coredump: make core dump functionality optional

Adds an expert Kconfig option, CONFIG_COREDUMP, which allows disabling of
core dump.  This saves approximately 2.6k in the compiled kernel, and
complements CONFIG_ELF_CORE, which now depends on it.

CONFIG_COREDUMP also disables coredump-related sysctls, except for
suid_dumpable and related functions, which are necessary for ptrace.

[akpm@linux-foundation.org: fix binfmt_aout.c build]
Signed-off-by: Alex Kelly <alex.page.kelly@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 1 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 84c76a34e41c..c2a2f8084bad 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -97,10 +97,12 @@
 extern int sysctl_overcommit_memory;
 extern int sysctl_overcommit_ratio;
 extern int max_threads;
-extern int core_uses_pid;
 extern int suid_dumpable;
+#ifdef CONFIG_COREDUMP
+extern int core_uses_pid;
 extern char core_pattern[];
 extern unsigned int core_pipe_limit;
+#endif
 extern int pid_max;
 extern int min_free_kbytes;
 extern int pid_max_min, pid_max_max;
@@ -177,8 +179,10 @@ static int proc_dointvec_minmax_sysadmin(struct ctl_table *table, int write,
 
 static int proc_dointvec_minmax_coredump(struct ctl_table *table, int write,
                 void __user *buffer, size_t *lenp, loff_t *ppos);
+#ifdef CONFIG_COREDUMP
 static int proc_dostring_coredump(struct ctl_table *table, int write,
                 void __user *buffer, size_t *lenp, loff_t *ppos);
+#endif
 
 #ifdef CONFIG_MAGIC_SYSRQ
 /* Note: sysrq code uses it's own private copy */
@@ -404,6 +408,7 @@ static struct ctl_table kern_table[] = {
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec,
         },
+#ifdef CONFIG_COREDUMP
         {
                 .procname       = "core_uses_pid",
                 .data           = &core_uses_pid,
@@ -425,6 +430,7 @@ static struct ctl_table kern_table[] = {
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec,
         },
+#endif
 #ifdef CONFIG_PROC_SYSCTL
         {
                 .procname       = "tainted",
@@ -2036,12 +2042,14 @@ int proc_dointvec_minmax(struct ctl_table *table, int write,
 
 static void validate_coredump_safety(void)
 {
+#ifdef CONFIG_COREDUMP
         if (suid_dumpable == SUID_DUMPABLE_SAFE &&
             core_pattern[0] != '/' && core_pattern[0] != '|') {
                 printk(KERN_WARNING "Unsafe core_pattern used with "\
                         "suid_dumpable=2. Pipe handler or fully qualified "\
                         "core dump path required.\n");
         }
+#endif
 }
 
 static int proc_dointvec_minmax_coredump(struct ctl_table *table, int write,
@@ -2053,6 +2061,7 @@ static int proc_dointvec_minmax_coredump(struct ctl_table *table, int write,
         return error;
 }
 
+#ifdef CONFIG_COREDUMP
 static int proc_dostring_coredump(struct ctl_table *table, int write,
                   void __user *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -2061,6 +2070,7 @@ static int proc_dostring_coredump(struct ctl_table *table, int write,
                 validate_coredump_safety();
         return error;
 }
+#endif
 
 static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int write,
                                      void __user *buffer,