2018-06-29 18:59:38

by Kees Cook

Subject: [PATCH] EDAC, thunderx: Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this
switches to using a kmalloc-allocated buffer instead of stack space.
This should be fine since the existing routine is allocating memory
too.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Cc: David Daney <[email protected]>
Cc: Jan Glauber <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Mauro Carvalho Chehab <[email protected]>
Cc: [email protected]
Signed-off-by: Kees Cook <[email protected]>
---
drivers/edac/thunderx_edac.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/edac/thunderx_edac.c b/drivers/edac/thunderx_edac.c
index 4803c6468bab..c009d94f40c5 100644
--- a/drivers/edac/thunderx_edac.c
+++ b/drivers/edac/thunderx_edac.c
@@ -408,26 +408,29 @@ static ssize_t thunderx_lmc_inject_ecc_write(struct file *file,
size_t count, loff_t *ppos)
{
struct thunderx_lmc *lmc = file->private_data;
-
unsigned int cline_size = cache_line_size();
-
- u8 tmp[cline_size];
+ u8 *tmp;
void __iomem *addr;
unsigned int offs, timeout = 100000;

atomic_set(&lmc->ecc_int, 0);

lmc->mem = alloc_pages_node(lmc->node, GFP_KERNEL, 0);
-
if (!lmc->mem)
return -ENOMEM;

+ tmp = kmalloc(cline_size, GFP_KERNEL);
+ if (!tmp) {
+ __free_pages(lmc->mem, 0);
+ return -ENOMEM;
+ }
+
addr = page_address(lmc->mem);

while (!atomic_read(&lmc->ecc_int) && timeout--) {
stop_machine(inject_ecc_fn, lmc, NULL);

- for (offs = 0; offs < PAGE_SIZE; offs += sizeof(tmp)) {
+ for (offs = 0; offs < PAGE_SIZE; offs += cline_size) {
/*
* Do a load from the previously rigged location
* This should generate an error interrupt.
@@ -437,6 +440,7 @@ static ssize_t thunderx_lmc_inject_ecc_write(struct file *file,
}
}

+ kfree(tmp);
__free_pages(lmc->mem, 0);

return count;
--
2.17.1


--
Kees Cook
Pixel Security

2018-07-06 11:43:13

by Jan Glauber

Subject: Re: [PATCH] EDAC, thunderx: Remove VLA usage

On Fri, Jun 29, 2018 at 11:48:50AM -0700, Kees Cook wrote:
> In the quest to remove all stack VLA usage from the kernel[1], this
> switches to using a kmalloc-allocated buffer instead of stack space.
> This should be fine since the existing routine is allocating memory
> too.
>
> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>
> Cc: David Daney <[email protected]>
> Cc: Jan Glauber <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: Mauro Carvalho Chehab <[email protected]>
> Cc: [email protected]
> Signed-off-by: Kees Cook <[email protected]>

Acked-by: Jan Glauber <[email protected]>

thanks,
Jan

> ---
> drivers/edac/thunderx_edac.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/edac/thunderx_edac.c b/drivers/edac/thunderx_edac.c
> index 4803c6468bab..c009d94f40c5 100644
> --- a/drivers/edac/thunderx_edac.c
> +++ b/drivers/edac/thunderx_edac.c
> @@ -408,26 +408,29 @@ static ssize_t thunderx_lmc_inject_ecc_write(struct file *file,
> size_t count, loff_t *ppos)
> {
> struct thunderx_lmc *lmc = file->private_data;
> -
> unsigned int cline_size = cache_line_size();
> -
> - u8 tmp[cline_size];
> + u8 *tmp;
> void __iomem *addr;
> unsigned int offs, timeout = 100000;
>
> atomic_set(&lmc->ecc_int, 0);
>
> lmc->mem = alloc_pages_node(lmc->node, GFP_KERNEL, 0);
> -
> if (!lmc->mem)
> return -ENOMEM;
>
> + tmp = kmalloc(cline_size, GFP_KERNEL);
> + if (!tmp) {
> + __free_pages(lmc->mem, 0);
> + return -ENOMEM;
> + }
> +
> addr = page_address(lmc->mem);
>
> while (!atomic_read(&lmc->ecc_int) && timeout--) {
> stop_machine(inject_ecc_fn, lmc, NULL);
>
> - for (offs = 0; offs < PAGE_SIZE; offs += sizeof(tmp)) {
> + for (offs = 0; offs < PAGE_SIZE; offs += cline_size) {
> /*
> * Do a load from the previously rigged location
> * This should generate an error interrupt.
> @@ -437,6 +440,7 @@ static ssize_t thunderx_lmc_inject_ecc_write(struct file *file,
> }
> }
>
> + kfree(tmp);
> __free_pages(lmc->mem, 0);
>
> return count;
> --
> 2.17.1
>
>
> --
> Kees Cook
> Pixel Security

2018-07-09 09:39:45

by Borislav Petkov

Subject: Re: [PATCH] EDAC, thunderx: Remove VLA usage

On Fri, Jul 06, 2018 at 01:42:16PM +0200, Jan Glauber wrote:
> On Fri, Jun 29, 2018 at 11:48:50AM -0700, Kees Cook wrote:
> > In the quest to remove all stack VLA usage from the kernel[1], this
> > switches to using a kmalloc-allocated buffer instead of stack space.
> > This should be fine since the existing routine is allocating memory
> > too.
> >
> > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
> >
> > Cc: David Daney <[email protected]>
> > Cc: Jan Glauber <[email protected]>
> > Cc: Borislav Petkov <[email protected]>
> > Cc: Mauro Carvalho Chehab <[email protected]>
> > Cc: [email protected]
> > Signed-off-by: Kees Cook <[email protected]>
>
> Acked-by: Jan Glauber <[email protected]>

Applied, thanks.

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
--