The size of the ring is the product of ring_entries and the size of
struct io_uring_buf. Using struct_size is equivalent to
(ring_entries + 1) * sizeof(struct io_uring_buf)
and generates an off-by-one error. Fix it by using size_mul directly.
Signed-off-by: Tudor Cretu <[email protected]>
---
io_uring/kbuf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 4a6401080c1f..9770757c89a0 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -505,7 +505,7 @@ int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
}
pages = io_pin_pages(reg.ring_addr,
- struct_size(br, bufs, reg.ring_entries),
+ size_mul(sizeof(struct io_uring_buf), reg.ring_entries),
&nr_pages);
if (IS_ERR(pages)) {
kfree(free_bl);
--
2.34.1
On 4/27/23 8:31?AM, Tudor Cretu wrote:
> The size of the ring is the product of ring_entries and the size of
> struct io_uring_buf. Using struct_size is equivalent to
> (ring_entries + 1) * sizeof(struct io_uring_buf)
> and generates an off-by-one error. Fix it by using size_mul directly.
Looks right, so we're doing one entry too much. This is probably a
remnant of when the initial version had it done a bit differently, but
we overlaid the tail with the first entry reserved field.
--
Jens Axboe
On 4/27/23 8:31 AM, Tudor Cretu wrote:
> The size of the ring is the product of ring_entries and the size of
> struct io_uring_buf. Using struct_size is equivalent to
> (ring_entries + 1) * sizeof(struct io_uring_buf)
> and generates an off-by-one error. Fix it by using size_mul directly.
>
> Signed-off-by: Tudor Cretu <[email protected]>
> ---
> io_uring/kbuf.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
> index 4a6401080c1f..9770757c89a0 100644
> --- a/io_uring/kbuf.c
> +++ b/io_uring/kbuf.c
> @@ -505,7 +505,7 @@ int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
> }
>
> pages = io_pin_pages(reg.ring_addr,
> - struct_size(br, bufs, reg.ring_entries),
> + size_mul(sizeof(struct io_uring_buf), reg.ring_entries),
> &nr_pages);
> if (IS_ERR(pages)) {
> kfree(free_bl);
Looking into this again, and some bells ringing in the back of my head,
we do have:
commit 48ba08374e779421ca34bd14b4834aae19fc3e6a
Author: Wojciech Lukowicz <[email protected]>
Date: Sat Feb 18 18:41:41 2023 +0000
io_uring: fix size calculation when registering buf ring
which should have fixed that issue. What kernel version are you looking at?
--
Jens Axboe
On 27-04-2023 19:42, Jens Axboe wrote:
> On 4/27/23 8:31 AM, Tudor Cretu wrote:
>> The size of the ring is the product of ring_entries and the size of
>> struct io_uring_buf. Using struct_size is equivalent to
>> (ring_entries + 1) * sizeof(struct io_uring_buf)
>> and generates an off-by-one error. Fix it by using size_mul directly.
>>
>> Signed-off-by: Tudor Cretu <[email protected]>
>> ---
>> io_uring/kbuf.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
>> index 4a6401080c1f..9770757c89a0 100644
>> --- a/io_uring/kbuf.c
>> +++ b/io_uring/kbuf.c
>> @@ -505,7 +505,7 @@ int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
>> }
>>
>> pages = io_pin_pages(reg.ring_addr,
>> - struct_size(br, bufs, reg.ring_entries),
>> + size_mul(sizeof(struct io_uring_buf), reg.ring_entries),
>> &nr_pages);
>> if (IS_ERR(pages)) {
>> kfree(free_bl);
>
> Looking into this again, and some bells ringing in the back of my head,
> we do have:
>
> commit 48ba08374e779421ca34bd14b4834aae19fc3e6a
> Author: Wojciech Lukowicz <[email protected]>
> Date: Sat Feb 18 18:41:41 2023 +0000
>
> io_uring: fix size calculation when registering buf ring
>
> which should have fixed that issue. What kernel version are you looking at?
Hi Jens,
Thank you for your message. Indeed I was looking at a slightly older
version of the kernel. Apologies for the noise!
Kind regards,
Tudor
>