diff options
| author | Theodore Ts'o <tytso@mit.edu> | 2017-06-07 19:01:32 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-04-13 19:50:24 +0200 |
| commit | 031987b6beaa02f64aa4428329e34ee3c5b3c76f (patch) | |
| tree | a738f88d7dd437ef4a3e80730a2cd4693b33e70f | |
| parent | db203ab2402dbb9b58b038b8f9097a997f4d8a76 (diff) | |
random: use lockless method of accessing and updating f->reg_idx
commit 92e75428ffc90e2a0321062379f883f3671cfebe upstream.
Linus pointed out that there is a much more efficient way of avoiding
the problem that we were trying to address in commit 9dfa7bba35ac0:
"fix race in drivers/char/random.c:get_reg()".
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/char/random.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 29b4218e9b63..bd9fc2baa6aa 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -886,15 +886,15 @@ 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; + unsigned int idx; if (regs == NULL) return 0; - local_irq_save(flags); - if (f->reg_idx >= sizeof(struct pt_regs) / sizeof(__u32)) - f->reg_idx = 0; - ptr += f->reg_idx++; - local_irq_restore(flags); + idx = READ_ONCE(f->reg_idx); + if (idx >= sizeof(struct pt_regs) / sizeof(__u32)) + idx = 0; + ptr += idx++; + WRITE_ONCE(f->reg_idx, idx); return *ptr; } |