Hi all,
Ping guys. Any comments or objections?
On Wed, May 25, 2022 at 2:51 PM Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote:
>
> Setting ->proc_handler to proc_dobool at the same time setting ->maxlen
> to sizeof(int) is counter-intuitive, it is easy to make mistakes in the
> future (When I first use proc_dobool() in my driver, I assign
> sizeof(variable) to table->maxlen. Then I found it was wrong, it should
> be sizeof(int) which was very counter-intuitive). For robustness,
> rework proc_dobool() robustly. So it is an improvement not a real bug
> fix.
>
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Iurii Zaikin <yzaikin@xxxxxxxxxx>
> ---
> v3:
> - Update commit log.
>
> v2:
> - Reimplementing proc_dobool().
>
> fs/lockd/svc.c | 2 +-
> kernel/sysctl.c | 38 +++++++++++++++++++-------------------
> 2 files changed, 20 insertions(+), 20 deletions(-)
>
> diff --git a/fs/lockd/svc.c b/fs/lockd/svc.c
> index 59ef8a1f843f..6e48ee787f49 100644
> --- a/fs/lockd/svc.c
> +++ b/fs/lockd/svc.c
> @@ -496,7 +496,7 @@ static struct ctl_table nlm_sysctls[] = {
> {
> .procname = "nsm_use_hostnames",
> .data = &nsm_use_hostnames,
> - .maxlen = sizeof(int),
> + .maxlen = sizeof(nsm_use_hostnames),
> .mode = 0644,
> .proc_handler = proc_dobool,
> },
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index e52b6e372c60..50a2c29efc94 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -423,21 +423,6 @@ static void proc_put_char(void **buf, size_t *size, char c)
> }
> }
>
> -static int do_proc_dobool_conv(bool *negp, unsigned long *lvalp,
> - int *valp,
> - int write, void *data)
> -{
> - if (write) {
> - *(bool *)valp = *lvalp;
> - } else {
> - int val = *(bool *)valp;
> -
> - *lvalp = (unsigned long)val;
> - *negp = false;
> - }
> - return 0;
> -}
> -
> static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
> int *valp,
> int write, void *data)
> @@ -708,16 +693,31 @@ int do_proc_douintvec(struct ctl_table *table, int write,
> * @lenp: the size of the user buffer
> * @ppos: file position
> *
> - * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
> - * values from/to the user buffer, treated as an ASCII string.
> + * Reads/writes up to table->maxlen/sizeof(bool) bool values from/to
> + * the user buffer, treated as an ASCII string.
> *
> * Returns 0 on success.
> */
> int proc_dobool(struct ctl_table *table, int write, void *buffer,
> size_t *lenp, loff_t *ppos)
> {
> - return do_proc_dointvec(table, write, buffer, lenp, ppos,
> - do_proc_dobool_conv, NULL);
> + struct ctl_table tmp = *table;
> + bool *data = table->data;
> + unsigned int val = READ_ONCE(*data);
> + int ret;
> +
> + /* Do not support arrays yet. */
> + if (table->maxlen != sizeof(bool))
> + return -EINVAL;
> +
> + tmp.maxlen = sizeof(val);
> + tmp.data = &val;
> + ret = do_proc_douintvec(&tmp, write, buffer, lenp, ppos, NULL, NULL);
> + if (ret)
> + return ret;
> + if (write)
> + WRITE_ONCE(*data, val ? true : false);
> + return 0;
> }
>
> /**
> --
> 2.11.0
>
