2023-09-08 16:00:36

by Song Shuai

Subject: [PATCH] of/kexec: Omit kaslr-seed when kexecing with nokaslr

The chosen node always adds the kaslr-seed property which is needless
for the kernels kexeced with the cmdline contained "nokaslr".

So omit the kaslr-seed when kexecing with nokaslr.

Signed-off-by: Song Shuai <[email protected]>
---
drivers/of/kexec.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
index f26d2ba8a371..c0d53b10cb70 100644
--- a/drivers/of/kexec.c
+++ b/drivers/of/kexec.c
@@ -19,6 +19,7 @@
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/types.h>
+#include <linux/string.h>

#define RNG_SEED_SIZE 128

@@ -263,6 +264,14 @@ static inline int setup_ima_buffer(const struct kimage *image, void *fdt,
}
#endif /* CONFIG_IMA_KEXEC */

+static bool is_nokaslr_cmdline(const char *cmdline)
+{
+ char *str;
+
+ str = strstr(cmdline, "nokaslr");
+ return str == cmdline || (str > cmdline && *(str - 1) == ' ');
+}
+
/*
* of_kexec_alloc_and_setup_fdt - Alloc and setup a new Flattened Device Tree
*
@@ -429,15 +438,15 @@ void *of_kexec_alloc_and_setup_fdt(const struct kimage *image,
else if (ret)
goto out;

- if (rng_is_initialized()) {
+ if (!is_nokaslr_cmdline(cmdline) && rng_is_initialized()) {
u64 seed = get_random_u64();

ret = fdt_setprop_u64(fdt, chosen_node, "kaslr-seed", seed);
if (ret)
goto out;
} else {
- pr_notice("RNG is not initialised: omitting \"%s\" property\n",
- "kaslr-seed");
+ pr_notice("RNG is not initialised or Kexec with nokaslr:"
+ " omitting \"%s\" property\n", "kaslr-seed");
}

/* add rng-seed */
--
2.20.1

2023-09-08 19:32:01

by Rob Herring

Subject: Re: [PATCH] of/kexec: Omit kaslr-seed when kexecing with nokaslr

On Fri, Sep 8, 2023 at 5:45 AM Song Shuai <[email protected]> wrote:
>
> The chosen node always adds the kaslr-seed property which is needless
> for the kernels kexeced with the cmdline contained "nokaslr".
>
> So omit the kaslr-seed when kexecing with nokaslr.

The kexec'ed kernel can ignore bootargs with CONFIG_CMDLINE_FORCE. So
you don't know if kaslr-seed will be used or not.

> Signed-off-by: Song Shuai <[email protected]>
> ---
> drivers/of/kexec.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
> index f26d2ba8a371..c0d53b10cb70 100644
> --- a/drivers/of/kexec.c
> +++ b/drivers/of/kexec.c
> @@ -19,6 +19,7 @@
> #include <linux/random.h>
> #include <linux/slab.h>
> #include <linux/types.h>
> +#include <linux/string.h>
>
> #define RNG_SEED_SIZE 128
>
> @@ -263,6 +264,14 @@ static inline int setup_ima_buffer(const struct kimage *image, void *fdt,
> }
> #endif /* CONFIG_IMA_KEXEC */
>
> +static bool is_nokaslr_cmdline(const char *cmdline)
> +{
> + char *str;
> +
> + str = strstr(cmdline, "nokaslr");
> + return str == cmdline || (str > cmdline && *(str - 1) == ' ');

Yet another copy of the same code. That's a clue to refactor into a
common function.

Rob