On Thu, Aug 29, 2019 at 11:48 AM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> Anybody?
This is ENTIRELY UNTESTED.
Anybody willing to test and take ownership?
Linus
include/linux/kfifo.h | 12 ++++++++----
lib/kfifo.c | 4 +++-
2 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
index fc4b0b10210f..078f52c20aad 100644
--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -117,6 +117,12 @@ struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2, void);
*/
#define DECLARE_KFIFO(fifo, type, size) STRUCT_KFIFO(type, size) fifo
+#define VERIFY_POWER_OF2(x) \
+ ((x)+BUILD_BUG_ON_ZERO((x) & ((x)-1)))
+
+#define __KFIFO_MASK_SIZE(fifo) \
+ (__is_kfifo_ptr(&(fifo)) ? 0 : VERIFY_POWER_OF2(ARRAY_SIZE((fifo).buf)) - 1)
+
/**
* INIT_KFIFO - Initialize a fifo declared by DECLARE_KFIFO
* @fifo: name of the declared fifo datatype
@@ -127,7 +133,7 @@ struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2, void);
struct __kfifo *__kfifo = &__tmp->kfifo; \
__kfifo->in = 0; \
__kfifo->out = 0; \
- __kfifo->mask = __is_kfifo_ptr(__tmp) ? 0 : ARRAY_SIZE(__tmp->buf) - 1;\
+ __kfifo->mask = __KFIFO_MASK_SIZE(fifo); \
__kfifo->esize = sizeof(*__tmp->buf); \
__kfifo->data = __is_kfifo_ptr(__tmp) ? NULL : __tmp->buf; \
})
@@ -147,9 +153,7 @@ struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2, void);
{ \
.in = 0, \
.out = 0, \
- .mask = __is_kfifo_ptr(&(fifo)) ? \
- 0 : \
- ARRAY_SIZE((fifo).buf) - 1, \
+ .mask = __KFIFO_MASK_SIZE(fifo), \
.esize = sizeof(*(fifo).buf), \
.data = __is_kfifo_ptr(&(fifo)) ? \
NULL : \
diff --git a/lib/kfifo.c b/lib/kfifo.c
index 117ad0e7fbf4..7f145cb41e6d 100644
--- a/lib/kfifo.c
+++ b/lib/kfifo.c
@@ -68,7 +68,9 @@ int __kfifo_init(struct __kfifo *fifo, void *buffer,
{
size /= esize;
- size = roundup_pow_of_two(size);
+ /* Warn because we had a bug here and would round up */
+ if (WARN_ON_ONCE(!is_power_of_2(size)))
+ size = rounddown_pow_of_two(size);
fifo->in = 0;
fifo->out = 0;
