* Re: [PATCH] stackleak: don't modify ctl_table argument
2024-05-03 13:44 [PATCH] stackleak: don't modify ctl_table argument Thomas Weißschuh
@ 2024-05-03 13:58 ` Tycho Andersen
2024-05-03 17:55 ` Kees Cook
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Tycho Andersen @ 2024-05-03 13:58 UTC (permalink / raw)
To: Thomas Weißschuh
Cc: Kees Cook, Alexander Popov, linux-hardening, linux-kernel, stable,
Luis Chamberlain, Joel Granados
On Fri, May 03, 2024 at 03:44:09PM +0200, Thomas Weißschuh wrote:
> Sysctl handlers are not supposed to modify the ctl_table passed to them.
> Adapt the logic to work with a temporary
> variable, similar to how it is done in other parts of the kernel.
>
> This is also a prerequisite to enforce the immutability of the argument
> through the callbacks prototy.
>
> Fixes: 964c9dff0091 ("stackleak: Allow runtime disabling of kernel stack erasing")
Reviewed-by: Tycho Andersen <tycho@tycho.pizza>
Tycho
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] stackleak: don't modify ctl_table argument
2024-05-03 13:44 [PATCH] stackleak: don't modify ctl_table argument Thomas Weißschuh
2024-05-03 13:58 ` Tycho Andersen
@ 2024-05-03 17:55 ` Kees Cook
2024-05-03 18:24 ` linux
2024-05-03 19:31 ` Kees Cook
2024-05-03 19:35 ` Kees Cook
3 siblings, 1 reply; 6+ messages in thread
From: Kees Cook @ 2024-05-03 17:55 UTC (permalink / raw)
To: Thomas Weißschuh
Cc: Alexander Popov, linux-hardening, linux-kernel, stable,
Luis Chamberlain, Joel Granados
On Fri, May 03, 2024 at 03:44:09PM +0200, Thomas Weißschuh wrote:
> Sysctl handlers are not supposed to modify the ctl_table passed to them.
> Adapt the logic to work with a temporary
> variable, similar to how it is done in other parts of the kernel.
>
> This is also a prerequisite to enforce the immutability of the argument
> through the callbacks prototy.
>
> Fixes: 964c9dff0091 ("stackleak: Allow runtime disabling of kernel stack erasing")
> Cc: stable@vger.kernel.org
I realize I've already Acked, but does this actually need to be CCed
to stable?
> Acked-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---
> This was split out of my sysctl-const-handler series [0].
>
> As that series will take some more time, submit the patch on its own,
> as it is a generic bugfix that is valuable on its own.
> And I can get it out of my books.
>
> Changelog in contrast to the patch in the series:
> * Reword commit message to remove strong relation to the constification
> * Cc stable
>
> [0] https://lore.kernel.org/lkml/20240423-sysctl-const-handler-v3-0-e0beccb836e2@weissschuh.net/
>
> Cc: Joel Granados <j.granados@samsung.com>
> ---
> kernel/stackleak.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/stackleak.c b/kernel/stackleak.c
> index 34c9d81eea94..b292e5ca0b7d 100644
> --- a/kernel/stackleak.c
> +++ b/kernel/stackleak.c
> @@ -27,10 +27,11 @@ static int stack_erasing_sysctl(struct ctl_table *table, int write,
> int ret = 0;
> int state = !static_branch_unlikely(&stack_erasing_bypass);
> int prev_state = state;
> + struct ctl_table tmp = *table;
>
> - table->data = &state;
> - table->maxlen = sizeof(int);
> - ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
> + tmp.data = &state;
> + tmp.maxlen = sizeof(int);
> + ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
> state = !!state;
> if (ret || !write || state == prev_state)
> return ret;
I can pick this up; thanks!
-Kees
>
> ---
> base-commit: f03359bca01bf4372cf2c118cd9a987a5951b1c8
> change-id: 20240503-sysctl-const-stackleak-af3e67bc65b0
>
> Best regards,
> --
> Thomas Weißschuh <linux@weissschuh.net>
>
--
Kees Cook
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] stackleak: don't modify ctl_table argument
2024-05-03 17:55 ` Kees Cook
@ 2024-05-03 18:24 ` linux
0 siblings, 0 replies; 6+ messages in thread
From: linux @ 2024-05-03 18:24 UTC (permalink / raw)
To: Kees Cook
Cc: Thomas Weißschuh, Alexander Popov, linux-hardening,
linux-kernel, stable, Luis Chamberlain, Joel Granados
May 3, 2024 19:55:37 Kees Cook <keescook@chromium.org>:
> On Fri, May 03, 2024 at 03:44:09PM +0200, Thomas Weißschuh wrote:
>> Sysctl handlers are not supposed to modify the ctl_table passed to them.
>> Adapt the logic to work with a temporary
>> variable, similar to how it is done in other parts of the kernel.
>>
>> This is also a prerequisite to enforce the immutability of the argument
>> through the callbacks prototy.
>>
>> Fixes: 964c9dff0091 ("stackleak: Allow runtime disabling of kernel stack erasing")
>> Cc: stable@vger.kernel.org
>
> I realize I've already Acked, but does this actually need to be CCed
> to stable?
You acked it without the Cc stable.
I shouldn't have kept your Ack, sorry.
Feel free to drop the Cc, it shouldn't be critical.
I suspect the bots will pick it up anyways.
>> Acked-by: Kees Cook <keescook@chromium.org>
>> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
>> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
>> ---
>> This was split out of my sysctl-const-handler series [0].
>>
>> As that series will take some more time, submit the patch on its own,
>> as it is a generic bugfix that is valuable on its own.
>> And I can get it out of my books.
>>
>> Changelog in contrast to the patch in the series:
>> * Reword commit message to remove strong relation to the constification
>> * Cc stable
>>
>> [0] https://lore.kernel.org/lkml/20240423-sysctl-const-handler-v3-0-e0beccb836e2@weissschuh.net/
>>
>> Cc: Joel Granados <j.granados@samsung.com>
>> ---
>> kernel/stackleak.c | 7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/stackleak.c b/kernel/stackleak.c
>> index 34c9d81eea94..b292e5ca0b7d 100644
>> --- a/kernel/stackleak.c
>> +++ b/kernel/stackleak.c
>> @@ -27,10 +27,11 @@ static int stack_erasing_sysctl(struct ctl_table *table, int write,
>> int ret = 0;
>> int state = !static_branch_unlikely(&stack_erasing_bypass);
>> int prev_state = state;
>> + struct ctl_table tmp = *table;
>>
>> - table->data = &state;
>> - table->maxlen = sizeof(int);
>> - ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
>> + tmp.data = &state;
>> + tmp.maxlen = sizeof(int);
>> + ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
>> state = !!state;
>> if (ret || !write || state == prev_state)
>> return ret;
>
> I can pick this up; thanks!
Thanks!
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] stackleak: don't modify ctl_table argument
2024-05-03 13:44 [PATCH] stackleak: don't modify ctl_table argument Thomas Weißschuh
2024-05-03 13:58 ` Tycho Andersen
2024-05-03 17:55 ` Kees Cook
@ 2024-05-03 19:31 ` Kees Cook
2024-05-03 19:35 ` Kees Cook
3 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2024-05-03 19:31 UTC (permalink / raw)
To: Thomas Weißschuh
Cc: Alexander Popov, linux-hardening, linux-kernel, stable,
Luis Chamberlain, Joel Granados
On Fri, May 03, 2024 at 03:44:09PM +0200, Thomas Weißschuh wrote:
> Sysctl handlers are not supposed to modify the ctl_table passed to them.
> Adapt the logic to work with a temporary
> variable, similar to how it is done in other parts of the kernel.
>
> This is also a prerequisite to enforce the immutability of the argument
> through the callbacks prototy.
^^^^^^^
Was this supposed to be "prototype"? I couldn't quite figure out what
was meant there; the sentence reads fine to me without the word there at
all. :)
>
> Fixes: 964c9dff0091 ("stackleak: Allow runtime disabling of kernel stack erasing")
> Cc: stable@vger.kernel.org
> Acked-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---
> This was split out of my sysctl-const-handler series [0].
>
> As that series will take some more time, submit the patch on its own,
> as it is a generic bugfix that is valuable on its own.
> And I can get it out of my books.
>
> Changelog in contrast to the patch in the series:
> * Reword commit message to remove strong relation to the constification
> * Cc stable
>
> [0] https://lore.kernel.org/lkml/20240423-sysctl-const-handler-v3-0-e0beccb836e2@weissschuh.net/
>
> Cc: Joel Granados <j.granados@samsung.com>
> ---
> kernel/stackleak.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/stackleak.c b/kernel/stackleak.c
> index 34c9d81eea94..b292e5ca0b7d 100644
> --- a/kernel/stackleak.c
> +++ b/kernel/stackleak.c
> @@ -27,10 +27,11 @@ static int stack_erasing_sysctl(struct ctl_table *table, int write,
> int ret = 0;
> int state = !static_branch_unlikely(&stack_erasing_bypass);
> int prev_state = state;
> + struct ctl_table tmp = *table;
>
> - table->data = &state;
> - table->maxlen = sizeof(int);
> - ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
> + tmp.data = &state;
> + tmp.maxlen = sizeof(int);
> + ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
In looking at this yet again, I can't figure out why maxlen is being
set. It starts its life as sizeof(int):
static struct ctl_table stackleak_sysctls[] = {
{
.procname = "stack_erasing",
.data = NULL,
.maxlen = sizeof(int),
-Kees
> state = !!state;
> if (ret || !write || state == prev_state)
> return ret;
>
> ---
> base-commit: f03359bca01bf4372cf2c118cd9a987a5951b1c8
> change-id: 20240503-sysctl-const-stackleak-af3e67bc65b0
>
> Best regards,
> --
> Thomas Weißschuh <linux@weissschuh.net>
>
--
Kees Cook
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] stackleak: don't modify ctl_table argument
2024-05-03 13:44 [PATCH] stackleak: don't modify ctl_table argument Thomas Weißschuh
` (2 preceding siblings ...)
2024-05-03 19:31 ` Kees Cook
@ 2024-05-03 19:35 ` Kees Cook
3 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2024-05-03 19:35 UTC (permalink / raw)
To: Alexander Popov, Thomas Weißschuh
Cc: Kees Cook, linux-hardening, linux-kernel, stable,
Luis Chamberlain, Joel Granados
On Fri, 03 May 2024 15:44:09 +0200, Thomas Weißschuh wrote:
> Sysctl handlers are not supposed to modify the ctl_table passed to them.
> Adapt the logic to work with a temporary
> variable, similar to how it is done in other parts of the kernel.
>
> This is also a prerequisite to enforce the immutability of the argument
> through the callbacks prototy.
>
> [...]
Applied to for-next/hardening, thanks!
[1/1] stackleak: don't modify ctl_table argument
https://git.kernel.org/kees/c/0e148d3cca0d
Take care,
--
Kees Cook
^ permalink raw reply [flat|nested] 6+ messages in thread