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SubjectRe: [PATCH v3 6/6] ipc: Clamp semmni to the real IPCMNI limit
On Thu, Mar 01, 2018 at 12:43:40PM -0500, Waiman Long wrote:
> This patch clamps the semmni value (fourth element of sem_ctls[]
> array) to within the [0, IPCMNI] range and prints a warning message
> once when an out-of-range value is being written.
>
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
> ipc/ipc_sysctl.c | 13 ++++++++++++-
> ipc/sem.c | 28 ++++++++++++++++++++++++++++
> ipc/util.h | 4 ++++
> 3 files changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
> index 8eb7268..2c03f57 100644
> --- a/ipc/ipc_sysctl.c
> +++ b/ipc/ipc_sysctl.c
> @@ -97,12 +97,22 @@ static int proc_ipc_auto_msgmni(struct ctl_table *table, int write,
> return proc_dointvec_minmax(&ipc_table, write, buffer, lenp, ppos);
> }
>
> +static int proc_ipc_sem_dointvec(struct ctl_table *table, int write,
> + void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> + int ret = proc_ipc_dointvec(table, write, buffer, lenp, ppos);
> +
> + sem_check_semmni(table, current->nsproxy->ipc_ns);
> + return ret;
> +}
> +
> #else
> #define proc_ipc_doulongvec_minmax NULL
> #define proc_ipc_dointvec NULL
> #define proc_ipc_dointvec_minmax NULL
> #define proc_ipc_dointvec_minmax_orphans NULL
> #define proc_ipc_auto_msgmni NULL
> +#define proc_ipc_sem_dointvec NULL
> #endif
>
> static int zero;
> @@ -186,7 +196,8 @@ static int proc_ipc_auto_msgmni(struct ctl_table *table, int write,
> .data = &init_ipc_ns.sem_ctls,
> .maxlen = 4*sizeof(int),
> .mode = 0644,
> - .proc_handler = proc_ipc_dointvec,
> + .proc_handler = proc_ipc_sem_dointvec,
> + .flags = CTL_FLAGS_CLAMP_RANGE,
> },
> #ifdef CONFIG_CHECKPOINT_RESTORE
> {
> diff --git a/ipc/sem.c b/ipc/sem.c
> index a4af049..739dfca 100644
> --- a/ipc/sem.c
> +++ b/ipc/sem.c
> @@ -2337,3 +2337,31 @@ static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
> return 0;
> }
> #endif
> +
> +#ifdef CONFIG_PROC_SYSCTL
> +/*
> + * Check to see if semmni is out of range and clamp it if necessary.
> + */
> +void sem_check_semmni(struct ctl_table *table, struct ipc_namespace *ns)
> +{
> + bool clamped = false;
> +
> + if (!(table->flags & CTL_FLAGS_CLAMP_RANGE))
> + return;
> +
> + /*
> + * Clamp semmni to the range [0, IPCMNI].
> + */
> + if (ns->sc_semmni < 0) {
> + ns->sc_semmni = 0;
> + clamped = true;
> + }
> + if (ns->sc_semmni > IPCMNI) {
> + ns->sc_semmni = IPCMNI;
> + clamped = true;
> + }
> + if (clamped)
> + pr_warn_once("Kernel parameter \"sem[3]\" was set out of range [%d, %d], clamped to %d.\n",
> + 0, IPCMNI, ns->sc_semmni);

Why are the users issuing a warning, wouldn't the API do the warning
on its own, specially since we're adding a warn flag?

Luis

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