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[PATCH] libdw: Don't overflow stack with user defined macro attributes array.
- From: Mark Wielaard <mjw at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Tue, 21 Apr 2015 15:54:51 +0200
- Subject: [PATCH] libdw: Don't overflow stack with user defined macro attributes array.
In theory user defined debug macros can have an arbitrary number of
arguments. Don't allocate them all on stack. If there are more than
8 (arbitrary number, but no sane macro should have more arguments),
then dynamically allocate and free the attributes.
Found by gcc -fsanitize=undefined. Which pointed out the nforms could
be zero, creating an empty vla (which could cause undefined behavior).
Signed-off-by: Mark Wielaard <mjw@redhat.com>
---
libdw/ChangeLog | 5 +++++
libdw/dwarf_getmacros.c | 23 +++++++++++++++++++++--
2 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 3abb382..87c7d82 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,8 @@
+2015-04-21 Mark Wielaard <mjw@redhat.com>
+
+ * dwarf_getmacros.c (read_macros): Allocate attributes dynamically
+ when there are more than 8.
+
2015-04-01 Petr Machata <pmachata@redhat.com>
* libdwP.h (DWARF_E_NOT_CUDIE): New enumerator.
diff --git a/libdw/dwarf_getmacros.c b/libdw/dwarf_getmacros.c
index f9f2996..c5d47d6 100644
--- a/libdw/dwarf_getmacros.c
+++ b/libdw/dwarf_getmacros.c
@@ -361,7 +361,22 @@ read_macros (Dwarf *dbg, int sec_index,
.endp = (void *) endp,
};
- Dwarf_Attribute attributes[proto->nforms];
+ Dwarf_Attribute *attributes;
+ Dwarf_Attribute *attributesp = NULL;
+ Dwarf_Attribute nattributes[8];
+ if (unlikely (proto->nforms > 8))
+ {
+ attributesp = malloc (sizeof (Dwarf_Attribute) * proto->nforms);
+ if (attributesp == NULL)
+ {
+ __libdw_seterrno (DWARF_E_NOMEM);
+ return -1;
+ }
+ attributes = attributesp;
+ }
+ else
+ attributes = &nattributes[0];
+
for (Dwarf_Word i = 0; i < proto->nforms; ++i)
{
/* We pretend this is a DW_AT_GNU_macros attribute so that
@@ -385,7 +400,11 @@ read_macros (Dwarf *dbg, int sec_index,
.attributes = attributes,
};
- if (callback (¯o, arg) != DWARF_CB_OK)
+ int res = callback (¯o, arg);
+ if (unlikely (attributesp != NULL))
+ free (attributesp);
+
+ if (res != DWARF_CB_OK)
return readp - startp;
}
--
2.1.0