coredump: kill MMF_DUMPABLE and MMF_DUMP_SECURELY

[linux.git] / fs / exec.c

diff --git a/fs/exec.c b/fs/exec.c
index 7ea097f6b341f06982f3ea3b068de5755b1605e0..f798da06abac5c33724914b28b6bbe85f3420765 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1613,52 +1613,24 @@ void set_binfmt(struct linux_binfmt *new)
 EXPORT_SYMBOL(set_binfmt);
 
 /*
- * set_dumpable converts traditional three-value dumpable to two flags and
- * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
- * these bits are not changed atomically.  So get_dumpable can observe the
- * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
- * return either old dumpable or new one by paying attention to the order of
- * modifying the bits.
- *
- * dumpable |   mm->flags (binary)
- * old  new | initial interim  final
- * ---------+-----------------------
- *  0    1  |   00      01      01
- *  0    2  |   00      10(*)   11
- *  1    0  |   01      00      00
- *  1    2  |   01      11      11
- *  2    0  |   11      10(*)   00
- *  2    1  |   11      11      01
- *
- * (*) get_dumpable regards interim value of 10 as 11.
+ * set_dumpable stores three-value SUID_DUMP_* into mm->flags.
  */
 void set_dumpable(struct mm_struct *mm, int value)
 {
-       switch (value) {
-       case SUID_DUMP_DISABLE:
-               clear_bit(MMF_DUMPABLE, &mm->flags);
-               smp_wmb();
-               clear_bit(MMF_DUMP_SECURELY, &mm->flags);
-               break;
-       case SUID_DUMP_USER:
-               set_bit(MMF_DUMPABLE, &mm->flags);
-               smp_wmb();
-               clear_bit(MMF_DUMP_SECURELY, &mm->flags);
-               break;
-       case SUID_DUMP_ROOT:
-               set_bit(MMF_DUMP_SECURELY, &mm->flags);
-               smp_wmb();
-               set_bit(MMF_DUMPABLE, &mm->flags);
-               break;
-       }
+       unsigned long old, new;
+
+       if (WARN_ON((unsigned)value > SUID_DUMP_ROOT))
+               return;
+
+       do {
+               old = ACCESS_ONCE(mm->flags);
+               new = (old & ~MMF_DUMPABLE_MASK) | value;
+       } while (cmpxchg(&mm->flags, old, new) != old);
 }
 
 int __get_dumpable(unsigned long mm_flags)
 {
-       int ret;
-
-       ret = mm_flags & MMF_DUMPABLE_MASK;
-       return (ret > SUID_DUMP_USER) ? SUID_DUMP_ROOT : ret;
+       return mm_flags & MMF_DUMPABLE_MASK;
 }
 
 /*