linux-kernel - [PATCH] usb: core: do not allocate buffers from a DMA zone unnecessarily

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20250320154733.392410-1-ptesarik@suse.com>
Date: Thu, 20 Mar 2025 16:47:33 +0100
From: Petr Tesarik <ptesarik@...e.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Petr Tesarik <ptesarik@...e.com>
Subject: [PATCH] usb: core: do not allocate buffers from a DMA zone unnecessarily

There is no reason to keep GFP zone modifiers in hcd_buffer_alloc():
- PIO mode can use any kernel-addressable memory
- dma_alloc_coherent() ignores memory zone bits

The only place where GFP zone bits are used is when dma_pool_alloc() needs
to allocate a new struct dma_page, but that is an omission rather than
intention.

Signed-off-by: Petr Tesarik <ptesarik@...e.com>
---
 drivers/usb/core/buffer.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/core/buffer.c b/drivers/usb/core/buffer.c
index 87230869e1fa..2be4c2a5b214 100644
--- a/drivers/usb/core/buffer.c
+++ b/drivers/usb/core/buffer.c
@@ -108,10 +108,6 @@ void hcd_buffer_destroy(struct usb_hcd *hcd)
 }
 
 
-/* sometimes alloc/free could use kmalloc with GFP_DMA, for
- * better sharing and to leverage mm/slab.c intelligence.
- */
-
 void *hcd_buffer_alloc(
 	struct usb_bus		*bus,
 	size_t			size,
@@ -128,6 +124,9 @@ void *hcd_buffer_alloc(
 	if (hcd->localmem_pool)
 		return gen_pool_dma_alloc(hcd->localmem_pool, size, dma);
 
+	/* DMA API ignores zone modifiers, and PIO should go with default */
+	mem_flags &= ~GFP_ZONEMASK;
+
 	/* some USB hosts just use PIO */
 	if (!hcd_uses_dma(hcd)) {
 		*dma = ~(dma_addr_t) 0;
-- 
2.48.1