From: Mark Wielaard Date: Tue, 21 Apr 2015 13:46:01 +0000 (+0200) Subject: libdw: Don't overflow stack with user defined macro attributes array. X-Git-Tag: elfutils-0.162~89 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f98b99db09f80666d5cf491a2ce126a59af0fdb1;p=thirdparty%2Felfutils.git 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 --- diff --git a/libdw/ChangeLog b/libdw/ChangeLog index 3abb38283..87c7d821f 100644 --- a/libdw/ChangeLog +++ b/libdw/ChangeLog @@ -1,3 +1,8 @@ +2015-04-21 Mark Wielaard + + * dwarf_getmacros.c (read_macros): Allocate attributes dynamically + when there are more than 8. + 2015-04-01 Petr Machata * libdwP.h (DWARF_E_NOT_CUDIE): New enumerator. diff --git a/libdw/dwarf_getmacros.c b/libdw/dwarf_getmacros.c index f9f29961f..740368ef0 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 @@ -373,8 +388,11 @@ read_macros (Dwarf *dbg, int sec_index, attributes[i].cu = &fake_cu; size_t len = __libdw_form_val_len (&fake_cu, proto->forms[i], readp); - if (len == (size_t) -1) - return -1; + if (unlikely (len == (size_t) -1)) + { + free (attributesp); + return -1; + } readp += len; } @@ -385,7 +403,11 @@ 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; }