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Date: Wed, 10 May 2023 19:07:10 +0200
From: Solar Designer <>
Cc: Tobias Holl <>
Subject: Re: Linux kernel io_uring out-of-bounds access to physical memory

On Mon, May 08, 2023 at 04:01:59PM +0200, Tobias Holl wrote:
> TL;DR bug reproduction steps:
>  1. Create a memfd
>  2. fallocate a single page in that file descriptor
>  3. Use MAP_FIXED to map this page repeatedly, in consecutive locations
>  4. Register the entire region that you just filled up with that page as
>     a fixed buffer with IORING_REGISTER_BUFFERS
>  5. Use IORING_OP_WRITE_FIXED to write the buffer to some other file
>     (OOB read) or IORING_OP_READ_FIXED to read data into the buffer (OOB
>     write).
> Of course, from there, we can simply find any interesting object in
> physical memory and start overwriting function pointers to get code
> execution and escalate privileges. A full proof-of-concept exploit with
> a bit more robustness can be found at

I initially overlooked that the exploit was only shared by reference.
Let's have it right in here for archival.  Attached.


View attachment "exploit.c" of type "text/x-c" (25512 bytes)

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