> On Jun 13, 2023, at 3:42 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > > On Tue, Jun 13, 2023 at 02:18:06PM +0000, Chuck Lever III wrote: >> >> >>> On Jun 12, 2023, at 8:40 PM, Azeem Shaikh <azeemshaikh38@xxxxxxxxx> 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 strscpy(). >> >> Using sprintf() seems cleaner to me: it would get rid of >> the undocumented naked integer. Would that work for you? > > This is changing the "get" routine for reporting module parameters out > of /sys. I think the right choice here is sysfs_emit(), as it performs > the size tracking correctly. (Even the "default" sprintf() call should > be replaced too, IMO.) Agreed, that's even better. >>> Direct replacement is safe here since the getter in kernel_params_ops >>> handles -errorno return [3]. >> >> s/errorno/errno/ >> >> >>> [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 <azeemshaikh38@xxxxxxxxx> >>> --- >>> 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..e5f379c4fdb3 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 strscpy(buf, "auto\n", 20); > > e.g. > return sysfs_emit(buf, "auto\n"); > ... > >>> case SVC_POOL_GLOBAL: >>> - return strlcpy(buf, "global\n", 20); >>> + return strscpy(buf, "global\n", 20); >>> case SVC_POOL_PERCPU: >>> - return strlcpy(buf, "percpu\n", 20); >>> + return strscpy(buf, "percpu\n", 20); >>> case SVC_POOL_PERNODE: >>> - return strlcpy(buf, "pernode\n", 20); >>> + return strscpy(buf, "pernode\n", 20); >>> default: >>> return sprintf(buf, "%d\n", *ip); > > and: > > return sysfs_emit(buf, "%d\n", *ip); > > > -Kees > > -- > Kees Cook -- Chuck Lever
