2023-06-14 00:17:35

by Azeem Shaikh

Subject: [PATCH v2] SUNRPC: Remove strlcpy

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with sysfs_emit().

Direct replacement is safe here since the getter in kernel_params_ops
handles -errno return [3].

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89
[3] https://elixir.bootlin.com/linux/v6.4-rc6/source/include/linux/moduleparam.h#L52

Signed-off-by: Azeem Shaikh <[email protected]>
---
net/sunrpc/svc.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index e6d4cec61e47..77326f163801 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -109,13 +109,13 @@ param_get_pool_mode(char *buf, const struct kernel_param *kp)
switch (*ip)
{
case SVC_POOL_AUTO:
- return strlcpy(buf, "auto\n", 20);
+ return sysfs_emit(buf, "auto\n");
case SVC_POOL_GLOBAL:
- return strlcpy(buf, "global\n", 20);
+ return sysfs_emit(buf, "global\n");
case SVC_POOL_PERCPU:
- return strlcpy(buf, "percpu\n", 20);
+ return sysfs_emit(buf, "percpu\n");
case SVC_POOL_PERNODE:
- return strlcpy(buf, "pernode\n", 20);
+ return sysfs_emit(buf, "pernode\n");
default:
return sprintf(buf, "%d\n", *ip);
}
--
2.41.0.162.gfafddb0af9-goog

2023-06-14 01:15:08

by Kees Cook

Subject: Re: [PATCH v2] SUNRPC: Remove strlcpy

On June 13, 2023 5:12:46 PM PDT, Azeem Shaikh <[email protected]> wrote:
>strlcpy() reads the entire source buffer first.
>This read may exceed the destination size limit.
>This is both inefficient and can lead to linear read
>overflows if a source string is not NUL-terminated [1].
>In an effort to remove strlcpy() completely [2], replace
>strlcpy() here with sysfs_emit().
>
>Direct replacement is safe here since the getter in kernel_params_ops
>handles -errno return [3].
>
>[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
>[2] https://github.com/KSPP/linux/issues/89
>[3] https://elixir.bootlin.com/linux/v6.4-rc6/source/include/linux/moduleparam.h#L52
>
>Signed-off-by: Azeem Shaikh <[email protected]>
>---
> net/sunrpc/svc.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
>diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
>index e6d4cec61e47..77326f163801 100644
>--- a/net/sunrpc/svc.c
>+++ b/net/sunrpc/svc.c
>@@ -109,13 +109,13 @@ param_get_pool_mode(char *buf, const struct kernel_param *kp)
> switch (*ip)
> {
> case SVC_POOL_AUTO:
>- return strlcpy(buf, "auto\n", 20);
>+ return sysfs_emit(buf, "auto\n");
> case SVC_POOL_GLOBAL:
>- return strlcpy(buf, "global\n", 20);
>+ return sysfs_emit(buf, "global\n");
> case SVC_POOL_PERCPU:
>- return strlcpy(buf, "percpu\n", 20);
>+ return sysfs_emit(buf, "percpu\n");
> case SVC_POOL_PERNODE:
>- return strlcpy(buf, "pernode\n", 20);
>+ return sysfs_emit(buf, "pernode\n");
> default:
> return sprintf(buf, "%d\n", *ip);

Please replace the sprintf too (and then the Subject could be "use sysfs_emit" or so).

-Kees



--
Kees Cook

2023-06-14 01:16:57

by Azeem Shaikh

Subject: Re: [PATCH v2] SUNRPC: Remove strlcpy

On Tue, Jun 13, 2023 at 9:04 PM Kees Cook <[email protected]> wrote:
>
> On June 13, 2023 5:12:46 PM PDT, Azeem Shaikh <[email protected]> wrote:
> >strlcpy() reads the entire source buffer first.
> >This read may exceed the destination size limit.
> >This is both inefficient and can lead to linear read
> >overflows if a source string is not NUL-terminated [1].
> >In an effort to remove strlcpy() completely [2], replace
> >strlcpy() here with sysfs_emit().
> >
> >Direct replacement is safe here since the getter in kernel_params_ops
> >handles -errno return [3].
> >
> >[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> >[2] https://github.com/KSPP/linux/issues/89
> >[3] https://elixir.bootlin.com/linux/v6.4-rc6/source/include/linux/moduleparam.h#L52
> >
> >Signed-off-by: Azeem Shaikh <[email protected]>
> >---
> > net/sunrpc/svc.c | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
> >diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> >index e6d4cec61e47..77326f163801 100644
> >--- a/net/sunrpc/svc.c
> >+++ b/net/sunrpc/svc.c
> >@@ -109,13 +109,13 @@ param_get_pool_mode(char *buf, const struct kernel_param *kp)
> > switch (*ip)
> > {
> > case SVC_POOL_AUTO:
> >- return strlcpy(buf, "auto\n", 20);
> >+ return sysfs_emit(buf, "auto\n");
> > case SVC_POOL_GLOBAL:
> >- return strlcpy(buf, "global\n", 20);
> >+ return sysfs_emit(buf, "global\n");
> > case SVC_POOL_PERCPU:
> >- return strlcpy(buf, "percpu\n", 20);
> >+ return sysfs_emit(buf, "percpu\n");
> > case SVC_POOL_PERNODE:
> >- return strlcpy(buf, "pernode\n", 20);
> >+ return sysfs_emit(buf, "pernode\n");
> > default:
> > return sprintf(buf, "%d\n", *ip);
>
> Please replace the sprintf too (and then the Subject could be "use sysfs_emit" or so).

Ah sorry, I missed the "replace default sprintf too" part in the
previous thread. Resending.

>
> -Kees
>
>
>
> --
> Kees Cook