lkml.org 
[lkml]   [2021]   [May]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: Memory uninitialized after "io_uring: keep table of pointers to ubufs"
From
Date
On 5/29/21 1:33 AM, Andres Freund wrote:
> Hi,
>
> I started to see buffer registration randomly failing with ENOMEM on
> 5.13. Registering buffer or two often succeeds, but more than that
> rarely. Running the same program as root succeeds - but the user has a high
> rlimit.
>
> The issue is that io_sqe_buffer_register() doesn't initialize
> imu. io_buffer_account_pin() does imu->acct_pages++, before calling
> io_account_mem(ctx, imu->acct_pages);
>
> Which means that a random amount of memory is being accounted for. On the first
> few allocations this sometimes fails to fail because the memory is zero, but
> after a bit of reuse...

Makes sense, thanks for digging in. I've just sent a patch, would
be great if you can test it or send your own.


> It only doesn't fail as root because the rlimit doesn't apply.
>
> This is caused by
>
> commit 41edf1a5ec967bf4bddedb83c48e02dfea8315b4
> Author: Pavel Begunkov <asml.silence@gmail.com>
> Date: 2021-04-25 14:32:23 +0100
>
> io_uring: keep table of pointers to ubufs
>
> Greetings,
>
> Andres Freund
>

--
Pavel Begunkov

\
 
 \ /
  Last update: 2021-05-29 13:04    [W:0.067 / U:0.276 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site