Hi Tao,
On 2024/12/10 12:39, Tao Liu wrote:
> I can also reproduce this issue on 6.13.0-rc2 machine. The
> mod_symname_hash_install() function missed the case if one spn was
> installed 2 more times, which as a result, will cause the infinite
> loop.
>
> The reason for installing 2 more times is because the addresses
> overlap between 2 kernel modules. See the following:
>
> crash> sym -l
> ffffffffc0800000 MODULE TEXT START: qemu_fw_cfg
> ffffffffc0800000 (t) __pfx_fw_cfg_sysfs_attr_show
> ffffffffc0800010 (t) fw_cfg_sysfs_attr_show
> ...
> ffffffffc0801000 MODULE TEXT START: serio_raw
> ffffffffc0801000 (t) __pfx_serio_raw_poll
> ffffffffc0801000 MODULE TEXT END: qemu_fw_cfg
> ...
> ffffffffc0802000 MODULE TEXT END: serio_raw
>
> For module qemu_fw_cfg, 3 symbols of ffffffffc0801000 will be
> installed. Then for module serio_raw, 3 symbols of ffffffffc0801000
> will be reinstalled. Due to the lack of repeat symbol check, there
> will be symbol reinstall, and infinite loop:
>
> sp->name_hash_next = spn; <<----- name_hash_next point to itself if sp==spn
>
> I think Kazu's "base + size - 1" solution is reasonable, this will let
> qemu_fw_cfg install range from ffffffffc0800000 to
> (ffffffffc0801000-1), so no overlap for 2 modules. In addition, I'd
> like to add the following code as well, to skip if a symbol has
> already been installed:
>
> diff --git a/symbols.c b/symbols.c
> index a26bdc1..e1a62bb 100644
> --- a/symbols.c
> +++ b/symbols.c
> @@ -1233,6 +1233,9 @@ mod_symname_hash_install(struct syment *spn)
> return;
> }
> for (; sp; sp = sp->name_hash_next) {
> + if (spn == sp)
> + return;
> +
> if (!sp->name_hash_next ||
> spn->value < sp->name_hash_next->value) {
> spn->name_hash_next = sp->name_hash_next;
>
> What do you think?
thank you for checking the issue, it's ok to add it for future safety.
Thanks,
Kazu
--
Crash-utility mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxxxxxx
To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxxxxxx
https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/
Contribution Guidelines: https://github.com/crash-utility/crash/wiki
