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systemtap/SystemTap-1.0-unwind-table-size-checks.patch
Josh Stone 0683af9b3b Fixes for CVE-2009-2911
2009-10-21 15:36:43 +00:00

181 lines
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diff --git a/runtime/unwind.c b/runtime/unwind.c
index 00108a3..7607770 100644
--- a/runtime/unwind.c
+++ b/runtime/unwind.c
@@ -88,7 +88,7 @@ static sleb128_t get_sleb128(const u8 **pcur, const u8 *end)
/* given an FDE, find its CIE */
static const u32 *cie_for_fde(const u32 *fde, void *unwind_data,
- int is_ehframe)
+ uint32_t table_len, int is_ehframe)
{
const u32 *cie;
@@ -118,6 +118,11 @@ static const u32 *cie_for_fde(const u32 *fde, void *unwind_data,
else
cie = unwind_data + fde[1];
+ /* Make sure address falls in the table */
+ if (((void *)cie) < ((void*)unwind_data)
+ || ((void*)cie) > ((void*)(unwind_data + table_len)))
+ return NULL;
+
if (*cie <= sizeof(*cie) + 4 || *cie >= fde[1] - sizeof(*fde)
|| (*cie & (sizeof(*cie) - 1))
|| (cie[1] != 0xffffffff && cie[1] != 0)) {
@@ -200,7 +205,8 @@ static unsigned long read_pointer(const u8 **pLoc, const void *end, signed ptrTy
return value;
}
-static signed fde_pointer_type(const u32 *cie)
+static signed fde_pointer_type(const u32 *cie, void *unwind_data,
+ uint32_t table_len)
{
const u8 *ptr = (const u8 *)(cie + 2);
unsigned version = *ptr;
@@ -212,11 +218,16 @@ static signed fde_pointer_type(const u32 *cie)
const u8 *end = (const u8 *)(cie + 1) + *cie;
uleb128_t len;
+ /* end of cie should fall within unwind table. */
+ if (((void*)end) < ((void *)unwind_data)
+ || ((void *)end) > ((void *)(unwind_data + table_len)))
+ return -1;
+
/* check if augmentation size is first (and thus present) */
if (*ptr != 'z')
return -1;
/* check if augmentation string is nul-terminated */
- if ((ptr = memchr(aug = (const void *)ptr, 0, end - ptr)) == NULL)
+ if ((ptr = memchr(aug = (const void *)ptr, 0, end - ptr)) == NULL)
return -1;
++ptr; /* skip terminator */
get_uleb128(&ptr, end); /* skip code alignment */
@@ -267,6 +278,10 @@ static void set_rule(uleb128_t reg, enum item_location where, uleb128_t value, s
}
}
+/* Limit the number of instructions we process. Arbitrary limit.
+ 512 should be enough for anybody... */
+#define MAX_CFI 512
+
static int processCFI(const u8 *start, const u8 *end, unsigned long targetLoc, signed ptrType, struct unwind_state *state)
{
union {
@@ -276,6 +291,9 @@ static int processCFI(const u8 *start, const u8 *end, unsigned long targetLoc, s
} ptr;
int result = 1;
+ if (end - start > MAX_CFI)
+ return 0;
+
dbug_unwind(1, "targetLoc=%lx state->loc=%lx\n", targetLoc, state->loc);
if (start != state->cieStart) {
state->loc = state->org;
@@ -606,10 +624,10 @@ static int unwind_frame(struct unwind_frame_info *frame,
/* found the fde, now set startLoc and endLoc */
if (fde != NULL) {
- cie = cie_for_fde(fde, table, is_ehframe);
+ cie = cie_for_fde(fde, table, table_len, is_ehframe);
if (likely(cie != NULL && cie != &bad_cie && cie != &not_fde)) {
ptr = (const u8 *)(fde + 2);
- ptrType = fde_pointer_type(cie);
+ ptrType = fde_pointer_type(cie, table, table_len);
startLoc = read_pointer(&ptr, (const u8 *)(fde + 1) + *fde, ptrType);
startLoc = adjustStartLoc(startLoc, m, s, ptrType, is_ehframe);
@@ -632,12 +650,12 @@ static int unwind_frame(struct unwind_frame_info *frame,
for (fde = table, tableSize = table_len; cie = NULL, tableSize > sizeof(*fde)
&& tableSize - sizeof(*fde) >= *fde; tableSize -= sizeof(*fde) + *fde, fde += 1 + *fde / sizeof(*fde)) {
dbug_unwind(3, "fde=%lx tableSize=%d\n", (long)*fde, (int)tableSize);
- cie = cie_for_fde(fde, table, is_ehframe);
+ cie = cie_for_fde(fde, table, table_len, is_ehframe);
if (cie == &bad_cie) {
cie = NULL;
break;
}
- if (cie == NULL || cie == &not_fde || (ptrType = fde_pointer_type(cie)) < 0)
+ if (cie == NULL || cie == &not_fde || (ptrType = fde_pointer_type(cie, table, table_len)) < 0)
continue;
ptr = (const u8 *)(fde + 2);
@@ -666,6 +684,12 @@ static int unwind_frame(struct unwind_frame_info *frame,
state.cieEnd = ptr; /* keep here temporarily */
ptr = (const u8 *)(cie + 2);
end = (const u8 *)(cie + 1) + *cie;
+
+ /* end should fall within unwind table. */
+ if (((void *)end) < table
+ || ((void *)end) > ((void *)(table + table_len)))
+ goto err;
+
frame->call_frame = 1;
if ((state.version = *ptr) != 1) {
dbug_unwind(1, "CIE version number is %d. 1 is supported.\n", state.version);
@@ -723,6 +747,11 @@ static int unwind_frame(struct unwind_frame_info *frame,
state.cieEnd = end;
end = (const u8 *)(fde + 1) + *fde;
+ /* end should fall within unwind table. */
+ if (((void*)end) < table
+ || ((void *)end) > ((void *)(table + table_len)))
+ goto err;
+
/* skip augmentation */
if (((const char *)(cie + 2))[1] == 'z') {
uleb128_t augSize = get_uleb128(&ptr, end);
diff --git a/runtime/unwind/unwind.h b/runtime/unwind/unwind.h
index 285a3a3..023ea60 100644
--- a/runtime/unwind/unwind.h
+++ b/runtime/unwind/unwind.h
@@ -143,8 +143,10 @@ static unsigned long read_pointer(const u8 **pLoc,
const void *end,
signed ptrType);
static const u32 bad_cie, not_fde;
-static const u32 *cie_for_fde(const u32 *fde, void *table, int is_ehframe);
-static signed fde_pointer_type(const u32 *cie);
+static const u32 *cie_for_fde(const u32 *fde, void *table,
+ uint32_t table_len, int is_ehframe);
+static signed fde_pointer_type(const u32 *cie,
+ void *table, uint32_t table_len);
#endif /* STP_USE_DWARF_UNWINDER */
diff --git a/translate.cxx b/translate.cxx
index bc5d615..9d456bc 100644
--- a/translate.cxx
+++ b/translate.cxx
@@ -29,6 +29,11 @@ extern "C" {
#include <elfutils/libdwfl.h>
}
+// Max unwind table size (debug or eh) per module. Somewhat arbitrary
+// limit (a bit more than twice the .debug_frame size of my local
+// vmlinux for 2.6.31.4-83.fc12.x86_64)
+#define MAX_UNWIND_TABLE_SIZE (3 * 1024 * 1024)
+
using namespace std;
struct var;
@@ -4785,6 +4790,9 @@ dump_unwindsyms (Dwfl_Module *m,
get_unwind_data (m, &debug_frame, &eh_frame, &debug_len, &eh_len, &eh_addr);
if (debug_frame != NULL && debug_len > 0)
{
+ if (debug_len > MAX_UNWIND_TABLE_SIZE)
+ throw semantic_error ("module debug unwind table size too big");
+
c->output << "#if defined(STP_USE_DWARF_UNWINDER) && defined(STP_NEED_UNWIND_DATA)\n";
c->output << "static uint8_t _stp_module_" << stpmod_idx
<< "_debug_frame[] = \n";
@@ -4802,6 +4810,9 @@ dump_unwindsyms (Dwfl_Module *m,
if (eh_frame != NULL && eh_len > 0)
{
+ if (eh_len > MAX_UNWIND_TABLE_SIZE)
+ throw semantic_error ("module eh unwind table size too big");
+
c->output << "#if defined(STP_USE_DWARF_UNWINDER) && defined(STP_NEED_UNWIND_DATA)\n";
c->output << "static uint8_t _stp_module_" << stpmod_idx
<< "_eh_frame[] = \n";
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