coredump masking: reimplementation of dumpable using two flags

This patch changes mm_struct.dumpable to a pair of bit flags.

set_dumpable() converts three-value dumpable to two flags and stores it into
lower two bits of mm_struct.flags instead of mm_struct.dumpable.
get_dumpable() behaves in the opposite way.

[akpm@linux-foundation.org: export set_dumpable]
Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 10 insertions, 3 deletions

diff --git a/include/asm-ia64/processor.h b/include/asm-ia64/processor.h
index db81ba406cef..6251c76437d2 100644
--- a/include/asm-ia64/processor.h
+++ b/include/asm-ia64/processor.h
@@ -295,9 +295,9 @@ struct thread_struct {
         regs->ar_bspstore = current->thread.rbs_bot;                                            \
         regs->ar_fpsr = FPSR_DEFAULT;                                                           \
         regs->loadrs = 0;                                                                       \
-        regs->r8 = current->mm->dumpable;       /* set "don't zap registers" flag */            \
+        regs->r8 = get_dumpable(current->mm);   /* set "don't zap registers" flag */            \
         regs->r12 = new_sp - 16;        /* allocate 16 byte scratch area */                     \
-        if (unlikely(!current->mm->dumpable)) {                                                 \
+        if (unlikely(!get_dumpable(current->mm))) {                                                     \
                 /*                                                                              \
                  * Zap scratch regs to avoid leaking bits between processes with different      \
                  * uid/privileges.                                                              \
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 731edaca8ffd..8dbd08366400 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -345,6 +345,13 @@ typedef unsigned long mm_counter_t;
                 (mm)->hiwater_vm = (mm)->total_vm;      \
 } while (0)
 
+extern void set_dumpable(struct mm_struct *mm, int value);
+extern int get_dumpable(struct mm_struct *mm);
+
+/* mm flags */
+#define MMF_DUMPABLE      0  /* core dump is permitted */
+#define MMF_DUMP_SECURELY 1  /* core file is readable only by root */
+
 struct mm_struct {
         struct vm_area_struct * mmap;           /* list of VMAs */
         struct rb_root mm_rb;
@@ -402,7 +409,7 @@ struct mm_struct {
         unsigned int token_priority;
         unsigned int last_interval;
 
-        unsigned char dumpable:2;
+        unsigned long flags; /* Must use atomic bitops to access the bits */
 
         /* coredumping support */
         int core_waiters;