linux-kernel - [PATCH 06/14] arch/tile: prevent corrupt top frame from causing backtracer runaway

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <dabe98c972091818762e02841ab1f982e573e7d0.1287090286.git.cmetcalf@tilera.com>
Date:	Thu, 14 Oct 2010 15:19:04 -0400
From:	Chris Metcalf <cmetcalf@...era.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:	Arnd Bergmann <arnd@...db.de>
Subject: [PATCH 06/14] arch/tile: prevent corrupt top frame from causing backtracer runaway

The backtracer will normally cut itself off after 100 frames anyway,
but it's messy.  With this change we notice that the frame being
reported is the same as the last one, and cut off the dump with a
message similar to what gdb displays in the same circumstance.

Signed-off-by: Chris Metcalf <cmetcalf@...era.com>
---
 arch/tile/kernel/stack.c |   35 ++++++++++++++++++++++-------------
 1 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/arch/tile/kernel/stack.c b/arch/tile/kernel/stack.c
index ea2e0ce..0d54106 100644
--- a/arch/tile/kernel/stack.c
+++ b/arch/tile/kernel/stack.c
@@ -30,6 +30,10 @@
 #include <arch/abi.h>
 #include <arch/interrupts.h>
 
+#define KBT_ONGOING	0  /* Backtrace still ongoing */
+#define KBT_DONE	1  /* Backtrace cleanly completed */
+#define KBT_RUNNING	2  /* Can't run backtrace on a running task */
+#define KBT_LOOP	3  /* Backtrace entered a loop */
 
 /* Is address on the specified kernel stack? */
 static int in_kernel_stack(struct KBacktraceIterator *kbt, VirtualAddress sp)
@@ -207,11 +211,11 @@ static int KBacktraceIterator_next_item_inclusive(
 	for (;;) {
 		do {
 			if (!KBacktraceIterator_is_sigreturn(kbt))
-				return 1;
+				return KBT_ONGOING;
 		} while (backtrace_next(&kbt->it));
 
 		if (!KBacktraceIterator_restart(kbt))
-			return 0;
+			return KBT_DONE;
 	}
 }
 
@@ -264,7 +268,7 @@ void KBacktraceIterator_init(struct KBacktraceIterator *kbt,
 	kbt->pgtable = NULL;
 	kbt->verbose = 0;   /* override in caller if desired */
 	kbt->profile = 0;   /* override in caller if desired */
-	kbt->end = 0;
+	kbt->end = KBT_ONGOING;
 	kbt->new_context = 0;
 	if (is_current) {
 		HV_PhysAddr pgdir_pa = hv_inquire_context().page_table;
@@ -290,7 +294,7 @@ void KBacktraceIterator_init(struct KBacktraceIterator *kbt,
 	if (regs == NULL) {
 		if (is_current || t->state == TASK_RUNNING) {
 			/* Can't do this; we need registers */
-			kbt->end = 1;
+			kbt->end = KBT_RUNNING;
 			return;
 		}
 		pc = get_switch_to_pc();
@@ -305,26 +309,29 @@ void KBacktraceIterator_init(struct KBacktraceIterator *kbt,
 	}
 
 	backtrace_init(&kbt->it, read_memory_func, kbt, pc, lr, sp, r52);
-	kbt->end = !KBacktraceIterator_next_item_inclusive(kbt);
+	kbt->end = KBacktraceIterator_next_item_inclusive(kbt);
 }
 EXPORT_SYMBOL(KBacktraceIterator_init);
 
 int KBacktraceIterator_end(struct KBacktraceIterator *kbt)
 {
-	return kbt->end;
+	return kbt->end != KBT_ONGOING;
 }
 EXPORT_SYMBOL(KBacktraceIterator_end);
 
 void KBacktraceIterator_next(struct KBacktraceIterator *kbt)
 {
+	VirtualAddress old_pc = kbt->it.pc, old_sp = kbt->it.sp;
 	kbt->new_context = 0;
-	if (!backtrace_next(&kbt->it) &&
-	    !KBacktraceIterator_restart(kbt)) {
-			kbt->end = 1;
-			return;
-		}
-
-	kbt->end = !KBacktraceIterator_next_item_inclusive(kbt);
+	if (!backtrace_next(&kbt->it) && !KBacktraceIterator_restart(kbt)) {
+		kbt->end = KBT_DONE;
+		return;
+	}
+	kbt->end = KBacktraceIterator_next_item_inclusive(kbt);
+	if (old_pc == kbt->it.pc && old_sp == kbt->it.sp) {
+		/* Trapped in a loop; give up. */
+		kbt->end = KBT_LOOP;
+	}
 }
 EXPORT_SYMBOL(KBacktraceIterator_next);
 
@@ -387,6 +394,8 @@ void tile_show_stack(struct KBacktraceIterator *kbt, int headers)
 			break;
 		}
 	}
+	if (kbt->end == KBT_LOOP)
+		pr_err("Stack dump stopped; next frame identical to this one\n");
 	if (headers)
 		pr_err("Stack dump complete\n");
 }
-- 
1.6.5.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/