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Fix vi mode crashes when going back one word (#246)

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This bug was originally reported at <https://github.com/att/ast/issues/1467>.
A crash can occur when using the 'b' or 'B' vi mode commands to go back
one word. I was able to reproduce these crashes with 100% consistency on
an OpenBSD virtual machine when ksh is compiled with -D_std_malloc.
Reproducer:
    $ set -o vi
    $ asdf <ESC> <b or B>

The fix is based on Matthew DeVore's analysis:
> I suspect this is caused by this line:
>> while (vi_isalph(tcur_virt) && tcur_virt >= first_virt) --tcur_virt;
> which is in the b codepath. It checks vi_isalph(tcur_virt) before checking
> if tcur_virt is in range. These two clauses should be reversed. Note that
> line 316 is a similar check for pressing B, and there the tcur_virt value
> is checked first.

src/cmd/ksh93/edit/vi.c:
- Check tcur_virt before using isalph() or isblank() to fix both crashes.
  At the start of the backword() while loop this check was performed
  twice, so the redundant check has been removed.

src/cmd/ksh93/tests/pty.sh:
- Add a regression test for the b, B, w and W editor commands.
This commit is contained in:
Johnothan King 2021-03-30 03:25:20 -07:00 • committed by GitHub
parent f8de1f111d
commit 113a9392ff
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
4 changed files with 34 additions and 20 deletions
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34
src/cmd/ksh93/edit/vi.c
View file

@ -664,8 +664,7 @@ static void backword(Vi_t *vp,int nwords, register int cmd)
register int tcur_virt = cur_virt;
while( nwords-- && tcur_virt > first_virt )
{
if( !isblank(tcur_virt) && isblank(tcur_virt-1)
&& tcur_virt>first_virt )
if( !isblank(tcur_virt) && isblank(tcur_virt-1) )
--tcur_virt;
else if(cmd != 'B')
{
@ -674,21 +673,20 @@ static void backword(Vi_t *vp,int nwords, register int cmd)
if((!cur && last) || (cur && !last))
--tcur_virt;
}
while( isblank(tcur_virt) && tcur_virt>=first_virt )
while( tcur_virt >= first_virt && isblank(tcur_virt) )
--tcur_virt;
if( cmd == 'B' )
{
while( !isblank(tcur_virt) && tcur_virt>=first_virt )
while( tcur_virt >= first_virt && !isblank(tcur_virt) )
--tcur_virt;
}
else
{
if(isalph(tcur_virt))
while( isalph(tcur_virt) && tcur_virt>=first_virt )
while( tcur_virt >= first_virt && isalph(tcur_virt) )
--tcur_virt;
else
while( !isalph(tcur_virt) && !isblank(tcur_virt)
&& tcur_virt>=first_virt )
while( tcur_virt >= first_virt && !isalph(tcur_virt) && !isblank(tcur_virt) )
--tcur_virt;
}
cur_virt = ++tcur_virt;
@ -1235,23 +1233,22 @@ static void endword(Vi_t *vp, int nwords, register int cmd)
register int tcur_virt = cur_virt;
while( nwords-- )
{
if( !isblank(tcur_virt) && tcur_virt<=last_virt )
if( tcur_virt <= last_virt && !isblank(tcur_virt) )
++tcur_virt;
while( isblank(tcur_virt) && tcur_virt<=last_virt )
while( tcur_virt <= last_virt && isblank(tcur_virt) )
++tcur_virt;
if( cmd == 'E' )
{
while( !isblank(tcur_virt) && tcur_virt<=last_virt )
while( tcur_virt <= last_virt && !isblank(tcur_virt) )
++tcur_virt;
}
else
{
if( isalph(tcur_virt) )
while( isalph(tcur_virt) && tcur_virt<=last_virt )
while( tcur_virt <= last_virt && isalph(tcur_virt) )
++tcur_virt;
else
while( !isalph(tcur_virt) && !isblank(tcur_virt)
&& tcur_virt<=last_virt )
while( tcur_virt <= last_virt && !isalph(tcur_virt) && !isblank(tcur_virt) )
++tcur_virt;
}
if( tcur_virt > first_virt )
@ -1274,24 +1271,23 @@ static void forward(Vi_t *vp,register int nwords, int cmd)
{
if( cmd == 'W' )
{
while( !isblank(tcur_virt) && tcur_virt < last_virt )
while( tcur_virt < last_virt && !isblank(tcur_virt) )
++tcur_virt;
}
else
{
if( isalph(tcur_virt) )
{
while( isalph(tcur_virt) && tcur_virt<last_virt )
while( tcur_virt < last_virt && isalph(tcur_virt) )
++tcur_virt;
}
else
{
while( !isalph(tcur_virt) && !isblank(tcur_virt)
&& tcur_virt < last_virt )
while( tcur_virt < last_virt && !isalph(tcur_virt) && !isblank(tcur_virt) )
++tcur_virt;
}
}
while( isblank(tcur_virt) && tcur_virt < last_virt )
while( tcur_virt < last_virt && isblank(tcur_virt) )
++tcur_virt;
}
cur_virt = tcur_virt;
@ -1606,7 +1602,7 @@ static int mvcursor(register Vi_t* vp,register int motion)
case '^': /** First nonblank character **/
tcur_virt = first_virt;
while( isblank(tcur_virt) && tcur_virt < last_virt )
while( tcur_virt < last_virt && isblank(tcur_virt) )
++tcur_virt;
break;