Re: [PATCH] fs/proc/kcore: reinstate bounce buffer for KCORE_TEXT regions

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Hm good point, actually, now we're using the bounce buffer we don't need to
avoid usermode hardening any more.

However since we've established a bounce buffer ourselves its still
appropriate to use _copy_to_iter() as we know the source region is good to
copy from.

To make life easy I'll just respin with an updated comment :)

I'm not too picky this time, no need to resend if everybody else is fine :P


Haha you know the classic Lorenzo respin spiral and want to avoid it I see ;)

Don't want to make your apparently stressful week more stressful. Not this time ;)


The comment is actually inaccurate now, so to avoid noise + make life easy
(maybe) for Andrew here's a fix patch that just corrects the comment:-

----8<----

 From d2b8fb271f21b79048e5630699133f77a93d0481 Mon Sep 17 00:00:00 2001
From: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Date: Tue, 1 Aug 2023 17:36:08 +0100
Subject: [PATCH] fs/proc/kcore: correct comment

Correct comment to be strictly correct about reasoning.

Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
---
  fs/proc/kcore.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 3bc689038232..23fc24d16b31 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -568,8 +568,8 @@ static ssize_t read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter)
  					goto out;
  				}
  			/*
-			 * We use _copy_to_iter() to bypass usermode hardening
-			 * which would otherwise prevent this operation.
+			 * We know the bounce buffer is safe to copy from, so
+			 * use _copy_to_iter() directly.
  			 */
  			} else if (_copy_to_iter(buf, tsz, iter) != tsz) {
  				ret = -EFAULT;
--
2.41.0


Thanks!

Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers,

David / dhildenb




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