Hi Tao,
Thank you for the patch, this tested ok on my end.
Thanks!
Kazu
On 2025/01/23 20:11, Tao Liu wrote:
> The "pcp" and "spp" can be NULL for "bt -S/-I", but the value is not
> checked before pointer dereference, which lead to segfault error.
> This patch fix this by delay the pointer dereference after
> x86_64_get_dumpfile_stack_frame().
>
> Before:
> crash> bt -S ffffbccee0087ab8
> PID: 2179 TASK: ffffa0f78912a3c0 CPU: 43 COMMAND: "bash"
> Segmentation fault (core dumped)
>
> After:
> crash> bt -S ffffbccee0087ab8
> PID: 2179 TASK: ffffa0f78912a3c0 CPU: 43 COMMAND: "bash"
> #0 [ffffbccee0087b10] __crash_kexec at ffffffffad20c30a
> #1 [ffffbccee0087bd0] panic at ffffffffadcbce30
> #2 [ffffbccee0087c50] sysrq_handle_crash at ffffffffad802b86
> ...
>
> Signed-off-by: Tao Liu <ltao@xxxxxxxxxx>
> ---
> x86_64.c | 36 ++++++++++++++++++------------------
> 1 file changed, 18 insertions(+), 18 deletions(-)
>
> diff --git a/x86_64.c b/x86_64.c
> index c254c6e..d4bbd15 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -5009,16 +5009,11 @@ static void
> x86_64_get_stack_frame(struct bt_info *bt, ulong *pcp, ulong *spp)
> {
> struct user_regs_bitmap_struct *ur_bitmap;
> - ulong pcp_save = *pcp;
> - ulong spp_save = *spp;
> - ulong sp;
> + ulong sp = 0;
>
> if (bt->flags & BT_SKIP_IDLE)
> bt->flags &= ~BT_SKIP_IDLE;
> - if (pcp)
> - *pcp = x86_64_get_pc(bt);
> - if (spp)
> - sp = *spp = x86_64_get_sp(bt);
> +
> ur_bitmap = (struct user_regs_bitmap_struct *)GETBUF(sizeof(*ur_bitmap));
> memset(ur_bitmap, 0, sizeof(*ur_bitmap));
>
> @@ -5091,31 +5086,36 @@ x86_64_get_stack_frame(struct bt_info *bt, ulong *pcp, ulong *spp)
> if (bt->flags & BT_DUMPFILE_SEARCH) {
> FREEBUF(ur_bitmap);
> bt->need_free = FALSE;
> - *pcp = pcp_save;
> - *spp = spp_save;
> return x86_64_get_dumpfile_stack_frame(bt, pcp, spp);
> }
> }
> } else {
> if (!is_task_active(bt->task)) {
> - readmem(*spp, KVADDR, &(ur_bitmap->ur.bp),
> - sizeof(ulong), "ur_bitmap->ur.bp", FAULT_ON_ERROR);
> - SET_REG_BITMAP(ur_bitmap->bitmap, x86_64_user_regs_struct, bp);
> + if (spp) {
> + *spp = x86_64_get_sp(bt);
> + readmem(*spp, KVADDR, &(ur_bitmap->ur.bp),
> + sizeof(ulong), "ur_bitmap->ur.bp", FAULT_ON_ERROR);
> + SET_REG_BITMAP(ur_bitmap->bitmap, x86_64_user_regs_struct, bp);
> + }
> } else {
> if (bt->flags & BT_DUMPFILE_SEARCH) {
> FREEBUF(ur_bitmap);
> bt->need_free = FALSE;
> - *pcp = pcp_save;
> - *spp = spp_save;
> return x86_64_get_dumpfile_stack_frame(bt, pcp, spp);
> }
> }
> }
>
> - ur_bitmap->ur.ip = *pcp;
> - ur_bitmap->ur.sp = sp;
> - SET_REG_BITMAP(ur_bitmap->bitmap, x86_64_user_regs_struct, ip);
> - SET_REG_BITMAP(ur_bitmap->bitmap, x86_64_user_regs_struct, sp);
> + if (pcp) {
> + *pcp = x86_64_get_pc(bt);
> + ur_bitmap->ur.ip = *pcp;
> + SET_REG_BITMAP(ur_bitmap->bitmap, x86_64_user_regs_struct, ip);
> + }
> + if (spp) {
> + *spp = x86_64_get_sp(bt);
> + ur_bitmap->ur.sp = sp + *spp;
> + SET_REG_BITMAP(ur_bitmap->bitmap, x86_64_user_regs_struct, sp);
> + }
>
> bt->machdep = ur_bitmap;
> bt->need_free = TRUE;
--
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