linux-kernel - [PATCH] media: vb2: frame_vector.c: replace WARN

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-next>] [day] [month] [year] [list]

Message-ID: <d5e1ee76-75b3-26cb-23ae-cf6ab40597b7@xs4all.nl>
Date:   Thu, 17 Aug 2023 12:41:32 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Linux Media Mailing List <linux-media@...r.kernel.org>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Jan Kara <jack@...e.cz>, David Hildenbrand <david@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH] media: vb2: frame_vector.c: replace WARN_ONCE with a comment

The WARN_ONCE was issued also in cases that had nothing to do with VM_IO
(e.g. if the start address was just a random value and uaccess fails with
-EFAULT).

There are no reports of WARN_ONCE being issued for actual VM_IO cases, so
just drop it and instead add a note to the comment before the function.

Signed-off-by: Hans Verkuil <hverkuil-cisco@...all.nl>
---
diff --git a/drivers/media/common/videobuf2/frame_vector.c b/drivers/media/common/videobuf2/frame_vector.c
index 0f430ddc1f67..fd87747be9b1 100644
--- a/drivers/media/common/videobuf2/frame_vector.c
+++ b/drivers/media/common/videobuf2/frame_vector.c
@@ -31,6 +31,10 @@
  * different type underlying the specified range of virtual addresses.
  * When the function isn't able to map a single page, it returns error.
  *
+ * Note that get_vaddr_frames() cannot follow VM_IO mappings. It used
+ * to be able to do that, but that could (racily) return non-refcounted
+ * pfns.
+ *
  * This function takes care of grabbing mmap_lock as necessary.
  */
 int get_vaddr_frames(unsigned long start, unsigned int nr_frames, bool write,
@@ -59,8 +63,6 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, bool write,
 	if (likely(ret > 0))
 		return ret;

-	/* This used to (racily) return non-refcounted pfns. Let people know */
-	WARN_ONCE(1, "get_vaddr_frames() cannot follow VM_IO mapping");
 	vec->nr_frames = 0;
 	return ret ? ret : -EFAULT;
 }