Previously the value of bt->bptr is not checked, which may led to a wrong prev_sp and framesize. As a result, bt->stackbuf[] will be accessed out of range, and segfault. Before: crash> set debug 1 crash> bt ...snip... --- <NMI exception stack> --- #8 [ffffffff9a603e10] __switch_to_asm at ffffffff99800214 rsp: ffffffff9a603e10 textaddr: ffffffff99800214 -> spo: 0 bpo: 0 spr: 0 bpr: 0 type: 0 end: 0 #9 [ffffffff9a603e40] __schedule at ffffffff9960dfb1 rsp: ffffffff9a603e40 textaddr: ffffffff9960dfb1 -> spo: 16 bpo: -16 spr: 4 bpr: 1 type: 0 end: 0 rsp: ffffffff9a603e40 rbp: ffffb9ca076e7ca8 prev_sp: ffffb9ca076e7cb8 framesize: 1829650024 Segmentation fault (core dumped) (gdb) p/x bt->stackbase $1 = 0xffffffff9a600000 (gdb) p/x bt->stacktop $2 = 0xffffffff9a604000 After: crash> set debug 1 crash> bt ...snip... --- <NMI exception stack> --- #8 [ffffffff9a603e10] __switch_to_asm at ffffffff99800214 rsp: ffffffff9a603e10 textaddr: ffffffff99800214 -> spo: 0 bpo: 0 spr: 0 bpr: 0 type: 0 end: 0 #9 [ffffffff9a603e40] __schedule at ffffffff9960dfb1 rsp: ffffffff9a603e40 textaddr: ffffffff9960dfb1 -> spo: 16 bpo: -16 spr: 4 bpr: 1 type: 0 end: 0 #10 [ffffffff9a603e98] schedule_idle at ffffffff9960e87c rsp: ffffffff9a603e98 textaddr: ffffffff9960e87c -> spo: 8 bpo: 0 spr: 5 bpr: 0 type: 0 end: 0 rsp: ffffffff9a603e98 prev_sp: ffffffff9a603ea8 framesize: 0 ...snip... This patch will check bt->bptr value before calculate framesize. Only bt->bptr falls into the range of bt->stackbase and bt->stacktop will be regarded as valid. Signed-off-by: Tao Liu <ltao(a)redhat.com&gt; --- x86_64.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/x86_64.c b/x86_64.c index 8abe39d..ff1ba6e 100644 --- a/x86_64.c +++ b/x86_64.c @@ -8707,7 +8707,8 @@ x86_64_get_framesize(struct bt_info *bt, ulong textaddr, ulong rsp, char *stack_ if (CRASHDEBUG(1)) fprintf(fp, "rsp: %lx prev_sp: %lx framesize: %d\n", rsp, prev_sp, framesize); - } else if ((korc->sp_reg == ORC_REG_BP) && bt->bptr) { + } else if ((korc->sp_reg == ORC_REG_BP) && bt->bptr && + bt->bptr >= bt->stackbase && bt->bptr <= bt->stacktop) { prev_sp = bt->bptr + korc->sp_offset; framesize = (prev_sp - (rsp + 8) - 8); if (CRASHDEBUG(1)) -- 2.40.1