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Subject[PATCH v5 5/9] ipc: Clamp semmni to the real IPCMNI limit
Date
For SysV semaphores, the semmni value is the last part of the 4-element
sem number array. To make semmni behave in a similar way to msgmni
and shmmni, we can't directly use the _minmax handler. Instead,
a special sem specific handler is added to check the last argument
to make sure that it is clamped to the [0, IPCMNI] range and prints
a warning message once when an out-of-range value is being written.
This does require duplicating some of the code in the _minmax handlers.

Signed-off-by: Waiman Long <longman@redhat.com>
---
ipc/ipc_sysctl.c | 12 +++++++++++-
ipc/sem.c | 25 +++++++++++++++++++++++++
ipc/util.h | 4 ++++
3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index 088721e..0ad7088 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -88,12 +88,22 @@ 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;
@@ -177,7 +187,7 @@ 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,
},
#ifdef CONFIG_CHECKPOINT_RESTORE
{
diff --git a/ipc/sem.c b/ipc/sem.c
index a4af049..faf2caa 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -2337,3 +2337,28 @@ 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;
+
+ /*
+ * 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_ratelimited("sysctl: \"sem[3]\" was set out of range [%d, %d], clamped to %d.\n",
+ 0, IPCMNI, ns->sc_semmni);
+}
+#endif
diff --git a/ipc/util.h b/ipc/util.h
index 89b8ec1..af57394 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -206,6 +206,10 @@ int ipcget(struct ipc_namespace *ns, struct ipc_ids *ids,
void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
void (*free)(struct ipc_namespace *, struct kern_ipc_perm *));

+#ifdef CONFIG_PROC_SYSCTL
+extern void sem_check_semmni(struct ctl_table *table, struct ipc_namespace *ns);
+#endif
+
#ifdef CONFIG_COMPAT
#include <linux/compat.h>
struct compat_ipc_perm {
--
1.8.3.1
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