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SubjectRe: Memory uninitialized after "io_uring: keep table of pointers to ubufs"
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 <>
> Date: 2021-04-25 14:32:23 +0100
> io_uring: keep table of pointers to ubufs
> Greetings,
> Andres Freund

Pavel Begunkov

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