linux-kernel - [PATCH v2 1/3] binder: Use memset_page() in binder_alloc_clear

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20220425175754.8180-2-fmdefrancesco@gmail.com>
Date:   Mon, 25 Apr 2022 19:57:52 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Christian Brauner <brauner@...nel.org>,
        Hridya Valsaraju <hridya@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Ira Weiny <ira.weiny@...el.com>, linux-kernel@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Todd Kjos <tkjos@...gle.com>
Subject: [PATCH v2 1/3] binder: Use memset_page() in binder_alloc_clear_buf()

The use of kmap() is being deprecated in favor of kmap_local_page()
where it is feasible. With kmap_local_page(), the mapping is per
thread, CPU local and not globally visible.

binder_alloc_clear_buf() is a function where the use of kmap_local_page()
in place of kmap() is correctly suited because the mapping is local to the
thread.

Therefore, use kmap_local_page() / kunmap_local() but, instead of open
coding these two functions and adding a memset() of the virtual address
of the mapping, prefer memset_page().

Cc: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Acked-by: Todd Kjos <tkjos@...gle.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
---

v1->v2: Add Todd Kjos's tag in the commit message (thanks!)

 drivers/android/binder_alloc.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 2ac1008a5f39..0b3f2f569053 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -1175,14 +1175,11 @@ static void binder_alloc_clear_buf(struct binder_alloc *alloc,
 		unsigned long size;
 		struct page *page;
 		pgoff_t pgoff;
-		void *kptr;
 
 		page = binder_alloc_get_page(alloc, buffer,
 					     buffer_offset, &pgoff);
 		size = min_t(size_t, bytes, PAGE_SIZE - pgoff);
-		kptr = kmap(page) + pgoff;
-		memset(kptr, 0, size);
-		kunmap(page);
+		memset_page(page, pgoff, 0, size);
 		bytes -= size;
 		buffer_offset += size;
 	}
-- 
2.34.1