public inbox for [email protected]
 help / color / mirror / Atom feed
From: "Fabio M. De Francesco" <[email protected]>
To: Benjamin LaHaise <[email protected]>,
	Alexander Viro <[email protected]>,
	Eric Biederman <[email protected]>,
	Kees Cook <[email protected]>,
	Dan Williams <[email protected]>,
	Matthew Wilcox <[email protected]>, Jan Kara <[email protected]>,
	Jeff Layton <[email protected]>,
	Chuck Lever <[email protected]>,
	Jens Axboe <[email protected]>,
	Pavel Begunkov <[email protected]>,
	Thomas Gleixner <[email protected]>,
	Paul Walmsley <[email protected]>,
	Palmer Dabbelt <[email protected]>,
	Albert Ou <[email protected]>,
	Nathan Chancellor <[email protected]>,
	Nick Desaulniers <[email protected]>,
	Tom Rix <[email protected]>,
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected]
Cc: "Fabio M. De Francesco" <[email protected]>,
	Ira Weiny <[email protected]>
Subject: [PATCH] fs: Call kmap_local_page() in copy_string_kernel()
Date: Sun, 10 Jul 2022 12:01:36 +0200	[thread overview]
Message-ID: <[email protected]> (raw)

The use of kmap_atomic() is being deprecated in favor of kmap_local_page().

With kmap_local_page(), the mappings are per thread, CPU local, not
globally visible and can take page faults. Furthermore, the mappings can be
acquired from any context (including interrupts).

Therefore, use kmap_local_page() in copy_string_kernel() instead of
kmap_atomic().

Tested with xfstests on a QEMU + KVM 32-bits VM booting a kernel with
HIGHMEM64GB enabled.

Suggested-by: Ira Weiny <[email protected]>
Signed-off-by: Fabio M. De Francesco <[email protected]>
---

I sent a first patch to fs/exec.c for converting kmap() and kmap_atomic()
to kmap_local_page():
https://lore.kernel.org/lkml/[email protected]/

Some days ago, Ira Weiny, while he was reviewing that patch, made me notice
that I had overlooked a second kmap_atomic() in the same file (thanks):
https://lore.kernel.org/lkml/YsiQptk19txHrG4c@iweiny-desk3/

I've been asked to send this as an additional change. This is why there will
not be any second version of that previous patch.

 fs/exec.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 4a2129c0d422..5fa652ca5823 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -639,11 +639,11 @@ int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
 		page = get_arg_page(bprm, pos, 1);
 		if (!page)
 			return -E2BIG;
-		kaddr = kmap_atomic(page);
+		kaddr = kmap_local_page(page);
 		flush_arg_page(bprm, pos & PAGE_MASK, page);
 		memcpy(kaddr + offset_in_page(pos), arg, bytes_to_copy);
 		flush_dcache_page(page);
-		kunmap_atomic(kaddr);
+		kunmap_local(kaddr);
 		put_arg_page(page);
 	}
 
-- 
2.36.1


             reply	other threads:[~2022-07-10 10:01 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-10 10:01 Fabio M. De Francesco [this message]
2022-07-22  0:14 ` [PATCH] fs: Call kmap_local_page() in copy_string_kernel() Ira Weiny
2022-07-23  1:02   ` Fabio M. De Francesco

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:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

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

  git send-email \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* 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