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>

6 files changed, 53 insertions, 27 deletions

diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
index 022574202749..0efd1524b977 100644
--- a/fs/Kconfig.binfmt
+++ b/fs/Kconfig.binfmt
@@ -164,3 +164,11 @@ config BINFMT_MISC
           You may say M here for module support and later load the module when
           you have use for it; the module is called binfmt_misc. If you
           don't know what to answer at this point, say Y.
+
+config COREDUMP
+        bool "Enable core dump support" if EXPERT
+        default y
+        help
+          This option enables support for performing core dumps. You almost
+          certainly want to say Y here. Not necessary on systems that never
+          need debugging or only ever run flawless code.
diff --git a/fs/Makefile b/fs/Makefile
index 8938f8250320..1d7af79288a0 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -11,7 +11,7 @@ obj-y :=	open.o read_write.o file_table.o super.o \
                 attr.o bad_inode.o file.o filesystems.o namespace.o \
                 seq_file.o xattr.o libfs.o fs-writeback.o \
                 pnode.o drop_caches.o splice.o sync.o utimes.o \
-                stack.o fs_struct.o statfs.o coredump.o
+                stack.o fs_struct.o statfs.o
 
 ifeq ($(CONFIG_BLOCK),y)
 obj-y +=        buffer.o bio.o block_dev.o direct-io.o mpage.o ioprio.o
@@ -48,6 +48,7 @@ obj-$(CONFIG_FS_MBCACHE)	+= mbcache.o
 obj-$(CONFIG_FS_POSIX_ACL)      += posix_acl.o xattr_acl.o
 obj-$(CONFIG_NFS_COMMON)        += nfs_common/
 obj-$(CONFIG_GENERIC_ACL)       += generic_acl.o
+obj-$(CONFIG_COREDUMP)          += coredump.o
 
 obj-$(CONFIG_FHANDLE)           += fhandle.o
 
diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
index d146e181d10d..4b5b5117f00a 100644
--- a/fs/binfmt_aout.c
+++ b/fs/binfmt_aout.c
@@ -32,31 +32,8 @@
 
 static int load_aout_binary(struct linux_binprm *, struct pt_regs * regs);
 static int load_aout_library(struct file*);
-static int aout_core_dump(struct coredump_params *cprm);
-
-static struct linux_binfmt aout_format = {
-        .module         = THIS_MODULE,
-        .load_binary    = load_aout_binary,
-        .load_shlib     = load_aout_library,
-        .core_dump      = aout_core_dump,
-        .min_coredump   = PAGE_SIZE
-};
-
-#define BAD_ADDR(x)     ((unsigned long)(x) >= TASK_SIZE)
-
-static int set_brk(unsigned long start, unsigned long end)
-{
-        start = PAGE_ALIGN(start);
-        end = PAGE_ALIGN(end);
-        if (end > start) {
-                unsigned long addr;
-                addr = vm_brk(start, end - start);
-                if (BAD_ADDR(addr))
-                        return addr;
-        }
-        return 0;
-}
 
+#ifdef CONFIG_COREDUMP
 /*
  * Routine writes a core dump image in the current directory.
  * Currently only a stub-function.
@@ -66,7 +43,6 @@ static int set_brk(unsigned long start, unsigned long end)
  * field, which also makes sure the core-dumps won't be recursive if the
  * dumping of the process results in another error..
  */
-
 static int aout_core_dump(struct coredump_params *cprm)
 {
         struct file *file = cprm->file;
@@ -135,6 +111,32 @@ end_coredump:
         set_fs(fs);
         return has_dumped;
 }
+#else
+#define aout_core_dump NULL
+#endif
+
+static struct linux_binfmt aout_format = {
+        .module         = THIS_MODULE,
+        .load_binary    = load_aout_binary,
+        .load_shlib     = load_aout_library,
+        .core_dump      = aout_core_dump,
+        .min_coredump   = PAGE_SIZE
+};
+
+#define BAD_ADDR(x)     ((unsigned long)(x) >= TASK_SIZE)
+
+static int set_brk(unsigned long start, unsigned long end)
+{
+        start = PAGE_ALIGN(start);
+        end = PAGE_ALIGN(end);
+        if (end > start) {
+                unsigned long addr;
+                addr = vm_brk(start, end - start);
+                if (BAD_ADDR(addr))
+                        return addr;
+        }
+        return 0;
+}
 
 /*
  * create_aout_tables() parses the env- and arg-strings in new user
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 366422bc1633..00e2e8908953 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -132,7 +132,11 @@ extern int copy_strings_kernel(int argc, const char *const *argv,
                                struct linux_binprm *bprm);
 extern int prepare_bprm_creds(struct linux_binprm *bprm);
 extern void install_exec_creds(struct linux_binprm *bprm);
+#ifdef CONFIG_COREDUMP
 extern void do_coredump(long signr, int exit_code, struct pt_regs *regs);
+#else
+static inline void do_coredump(long signr, int exit_code, struct pt_regs *regs) {}
+#endif
 extern void set_binfmt(struct linux_binfmt *new);
 extern void free_bprm(struct linux_binprm *);
 
diff --git a/init/Kconfig b/init/Kconfig
index e82f289290fa..ed6334dd5e71 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1199,6 +1199,7 @@ config BUG
           Just say Y.
 
 config ELF_CORE
+        depends on COREDUMP
         default y
         bool "Enable ELF core dumps" if EXPERT
         help
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,