Subject: [PATCH] bugfix/make_hash_table: fix segfault when arg< 0 for make-hash-table

From: Blake Shaw <[email-masked]>
Date: Wed, 18 Jan 2023 14:10:22 +0700

* libguile/hashtab.c (make_hash_table): FIX SEGMENTATION FAULT
Currently on Guix if a user evokes (make-hash-table arg) where
arg < 0, guile segfaults.

This patch adds the most straight forward solution, checking
if the value passed to make-hash-table is less than 0, and if so,
throwing an error with scm_out_of_range to avoid segfaulting.

It builds and passes all tests in a guix shell using the
command:

$ guix shell automake autoconf make flex gnulib gettext libtool \
gperf gmp git libffi -D guile guix -C -- \
./autogen.sh && ./configure && make && make check

afterwards, using: ./meta/guile -q
=> scheme@(guile-user)> (make-hash-table -1)
   ice-9/boot-9.scm:1685:16: In procedure raise-exception:
   Value out of range 0 to< 18446744073709551615: -1

as desired...

I'm not familiar with the inner workings of libguile, but
figured I'd offer a fix regardless, so take this this patch
with a grain of salt, it was a quicky...
---
 libguile/hashtab.c | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/libguile/hashtab.c b/libguile/hashtab.c
index b4f004c1d..9cb5d7a47 100644
--- a/libguile/hashtab.c
+++ b/libguile/hashtab.c
@@ -84,23 +84,24 @@ make_hash_table (unsigned long k, const char *func_name)
   SCM vector;
   scm_t_hashtable *t;
   int i = 0, n = k ? k : 31;
-  while (i + 1 < HASHTABLE_SIZE_N && n > hashtable_size[i])
-    ++i;
-  n = hashtable_size[i];
-
-  vector = scm_c_make_vector (n, SCM_EOL);
-
-  t = scm_gc_malloc_pointerless (sizeof (*t), s_hashtable);
-  t->min_size_index = t->size_index = i;
-  t->n_items = 0;
-  t->lower = 0;
-  t->upper = 9 * n / 10;
+   if (k < i) {
+     scm_out_of_range (func_name, scm_from_ulong (k));
+  } else {
+     while (i + 1 < HASHTABLE_SIZE_N && n > hashtable_size[i])
+       ++i;
+     n = hashtable_size[i];
+     vector = scm_c_make_vector (n, SCM_EOL);
+     t = scm_gc_malloc_pointerless (sizeof (*t), s_hashtable);
+     t->min_size_index = t->size_index = i;
+     t->n_items = 0;
+     t->lower = 0;
+     t->upper = 9 * n / 10;
 
   /* FIXME: we just need two words of storage, not three */
-  return scm_double_cell (scm_tc7_hashtable, SCM_UNPACK (vector),
-                          (scm_t_bits)t, 0);
+     return scm_double_cell (scm_tc7_hashtable, SCM_UNPACK (vector),
+                             (scm_t_bits)t, 0);
+   }
 }
-
 void
 scm_i_rehash (SCM table,
 	      scm_t_hash_fn hash_fn,
-- 
2.38.1