6266 harden dtrace_difo_chunksize() with respect to malicious DIF

Reviewed by: Alex Wilson <alex.wilson@joyent.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Approved by: Garrett D'Amore <garrett@damore.org>

1 files changed, 59 insertions, 8 deletions

diff --git a/usr/src/uts/common/dtrace/dtrace.c b/usr/src/uts/common/dtrace/dtrace.c
index aa4b1d67e0..f2c3fec010 100644
--- a/usr/src/uts/common/dtrace/dtrace.c
+++ b/usr/src/uts/common/dtrace/dtrace.c
@@ -118,7 +118,7 @@ int		dtrace_destructive_disallow = 0;
 dtrace_optval_t	dtrace_nonroot_maxsize = (16 * 1024 * 1024);
 size_t		dtrace_difo_maxsize = (256 * 1024);
 dtrace_optval_t	dtrace_dof_maxsize = (8 * 1024 * 1024);
-size_t		dtrace_global_maxsize = (16 * 1024);
+size_t		dtrace_statvar_maxsize = (16 * 1024);
 size_t		dtrace_actions_max = (16 * 1024);
 size_t		dtrace_retain_max = 1024;
 dtrace_optval_t	dtrace_helper_actions_max = 1024;
@@ -592,13 +592,33 @@ dtrace_canstore_statvar(uint64_t addr, size_t sz,
     dtrace_statvar_t **svars, int nsvars)
 {
 	int i;
+	size_t maxglobalsize, maxlocalsize;
+
+	if (nsvars == 0)
+		return (0);
+
+	maxglobalsize = dtrace_statvar_maxsize;
+	maxlocalsize = (maxglobalsize + sizeof (uint64_t)) * NCPU;
 
 	for (i = 0; i < nsvars; i++) {
 		dtrace_statvar_t *svar = svars[i];
+		uint8_t scope;
+		size_t size;
 
-		if (svar == NULL || svar->dtsv_size == 0)
+		if (svar == NULL || (size = svar->dtsv_size) == 0)
 			continue;
 
+		scope = svar->dtsv_var.dtdv_scope;
+
+		/*
+		 * We verify that our size is valid in the spirit of providing
+		 * defense in depth:  we want to prevent attackers from using
+		 * DTrace to escalate an orthogonal kernel heap corruption bug
+		 * into the ability to store to arbitrary locations in memory.
+		 */
+		VERIFY((scope == DIFV_SCOPE_GLOBAL && size < maxglobalsize) ||
+		    (scope == DIFV_SCOPE_LOCAL && size < maxlocalsize));
+
 		if (DTRACE_INRANGE(addr, sz, svar->dtsv_data, svar->dtsv_size))
 			return (1);
 	}
@@ -4165,7 +4185,8 @@ dtrace_dif_subr(uint_t subr, uint_t rd, uint64_t *regs,
 
 		if (!dtrace_destructive_disallow &&
 		    dtrace_priv_proc_control(state, mstate) &&
-		    !dtrace_istoxic(kaddr, size)) {
+		    !dtrace_istoxic(kaddr, size) &&
+		    dtrace_canload(kaddr, size, mstate, vstate)) {
 			DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
 			dtrace_copyout(kaddr, uaddr, size, flags);
 			DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
@@ -4180,7 +4201,8 @@ dtrace_dif_subr(uint_t subr, uint_t rd, uint64_t *regs,
 
 		if (!dtrace_destructive_disallow &&
 		    dtrace_priv_proc_control(state, mstate) &&
-		    !dtrace_istoxic(kaddr, size)) {
+		    !dtrace_istoxic(kaddr, size) &&
+		    dtrace_strcanload(kaddr, size, mstate, vstate)) {
 			DTRACE_CPUFLAG_SET(CPU_DTRACE_NOFAULT);
 			dtrace_copyoutstr(kaddr, uaddr, size, flags);
 			DTRACE_CPUFLAG_CLEAR(CPU_DTRACE_NOFAULT);
@@ -6078,6 +6100,11 @@ dtrace_dif_emulate(dtrace_difo_t *difo, dtrace_mstate_t *mstate,
 				    regs[r2] ? regs[r2] :
 				    dtrace_strsize_default) + 1;
 			} else {
+				if (regs[r2] > LONG_MAX) {
+					*flags |= CPU_DTRACE_ILLOP;
+					break;
+				}
+
 				tupregs[ttop].dttk_size = regs[r2];
 			}
 
@@ -9344,9 +9371,10 @@ dtrace_difo_validate(dtrace_difo_t *dp, dtrace_vstate_t *vstate, uint_t nregs,
 				break;
 			}
 
-			if (v->dtdv_scope == DIFV_SCOPE_GLOBAL &&
-			    vt->dtdt_size > dtrace_global_maxsize) {
-				err += efunc(i, "oversized by-ref global\n");
+			if ((v->dtdv_scope == DIFV_SCOPE_GLOBAL ||
+			    v->dtdv_scope == DIFV_SCOPE_LOCAL) &&
+			    vt->dtdt_size > dtrace_statvar_maxsize) {
+				err += efunc(i, "oversized by-ref static\n");
 				break;
 			}
 		}
@@ -9683,6 +9711,9 @@ dtrace_difo_chunksize(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
 				if (srd == 0)
 					return;
 
+				if (sval > LONG_MAX)
+					return;
+
 				tupregs[ttop++].dttk_size = sval;
 			}
 
@@ -9744,6 +9775,19 @@ dtrace_difo_chunksize(dtrace_difo_t *dp, dtrace_vstate_t *vstate)
 		 */
 		size = P2ROUNDUP(size, sizeof (uint64_t));
 
+		/*
+		 * Before setting the chunk size, check that we're not going
+		 * to set it to a negative value...
+		 */
+		if (size > LONG_MAX)
+			return;
+
+		/*
+		 * ...and make certain that we didn't badly overflow.
+		 */
+		if (size < ksize || size < sizeof (dtrace_dynvar_t))
+			return;
+
 		if (size > vstate->dtvs_dynvars.dtds_chunksize)
 			vstate->dtvs_dynvars.dtds_chunksize = size;
 	}
@@ -13184,6 +13228,8 @@ dtrace_dstate_init(dtrace_dstate_t *dstate, size_t size)
 	if ((dstate->dtds_chunksize = chunksize) == 0)
 		dstate->dtds_chunksize = DTRACE_DYNVAR_CHUNKSIZE;
 
+	VERIFY(dstate->dtds_chunksize < LONG_MAX);
+
 	if (size < (min = dstate->dtds_chunksize + sizeof (dtrace_dynhash_t)))
 		size = min;
 
@@ -13224,6 +13270,9 @@ dtrace_dstate_init(dtrace_dstate_t *dstate, size_t size)
 	    ((uintptr_t)base + hashsize * sizeof (dtrace_dynhash_t));
 	limit = (uintptr_t)base + size;
 
+	VERIFY((uintptr_t)start < limit);
+	VERIFY((uintptr_t)start >= (uintptr_t)base);
+
 	maxper = (limit - (uintptr_t)start) / NCPU;
 	maxper = (maxper / dstate->dtds_chunksize) * dstate->dtds_chunksize;
 
@@ -13245,7 +13294,7 @@ dtrace_dstate_init(dtrace_dstate_t *dstate, size_t size)
 			start = (dtrace_dynvar_t *)limit;
 		}
 
-		ASSERT(limit <= (uintptr_t)base + size);
+		VERIFY(limit <= (uintptr_t)base + size);
 
 		for (;;) {
 			next = (dtrace_dynvar_t *)((uintptr_t)dvar +
@@ -13254,6 +13303,8 @@ dtrace_dstate_init(dtrace_dstate_t *dstate, size_t size)
 			if ((uintptr_t)next + dstate->dtds_chunksize >= limit)
 				break;
 
+			VERIFY((uintptr_t)dvar >= (uintptr_t)base &&
+			    (uintptr_t)dvar <= (uintptr_t)base + size);
 			dvar->dtdv_next = next;
 			dvar = next;
 		}