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Work around problem in DWARF decoding library which can result in attempts to read arbitrary bytes as if they were an LEB128 encoded value.

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* dwarf.c (skip_attr_bytes): Accept DWARF versions higher than 4
	when processing the DW_FORM_ref_addr form.
	Skip bytes in DW_FORM_block and DW_FORM_exprloc forms.
	Handle DW_FORM_indirect.
	(get_type_signedness): Allow a limited amount of recursion.
	Do not attempt to decode types that use the DW_FORM_ref_addr form.
	(read_and_display_attr_value): 	Do not attempt to decode types
	that use the DW_FORM_ref_addr form.
This commit is contained in:
Nick Clifton
2020-10-21 17:42:42 +01:00
parent c21f37a889
commit 5962451351
2 changed files with 36 additions and 18 deletions
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11
binutils/ChangeLog
View File

@ -1,3 +1,14 @@
2020-10-21 Nick Clifton <nickc@redhat.com>
* dwarf.c (skip_attr_bytes): Accept DWARF versions higher than 4
when processing the DW_FORM_ref_addr form.
Skip bytes in DW_FORM_block and DW_FORM_exprloc forms.
Handle DW_FORM_indirect.
(get_type_signedness): Allow a limited amount of recursion.
Do not attempt to decode types that use the DW_FORM_ref_addr form.
(read_and_display_attr_value): Do not attempt to decode types
that use the DW_FORM_ref_addr form.
2020-10-20 Alan Modra <amodra@gmail.com>
* readelf.c: Delete whitespace at end of line throughout.

39
binutils/dwarf.c
View File

@ -1868,7 +1868,7 @@ skip_attr_bytes (unsigned long form,
case DW_FORM_ref_addr:
if (dwarf_version == 2)
SAFE_BYTE_GET_AND_INC (uvalue, data, pointer_size, end);
else if (dwarf_version == 3 || dwarf_version == 4)
else if (dwarf_version > 2)
SAFE_BYTE_GET_AND_INC (uvalue, data, offset_size, end);
else
return NULL;
@ -1920,6 +1920,7 @@ skip_attr_bytes (unsigned long form,
case DW_FORM_ref8:
case DW_FORM_data8:
case DW_FORM_ref_sig8:
data += 8;
break;
@ -1934,6 +1935,7 @@ skip_attr_bytes (unsigned long form,
case DW_FORM_block:
case DW_FORM_exprloc:
READ_ULEB (uvalue, data, end);
data += uvalue;
break;
case DW_FORM_block1:
@ -1951,12 +1953,12 @@ skip_attr_bytes (unsigned long form,
data += 4 + uvalue;
break;
case DW_FORM_ref_sig8:
data += 8;
break;
case DW_FORM_indirect:
/* FIXME: Handle this form. */
READ_ULEB (form, data, end);
if (form == DW_FORM_implicit_const)
SKIP_ULEB (data, end);
return skip_attr_bytes (form, data, end, pointer_size, offset_size, dwarf_version, value_return);
default:
return NULL;
}
@ -1978,7 +1980,7 @@ get_type_signedness (unsigned char * start,
dwarf_vma offset_size,
int dwarf_version,
bfd_boolean * is_signed,
bfd_boolean is_nested)
unsigned int nesting)
{
unsigned long abbrev_number;
abbrev_entry * entry;
@ -1997,6 +1999,14 @@ get_type_signedness (unsigned char * start,
/* FIXME: Issue a warning ? */
return;
#define MAX_NESTING 20
if (nesting > MAX_NESTING)
{
/* FIXME: Warn - or is this expected ?
NB/ We need to avoid infinite recursion. */
return;
}
for (attr = entry->first_attr;
attr != NULL && attr->attribute;
attr = attr->next)
@ -2019,16 +2029,12 @@ get_type_signedness (unsigned char * start,
#endif
case DW_AT_type:
/* Recurse. */
if (is_nested)
{
/* FIXME: Warn - or is this expected ?
NB/ We need to avoid infinite recursion. */
return;
}
if (uvalue >= (size_t) (end - start))
return;
/* We cannot correctly process DW_FORM_ref_addr at the moment. */
if (attr->form != DW_FORM_ref_addr)
get_type_signedness (start, start + uvalue, end, pointer_size,
offset_size, dwarf_version, is_signed, TRUE);
offset_size, dwarf_version, is_signed, nesting + 1);
break;
case DW_AT_encoding:
@ -2206,7 +2212,6 @@ read_and_display_attr_value (unsigned long attribute,
SAFE_BYTE_GET_AND_INC (uvalue, data, offset_size, end);
else
error (_("Internal error: DW_FORM_ref_addr is not supported in DWARF version 1.\n"));
break;
case DW_FORM_addr:
@ -2663,8 +2668,10 @@ read_and_display_attr_value (unsigned long attribute,
{
bfd_boolean is_signed = FALSE;
/* We cannot correctly process DW_FORM_ref_addr at the moment. */
if (form != DW_FORM_ref_addr)
get_type_signedness (start, start + uvalue, end, pointer_size,
offset_size, dwarf_version, & is_signed, FALSE);
offset_size, dwarf_version, & is_signed, 0);
level_type_signed[level] = is_signed;
}
break;