[binutils-gdb] ld: Avoid overflows in string merging

[binutils-gdb] ld: Avoid overflows in string merging

[Michael Matz]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=836654b1177ab305c36fe7319f08f0ad5d4fac1b

commit 836654b1177ab305c36fe7319f08f0ad5d4fac1b
Author: Michael Matz <matz@suse.de>
Date:   Tue Nov 7 16:54:44 2023 +0100

    ld: Avoid overflows in string merging
    
    as the bug report shows we had an overflow in the test if
    hash table resizing is needed.  Reorder the expression to avoid
    that.  There's still a bug somewhere in gracefully handling
    failure in resizing (e.g. out of memory), but this pushes the
    boundary for that occurring somewhen into the future and
    immediately helps the reporter.
    
        bfd/
    
        PR ld/31009
        * merge.c (NEEDS_RESIZE): New macro avoiding overflow.
        (sec_merge_maybe_resize): Use it.
        (sec_merge_hash_insert): Ditto.

Diff:
---
 bfd/merge.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/bfd/merge.c b/bfd/merge.c
index 722e6659486..61ffab4d706 100644
--- a/bfd/merge.c
+++ b/bfd/merge.c
@@ -94,6 +94,10 @@ struct sec_merge_hash
   struct sec_merge_hash_entry **values;
 };
 
+/* True when given NEWCOUNT and NBUCKETS indicate that the hash table needs
+   resizing.  */
+#define NEEDS_RESIZE(newcount, nbuckets) ((newcount) > (nbuckets) / 3 * 2)
+
 struct sec_merge_sec_info;
 
 /* Information per merged blob.  This is the unit of merging and is
@@ -167,7 +171,7 @@ static bool
 sec_merge_maybe_resize (struct sec_merge_hash *table, unsigned added)
 {
   struct bfd_hash_table *bfdtab = &table->table;
-  if (bfdtab->count + added > table->nbuckets * 2 / 3)
+  if (NEEDS_RESIZE (bfdtab->count + added, table->nbuckets))
     {
       unsigned i;
       unsigned long newnb = table->nbuckets * 2;
@@ -175,7 +179,7 @@ sec_merge_maybe_resize (struct sec_merge_hash *table, unsigned added)
       uint64_t *newl;
       unsigned long alloc;
 
-      while (bfdtab->count + added > newnb * 2 / 3)
+      while (NEEDS_RESIZE (bfdtab->count + added, newnb))
 	{
 	  newnb *= 2;
 	  if (!newnb)
@@ -239,8 +243,8 @@ sec_merge_hash_insert (struct sec_merge_hash *table,
   hashp->alignment = 0;
   hashp->u.suffix = NULL;
   hashp->next = NULL;
-  // We must not need resizing, otherwise _index is wrong
-  BFD_ASSERT (bfdtab->count + 1 <= table->nbuckets * 2 / 3);
+  // We must not need resizing, otherwise the estimation was wrong
+  BFD_ASSERT (!NEEDS_RESIZE (bfdtab->count + 1, table->nbuckets));
   bfdtab->count++;
   table->key_lens[_index] = (hash << 32) | (uint32_t)len;
   table->values[_index] = hashp;