fs/proc/namespaces.c: prevent crash when ns_entries[] is empty

If CONFIG_NET_NS, CONFIG_UTS_NS and CONFIG_IPC_NS are disabled,
ns_entries[] becomes empty and things like
ns_entries[ARRAY_SIZE(ns_entries) - 1] will explode.

Reported-by: Richard Weinberger <richard@nod.at>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Daniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index 3551f1f..0d9e23a 100644 (file)
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -156,15 +156,15 @@ static struct dentry *proc_ns_dir_lookup(struct inode *dir,
        if (!ptrace_may_access(task, PTRACE_MODE_READ))
                goto out;
 
-       last = &ns_entries[ARRAY_SIZE(ns_entries) - 1];
-       for (entry = ns_entries; entry <= last; entry++) {
+       last = &ns_entries[ARRAY_SIZE(ns_entries)];
+       for (entry = ns_entries; entry < last; entry++) {
                if (strlen((*entry)->name) != len)
                        continue;
                if (!memcmp(dentry->d_name.name, (*entry)->name, len))
                        break;
        }
        error = ERR_PTR(-ENOENT);
-       if (entry > last)
+       if (entry == last)
                goto out;
 
        error = proc_ns_instantiate(dir, dentry, task, *entry);