From e873c74132f0c5f1452816cd9bb26208f0bba1e1 Mon Sep 17 00:00:00 2001
From: Shivank Garg <shivankg@amd.com>
Date: Sat, 22 Aug 2026 19:22:05 +0000
Subject: dmaengine: fix use-after-free in dma_chan_put() and
 dma_release_channel()

When dma_device_put() drops the last reference on chan->device->ref,
dma_device_release() runs and may free the dma_device along with its
channels.

dma_chan_put() then still reads chan->device->owner via
dma_chan_to_owner() for the trailing module_put(). KASAN catches it:

	slab-use-after-free in dma_chan_put+0x3e6/0x4c0
	Read of size 8 by task insmod/6319
	Freed by task 6319:
	  kfree+0x225/0x470
	  dma_chan_put+0x395/0x4c0
	  dmaengine_put+0xf8/0x160

Cache the module owner in dma_chan_put() before the put so the trailing
module_put() does not need chan->device.

Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct")
Suggested-by: Sashiko <sashiko-bot@kernel.org>
Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Shivank Garg <shivankg@amd.com>
Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
---
 drivers/video/fbdev/maxinefb.c | 175 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 175 insertions(+)
 create mode 100644 drivers/video/fbdev/maxinefb.c

(limited to 'drivers/video/fbdev/maxinefb.c')

diff --git a/drivers/video/fbdev/maxinefb.c b/drivers/video/fbdev/maxinefb.c
new file mode 100644
index 000000000..67d4bd881
--- /dev/null
+++ b/drivers/video/fbdev/maxinefb.c
@@ -0,0 +1,175 @@
+/*
+ *      linux/drivers/video/maxinefb.c
+ *
+ *	DECstation 5000/xx onboard framebuffer support ... derived from:
+ *	"HP300 Topcat framebuffer support (derived from macfb of all things)
+ *	Phil Blundell <philb@gnu.org> 1998", the original code can be
+ *      found in the file hpfb.c in the same directory.
+ *
+ *      DECstation related code Copyright (C) 1999,2000,2001 by
+ *      Michael Engel <engel@unix-ag.org> and
+ *      Karsten Merker <merker@linuxtag.org>.
+ *      This file is subject to the terms and conditions of the GNU General
+ *      Public License.  See the file COPYING in the main directory of this
+ *      archive for more details.
+ *
+ */
+
+/*
+ * Changes:
+ * 2001/01/27 removed debugging and testing code, fixed fb_ops
+ *            initialization which had caused a crash before,
+ *            general cleanup, first official release (KM)
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/fb.h>
+#include <video/maxinefb.h>
+
+/* bootinfo.h defines the machine type values, needed when checking */
+/* whether are really running on a maxine, KM                       */
+#include <asm/bootinfo.h>
+
+static struct fb_info fb_info;
+
+static const struct fb_var_screeninfo maxinefb_defined = {
+	.xres =		1024,
+	.yres =		768,
+	.xres_virtual =	1024,
+	.yres_virtual =	768,
+	.bits_per_pixel =8,
+	.activate =	FB_ACTIVATE_NOW,
+	.height =	-1,
+	.width =	-1,
+	.vmode =	FB_VMODE_NONINTERLACED,
+};
+
+static struct fb_fix_screeninfo maxinefb_fix __initdata = {
+	.id =		"Maxine",
+	.smem_len =	(1024*768),
+	.type =		FB_TYPE_PACKED_PIXELS,
+	.visual =	FB_VISUAL_PSEUDOCOLOR,
+	.line_length =	1024,
+};
+
+/* Handle the funny Inmos RamDAC/video controller ... */
+
+static void maxinefb_ims332_write_register(int regno, register unsigned int val)
+{
+	register unsigned char *regs = (char *) MAXINEFB_IMS332_ADDRESS;
+	unsigned char *wptr;
+
+	wptr = regs + 0xa0000 + (regno << 4);
+	*((volatile unsigned int *) (regs)) = (val >> 8) & 0xff00;
+	*((volatile unsigned short *) (wptr)) = val;
+}
+
+#if 0
+/* dead code: leave here for hardware interface documentation */
+static unsigned int maxinefb_ims332_read_register(int regno)
+{
+	register unsigned char *regs = (char *) MAXINEFB_IMS332_ADDRESS;
+	unsigned char *rptr;
+	register unsigned int j, k;
+
+	rptr = regs + 0x80000 + (regno << 4);
+	j = *((volatile unsigned short *) rptr);
+	k = *((volatile unsigned short *) regs);
+
+	return (j & 0xffff) | ((k & 0xff00) << 8);
+}
+#endif
+
+/* Set the palette */
+static int maxinefb_setcolreg(unsigned regno, unsigned red, unsigned green,
+			      unsigned blue, unsigned transp, struct fb_info *info)
+{
+	/* value to be written into the palette reg. */
+	unsigned long hw_colorvalue = 0;
+
+	if (regno > 255)
+		return 1;
+
+	red   >>= 8;    /* The cmap fields are 16 bits    */
+	green >>= 8;    /* wide, but the harware colormap */
+	blue  >>= 8;    /* registers are only 8 bits wide */
+
+	hw_colorvalue = (blue << 16) + (green << 8) + (red);
+
+	maxinefb_ims332_write_register(IMS332_REG_COLOR_PALETTE + regno,
+				       hw_colorvalue);
+	return 0;
+}
+
+static const struct fb_ops maxinefb_ops = {
+	.owner		= THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_setcolreg	= maxinefb_setcolreg,
+};
+
+static int __init maxinefb_init(void)
+{
+	unsigned long fboff;
+	unsigned long fb_start;
+	int i;
+
+	if (fb_get_options("maxinefb", NULL))
+		return -ENODEV;
+
+	/* Validate we're on the proper machine type */
+	if (mips_machtype != MACH_DS5000_XX) {
+		return -EINVAL;
+	}
+
+	printk(KERN_INFO "Maxinefb: Personal DECstation detected\n");
+	printk(KERN_INFO "Maxinefb: initializing onboard framebuffer\n");
+
+	/* Framebuffer display memory base address */
+	fb_start = DS5000_xx_ONBOARD_FBMEM_START;
+
+	/* Clear screen */
+	for (fboff = fb_start; fboff < fb_start + 0x1ffff; fboff++)
+		*(volatile unsigned char *)fboff = 0x0;
+
+	maxinefb_fix.smem_start = fb_start;
+
+	/* erase hardware cursor */
+	for (i = 0; i < 512; i++) {
+		maxinefb_ims332_write_register(IMS332_REG_CURSOR_RAM + i,
+					       0);
+		/*
+		   if (i&0x8 == 0)
+		   maxinefb_ims332_write_register (IMS332_REG_CURSOR_RAM + i, 0x0f);
+		   else
+		   maxinefb_ims332_write_register (IMS332_REG_CURSOR_RAM + i, 0xf0);
+		 */
+	}
+
+	fb_info.fbops = &maxinefb_ops;
+	fb_info.screen_base = (char *)maxinefb_fix.smem_start;
+	fb_info.var = maxinefb_defined;
+	fb_info.fix = maxinefb_fix;
+
+	fb_alloc_cmap(&fb_info.cmap, 256, 0);
+
+	if (register_framebuffer(&fb_info) < 0)
+		return -ENODEV;
+	return 0;
+}
+
+static void __exit maxinefb_exit(void)
+{
+	unregister_framebuffer(&fb_info);
+}
+
+module_init(maxinefb_init);
+module_exit(maxinefb_exit);
+
+MODULE_LICENSE("GPL");
-- 
cgit v1.3.1