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Message-ID: <01af059f-bbab-4f3f-9c45-43f8802999c8.xulu@allwinnertech.com>
Date: Mon, 04 Jun 2018 16:45:28 +0800
From: "徐露" <xulu@...winnertech.com>
To: "musl" <musl@...ts.openwall.com>
Subject: SIGSEGV and SIGILL at malloc/free on ARM926
Hi all,
I use Openwrt project and the version of musl libc is 1.1.16.
I have been experiencing random crashes when running customer's application.
From the coredump files, the segfault looks like a memory corruption issue. But when I add some malloc and free log, the issues did not occur.
After analyzing several coredump files, I found that the last bit of cszie in chunk has seemed to be set from 1 to 0.
This is very strange and I don't have many ideas how to go further.
Could you please give us some pointers, thanks! I can supply more details as needed.
This is the unbin and free function from src/malloc/malloc.c.
224 static void unbin(struct chunk *c, int i)
225 {
226 if (c->prev == c->next)
227 a_and_64(&mal.binmap, ~(1ULL<<i));
228 c->prev->next = c->next;
229 c->next->prev = c->prev;
230 c->csize |= C_INUSE;
231 NEXT_CHUNK(c)->psize |= C_INUSE;
232 }
450 void free(void *p)
451 {
452 struct chunk *self = MEM_TO_CHUNK(p);
453 struct chunk *next;
454 size_t final_size, new_size, size;
455 int reclaim=0;
456 int i;
457
458 if (!p) return;
459
460 if (IS_MMAPPED(self)) {
461 size_t extra = self->psize;
462 char *base = (char *)self - extra;
463 size_t len = CHUNK_SIZE(self) + extra;
464 /* Crash on double free */
465 if (extra & 1) a_crash();
466 __munmap(base, len);
467 return;
468 }
......
531 }
Here are some backtraces and memory dump I got.
1) In this case, the coredump shows that c->prev->next is the error. But from the memory context, the csize of chunk(0x1d12608) should be 0x31, not 0x30.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x0045e20c in unbin (c=c@...ry=0x1d12608, i=i@...ry=2) at src/malloc/malloc.c:228
228 src/malloc/malloc.c: 没有那个文件或目录.
(gdb) bt
#0 0x0045e20c in unbin (c=c@...ry=0x1d12608, i=i@...ry=2) at src/malloc/malloc.c:228
#1 0x0045e34c in alloc_fwd (c=c@...ry=0x1d12608) at src/malloc/malloc.c:242
#2 0x0045e48c in free (p=<optimized out>) at src/malloc/malloc.c:497
#3 0x003d77e4 in lh_table_free ()
#4 0x003d05ac in json_object_object_delete ()
#5 0x003cff00 in json_object_put ()
#6 0x003d0580 in json_object_lh_entry_free ()
#7 0x003d77b4 in lh_table_free ()
#8 0x003d05ac in json_object_object_delete ()
#9 0x003cff00 in json_object_put ()
#10 0x00248b98 in msgHandleLoop(void*) ()
#11 0x00471a40 in start (p=0xb687cd34) at src/thread/pthread_create.c:145
(gdb) x/64wa 0x1d125a8
0x1d125a8: 0x1d125c0 0x0 0x0 0x0
0x1d125b8: 0x31 0x41 0x10 0x1
0x1d125c8: 0x0 0x0 0x2 0x1
0x1d125d8: 0x0 0x0 0x1d6aaa0 0x1d6aaa0
0x1d125e8: 0x1d6aa70 0x3d0550 <json_object_lh_entry_free> 0x3d7410 <lh_char_hash> 0x3d7484 <lh_char_equal>
0x1d125f8: 0x41 0x11 0x60ed00 <mal+8> 0x60ed00 <mal+8>
0x1d12608: 0x11 0x30 0x4 0x3d058c <json_object_object_delete>
0x1d12618: 0x3d02f0 <json_object_object_to_json_string> 0x1 0x0 0x0
0x1d12628: 0x1d12c60 0x0 0x0 0x0
0x1d12638: 0x31 0x11 0x1d125f8 0x1d12610
0x1d12648: 0x11 0x21 0x646e6576 0x735f726f
0x1d12658: 0x75746174 0x3d0073 <json_object_set_serializer+22> 0x3d7410 <lh_char_hash> 0x3d7484 <lh_char_equal>
0x1d12668: 0x21 0x20 0x60ed10 <mal+24> 0x1d13318
0x1d12678: 0x736d65 0x0 0x0 0x0
0x1d12688: 0x20 0x21 0x1cc9f20 0x1d07050
0x1d12698: 0x1d12640 0x0 0x0 0x0
2) In this case, the coredump shows that c->prev->next is the error. But from the memory context, the csize of chunk(0x1d12608) should be 0x21, not 0x20.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x0045e20c in unbin (c=c@...ry=0x1127518, i=i@...ry=1) at src/malloc/malloc.c:228
228 src/malloc/malloc.c: 没有那个文件或目录.
(gdb) bt
#0 0x0045e20c in unbin (c=c@...ry=0x1127518, i=i@...ry=1) at src/malloc/malloc.c:228
#1 0x0045e34c in alloc_fwd (c=c@...ry=0x1127518) at src/malloc/malloc.c:242
#2 0x0045e48c in free (p=<optimized out>) at src/malloc/malloc.c:497
#3 0x00051cd0 in hook_free ()
#4 0x00045388 in cJSON_Delete ()
#5 0x000453e0 in cJSON_Delete ()
#6 0x000453e0 in cJSON_Delete ()
#7 0x000453e0 in cJSON_Delete ()
#8 0x000453e0 in cJSON_Delete ()
#9 0x000453e0 in cJSON_Delete ()
#10 0x00053258 in _vendor_stub_json_handle_status ()
#11 0x0005376c in _vendor_stub_json_handle_battery_status_cloud ()
#12 0x00054c74 in _vendor_stub_json_recv_thread_parse_json ()
#13 0x00054e20 in _vendor_stub_json_recv_thread ()
#14 0x00471a40 in start (p=0xb6bdad34) at src/thread/pthread_create.c:145
(gdb) x/64wa 0x11274e8
0x11274e8: 0x11 0x21 0x756e694c 0x600078
0x11274f8: 0x10f5700 0x5 0x0 0x0
0x1127508: 0x21 0x11 0x63726570 0x746e65
0x1127518: 0x11 0x20 0x706f7270 0x79747265
0x1127528: 0x0 0x3ff00000 0x1127540 0x0
0x1127538: 0x21 0x41 0x10d3e30 0x10dce40
0x1127548: 0x0 0x3 0x0 0x5c
0x1127558: 0x0 0x40570000 0x10d3e20 0x0
0x1127568: 0x0 0x0 0x10dce00 0x0
0x1127578: 0x41 0x31 0x10f57d0 0x13c
0x1127588: 0x1 0x36d060 <av_buffer_default_free> 0x0 0x2
0x1127598: 0x0 0x36d060 <av_buffer_default_free> 0x0 0x2
0x11275a8: 0x31 0x991 0xf38ffbca 0xe404eab5
0x11275b8: 0xe087e0fe 0xe246e0df 0xedf1e714 0xfa4af4a6
0x11275c8: 0x4ffff58 0xcc40a13 0xd730d15 0xeb30ed1
0x11275d8: 0xa450c55 0x87c0975 0x24a05eb 0xfe1cffbb
3) In this case, from the memory context, the csize of chunk(0x7b81d8) should be 0x31, not 0x30.
Program terminated with signal SIGILL, Illegal instruction.
#0 0x0045e320 in a_crash () at src/malloc/malloc.c:465
465 src/malloc/malloc.c: 没有那个文件或目录.
(gdb) bt
#0 0x0045e320 in a_crash () at src/malloc/malloc.c:465
#1 free (p=0x7b81e0) at src/malloc/malloc.c:465
#2 0x003cfeb8 in json_object_generic_delete ()
#3 0x003d052c in json_object_object_delete ()
#4 0x003cfe78 in json_object_put ()
#5 0x003d04f8 in json_object_lh_entry_free ()
#6 0x003d772c in lh_table_free ()
#7 0x003d0524 in json_object_object_delete ()
#8 0x003cfe78 in json_object_put ()
#9 0x0024aa1c in ServerAdapter::sendTextMsg(char const*, char const*, int, json_object*) ()
#10 0x00240658 in ServerEvent::incrementSync(json_object*) ()
#11 0x002476e0 in HostAdapter::onHandleNotifyMsg(json_object*) ()
#12 0x00248c90 in msgHandleLoop(void*) ()
#13 0x004719b8 in start (p=0xb679ed34) at src/thread/pthread_create.c:145
(gdb) x/64wa 0x7b81a8
0x7b81a8: 0x3d1280 <json_object_string_to_json_string> 0x0 0x0 0x0
0x7b81b8: 0x7b97e0 0x3 0x0 0x0
0x7b81c8: 0x140 0x11 0x61726170 0x736d params
0x7b81d8: 0x11 0x30 0x4 0x3d0504 <json_object_object_delete>
0x7b81e8: 0x3d0268 <json_object_object_to_json_string> 0x0 0x0 0x0
0x7b81f8: 0x7b8210 0x0 0x0 0x0
0x7b8208: 0x31 0x40 0x60ed30 <mal+56> 0x60ed30 <mal+56>
0x7b8218: 0x0 0x0 0x1 0x1
0x7b8228: 0x0 0x0 0x7b7910 0x7b7910
0x7b8238: 0x7b78a0 0x3d04c8 <json_object_lh_entry_free> 0x3d7388 <lh_char_hash> 0x3d73fc <lh_char_equal>
0x7b8248: 0x40 0x21 0x6c796170 0x64616f <ff_cos_65536+90991>
0x7b8258: 0x736d65 0x0 0xffffffff 0x0
0x7b8268: 0x21 0x100 0x60edf0 <mal+248> 0x60edf0 <mal+248>
0x7b8278: 0x3d1574 <json_object_array_to_json_string> 0x0 0x0 0x0
0x7b8288: 0x7b82a0 0x0 0x0 0x0
0x7b8298: 0x31 0xd1 0x60edc0 <mal+200> 0x60edc0 <mal+200>
Best regards！
—————————————————————
徐 露
全志科技 事业一部
MOBI：+86 13425063650
ADDR：广东省珠海市高新区唐家湾镇科技2路9号
MAIL：xulu@...winnertech.com
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