archive mirror
 help / color / mirror / Atom feed
From: Andrew Bresticker <>
To: Palmer Dabbelt <>
Cc: Paul Walmsley <>,
	Celeste Liu <>,
	dram <>, Ruizhe Pan <>,,,,
	Andrew Bresticker <>
Subject: [PATCH v4 0/2] Make mmap() with PROT_WRITE imply PROT_READ
Date: Thu, 15 Sep 2022 15:37:00 -0400	[thread overview]
Message-ID: <> (raw)

Commit 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is
invalid") made mmap() reject mappings with only PROT_WRITE set in an
attempt to fix an observed inconsistency in behavior when attempting
to read from a PROT_WRITE-only mapping. The root cause of this behavior
was actually that while RISC-V's protection_map maps VM_WRITE to
readable PTE permissions (since write-only PTEs are considered reserved
by the privileged spec), the page fault handler considered loads from
VM_WRITE-only VMAs illegal accesses. Fix the underlying cause by
handling faults in VM_WRITE-only VMAs (patch 1) and then re-enable
use of mmap(PROT_WRITE) (patch 2), making RISC-V's behavior consistent
with all other architectures that don't support write-only PTEs.

Both patches are tagged as fixes for the aforementioned commit since that
commit made a userspace visible change that will break any software relying
on mmap(PROT_WRITE). (Also cc: stable since the offending commit was
itself backported to stable).

v1 -> v2: Allow handling of load faults in VM_WRITE VMAs
v2 -> v3: Split into two pathces
v3 -> v4: Fixes tags (+ this cover letter)

Andrew Bresticker (2):
  riscv: Make VM_WRITE imply VM_READ
  riscv: Allow PROT_WRITE-only mmap()

 arch/riscv/kernel/sys_riscv.c | 3 ---
 arch/riscv/mm/fault.c         | 3 ++-
 2 files changed, 2 insertions(+), 4 deletions(-)


linux-riscv mailing list

             reply	other threads:[~2022-09-15 19:37 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-15 19:37 Andrew Bresticker [this message]
2022-09-15 19:37 ` [PATCH v4 1/2] riscv: Make VM_WRITE imply VM_READ Andrew Bresticker
2022-09-15 19:37 ` [PATCH v4 2/2] riscv: Allow PROT_WRITE-only mmap() Andrew Bresticker
2022-10-11 17:04 ` [PATCH v4 0/2] Make mmap() with PROT_WRITE imply PROT_READ Conor Dooley
2022-10-13 21:01 ` Palmer Dabbelt

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).