On Mon, Jan 24, 2022 at 12:59 PM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@xxxxxxx> wrote:
-----Original Message-----
> > diff --git a/gdb-10.2.patch b/gdb-10.2.patch
> > index 1332b6638028..16165839b360 100644
> > --- a/gdb-10.2.patch
> > +++ b/gdb-10.2.patch
> > @@ -1591,3 +1591,32 @@
> > max += 2;
> > limit = cols / max;
> > if (limit != 1 && (limit * max == cols))
> > +--- gdb-10.2/gdb/ada-lang.c.orig
> > ++++ gdb-10.2/gdb/ada-lang.c
> > +@@ -997,7 +997,7 @@ ada_fold_name (gdb::string_view name)
> > + int len = name.size ();
> > + GROW_VECT (fold_buffer, fold_buffer_size, len + 1);
> > +
> > +- if (name[0] == '\'')
> > ++ if (name.size () > 0 && name[0] == '\'')
> > + {
> > + strncpy (fold_buffer, name.data () + 1, len - 2);
> > + fold_buffer[len - 2] = '\000';
> > +@@ -1006,7 +1006,7 @@ ada_fold_name (gdb::string_view name)
> > + {
> > + int i;
> > +
> > +- for (i = 0; i <= len; i += 1)
> > ++ for (i = 0; i < len; i++)
> > + fold_buffer[i] = tolower (name[i]);
>
> According to 2ccee230f830 ("Fix off-by-one error in ada_fold_name"),
> please add this:
>
> + fold_buffer[i] = '\0';
>
>
>
> No, the above change will definitely cause a core dump because it assigns the value '\0' to a null pointer
> when the name string is null.
Hmm, I'm not familiar with gdb source, could you explain a little more?
The following is the function with your patch.
static char *
ada_fold_name (gdb::string_view name)
{
static char *fold_buffer = NULL;
static size_t fold_buffer_size = 0;
int len = name.size ();
GROW_VECT (fold_buffer, fold_buffer_size, len + 1);
if (name.size () > 0 && name[0] == '\'')
{
strncpy (fold_buffer, name.data () + 1, len - 2);
fold_buffer[len - 2] = '\000';
}
else
{
int i;
for (i = 0; i < len; i++)
fold_buffer[i] = tolower (name[i]);
}
return fold_buffer;
}
The GROW_VECT() looks to alloc 1 byte to fold_buffer if name.size() is zero.
Theoretically yes, but you could notice that the definition of 'fold_buffer_size', actually it is a static variable, the ada_fold_name() may be called many times, but variable 'fold_buffer_size' is only initialized to zero once, it means that the value of 'fold_buffer_size' may not be zero(>1) in the subsequent calls. For this case, the GROW_VECT() will never allocate new memory.
See the definition of GROW_VECT():
#define GROW_VECT(v, s, m) \
if ((s) < (m)) (v) = (char *) grow_vect (v, &(s), m, sizeof *(v));
/* Assuming VECT points to an array of *SIZE objects of size
ELEMENT_SIZE, grow it to contain at least MIN_SIZE objects,
updating *SIZE as necessary and returning the (new) array. */
static void *
grow_vect (void *vect, size_t *size, size_t min_size, int element_size)
{
if (*size < min_size)
{
*size *= 2;
if (*size < min_size)
*size = min_size;
vect = xrealloc (vect, *size * element_size);
}
return vect;
}
if ((s) < (m)) (v) = (char *) grow_vect (v, &(s), m, sizeof *(v));
/* Assuming VECT points to an array of *SIZE objects of size
ELEMENT_SIZE, grow it to contain at least MIN_SIZE objects,
updating *SIZE as necessary and returning the (new) array. */
static void *
grow_vect (void *vect, size_t *size, size_t min_size, int element_size)
{
if (*size < min_size)
{
*size *= 2;
if (*size < min_size)
*size = min_size;
vect = xrealloc (vect, *size * element_size);
}
return vect;
}
Hope this helps.
Thanks
Lianbo
Then len is zero, and nothing is done in the for loop, and fold_buffer[i]
(== fold_buffer[0]) can be set '\0', I thought.
> + fold_buffer[i] = '\0';
And as far as I've tried, no abort occured.
Thanks,
Kazu
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