linux-kernel - Re: Strange EFAULT on mips64el returned by syscall when another thread is forking

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Message-ID: <0625c3286a515ccb2ff5f7f58fd2019f81dd512e.camel@xry111.site>
Date: Thu, 25 Jan 2024 05:38:16 +0800
From: Xi Ruoyao <xry111@...111.site>
To: Andreas Schwab <schwab@...e.de>, Ben Hutchings <ben@...adent.org.uk>
Cc: linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org, Jiaxun Yang
 <jiaxun.yang@...goat.com>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
  libc-alpha@...rceware.org, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: Strange EFAULT on mips64el returned by syscall when another
 thread is forking

On Thu, 2024-01-25 at 05:32 +0800, Xi Ruoyao wrote:

/* snip */

> and the "interesting" aspects:
> 
> 1. If I change the third parameter of "read" to any value >= 8, it no
> longer fails.  But it fails with any integer in [1, 8).
> 2. It fails no matter if I initialize buf.
> 3. It does not fail on arm64 (the only other port using
> lock_mm_and_find_vma I have access to).

Correction: I'd not realized many ports use lock_mm_and_find_vma even
before this series of changes.  I also have access to x86_64 and
loongarch64, and the failure seems specific to MIPS.

-- 
Xi Ruoyao <xry111@...111.site>
School of Aerospace Science and Technology, Xidian University