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
next 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
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