== Using Valgrind-3.12.0.SVN and LibVEX; rerun with -h for copyright
> info
> ==4259== Command: vim -u NONE -cnorm\ oxx -cnorm\ vapo -cq!
> ==4259==
> ==4259== Invalid read of size 1
> ==4259== at 0x4CF4A0: utf_head_off (mbyte.c:3746)
> ==4259== by 0x4D094C: mb_adjustpos (mbyte.c:4028)
> ==4259== by 0x4E11C9: normal_cmd (normal.c:1292)
> ==4259== by 0x468F25: exec_normal (ex_docmd.c:10418)
> ==4259== by 0x469076: ex_normal (ex_docmd.c:10310)
> ==4259== by 0x46B734: do_one_cmd (ex_docmd.c:2981)
> ==4259== by 0x46B734: do_cmdline (ex_docmd.c:1120)
> ==4259== by 0x5BFC2B: exe_commands (main.c:2905)
> ==4259== by 0x5BFC2B: vim_main2 (main.c:781)
> ==4259== by 0x40C3D3: main (main.c:415)
> ==4259== Address 0xa95bc50 is 0 bytes after a block of size 4,096 alloc'd
> ==4259== at 0x4C2ABF5: malloc (vg_replace_malloc.c:299)
> ==4259== by 0x4C4D0B: lalloc (misc2.c:942)
> ==4259== by 0x5C0830: mf_alloc_bhdr.isra.3 (memfile.c:907)
> ==4259== by 0x5C1546: mf_new (memfile.c:381)
> ==4259== by 0x4AC6FF: ml_new_data (memline.c:3513)
> ==4259== by 0x4AF0FC: ml_open (memline.c:400)
> ==4259== by 0x414DD6: open_buffer (buffer.c:163)
> ==4259== by 0x5BF891: create_windows (main.c:2677)
> ==4259== by 0x5BF891: vim_main2 (main.c:704)
> ==4259== by 0x40C3D3: main (main.c:415)
>
> Possibly related to this, the following command does not
> seem to behave correctly, even if it does not trigger invalid
> memory:
>
> $ echo "foo bar" | vim -u NONE -c'norm wvapo' -
>
> Then press o multiple times and observe that cursor
> alternates between the beginning of the visual block
> and the *middle* of the visual block. I would expect it to
> alternate between the beginning and the *end* of the
> visual block.
Interesting. The second issue happens, because current_par does
internally switch to visual line mode, but does not reset the VIsual
column correctly. This patch fixes it:
diff --git a/src/search.c b/src/search.c
index 36410e50f..ffda65837 100644
--- a/src/search.c
+++ b/src/search.c
@@ -4241,6 +4241,7 @@ extend:
* line, we get stuck there. Trap this here. */
if (VIsual_mode == 'V' && start_lnum == curwin->w_cursor.lnum)
goto extend;
+ VIsual.col = 0;
VIsual.lnum = start_lnum;
VIsual_mode = 'V';
redraw_curbuf_later(INVERTED); /* update the inversion */
As a side effect this also disables switching cursor position using 'o'
which is currently a no-op when only a single line is selected (since it
effectively switches positions between the start of line and the start
of line).
Interestingly, I never noticed that this does nothing currently if a
single visual line is selected.
As it stands, I think this also fixes the invalid read mentioned above.
I just wanted to take a look at that issue, when I noticed that this
patch does not exhibit this behaviour, so I didn't check very closely
why it works.
I tried to add a test, to verify that this is fixed, but whatever I do,
I always get back col 0 for the visual mode. I think this is because in
getmark_buf_fnum() (mark.c:417) the column is explicitly set to zero for
visual line mode and also using getpos('v') does not work, since by the
time I run it, Visual mode is no longer active, so I cannot verify that
this works in vimscript.
Best,
Christian
--
Mein Freund, ich brauche dich - wie eine Höhe, in der man anders
atmet.
-- Antoine de Saint-Exupéry
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