Merge tag 'random_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull /dev/random bug fix from Ted Ts'o:
 "Fix a race on architectures with prioritized interrupts (such as m68k)
  which can causes crashes in drivers/char/random.c:get_reg()"

* tag 'random_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  fix race in drivers/char/random.c:get_reg()

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 0ab024918907..a561f0c2f428 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1097,12 +1097,16 @@ static void add_interrupt_bench(cycles_t start)
 static __u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
 {
         __u32 *ptr = (__u32 *) regs;
+        unsigned long flags;
 
         if (regs == NULL)
                 return 0;
+        local_irq_save(flags);
         if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32))
                 f->reg_idx = 0;
-        return *(ptr + f->reg_idx++);
+        ptr += f->reg_idx++;
+        local_irq_restore(flags);
+        return *ptr;
 }
 
 void add_interrupt_randomness(int irq, int irq_flags)