On 2023/12/26 10:19, Tao Liu wrote:
> 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@xxxxxxxxxx>
> ---
> 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) {
Thank you for looking into this! Looks good to me.
Just a nit, INSTACK() can be used?
Thanks,
Kazu
> prev_sp = bt->bptr + korc->sp_offset;
> framesize = (prev_sp - (rsp + 8) - 8);
> if (CRASHDEBUG(1))
--
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