Hi,
thanks for backporting.
You also have to remove the calls to vga_switcheroo_client_fb_set() from
these files
https://elixir.bootlin.com/linux/v6.6/source/drivers/gpu/drm/i915/display/intel_fbdev.c
https://elixir.bootlin.com/linux/v6.6/source/drivers/gpu/drm/radeon/radeon_fbdev.c
Best regards
Thomas
Am 01.12.25 um 23:51 schrieb Sasha Levin:
From: Thomas Zimmermann <[email protected]>
[ Upstream commit eb76d0f5553575599561010f24c277cc5b31d003 ]
Protect vga_switcheroo_client_fb_set() with console lock. Avoids OOB
access in fbcon_remap_all(). Without holding the console lock the call
races with switching outputs.
VGA switcheroo calls fbcon_remap_all() when switching clients. The fbcon
function uses struct fb_info.node, which is set by register_framebuffer().
As the fb-helper code currently sets up VGA switcheroo before registering
the framebuffer, the value of node is -1 and therefore not a legal value.
For example, fbcon uses the value within set_con2fb_map() [1] as an index
into an array.
Moving vga_switcheroo_client_fb_set() after register_framebuffer() can
result in VGA switching that does not switch fbcon correctly.
Therefore move vga_switcheroo_client_fb_set() under fbcon_fb_registered(),
which already holds the console lock. Fbdev calls fbcon_fb_registered()
from within register_framebuffer(). Serializes the helper with VGA
switcheroo's call to fbcon_remap_all().
Although vga_switcheroo_client_fb_set() takes an instance of struct fb_info
as parameter, it really only needs the contained fbcon state. Moving the
call to fbcon initialization is therefore cleaner than before. Only amdgpu,
i915, nouveau and radeon support vga_switcheroo. For all other drivers,
this change does nothing.
Signed-off-by: Thomas Zimmermann <[email protected]>
Link:
https://elixir.bootlin.com/linux/v6.17/source/drivers/video/fbdev/core/fbcon.c#L2942
# [1]
Fixes: 6a9ee8af344e ("vga_switcheroo: initial implementation (v15)")
Acked-by: Javier Martinez Canillas <[email protected]>
Acked-by: Alex Deucher <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: <[email protected]> # v2.6.34+
Link: https://patch.msgid.link/[email protected]
[ drm_fb_helper_unregister_info() lacks vga_switcheroo code ]
Signed-off-by: Sasha Levin <[email protected]>
---
drivers/gpu/drm/drm_fb_helper.c | 7 -------
drivers/video/fbdev/core/fbcon.c | 9 +++++++++
2 files changed, 9 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index b507c1c008a3e..3891837a78414 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -30,9 +30,7 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/console.h>
-#include <linux/pci.h>
#include <linux/sysrq.h>
-#include <linux/vga_switcheroo.h>
#include <drm/drm_atomic.h>
#include <drm/drm_drv.h>
@@ -1668,7 +1666,6 @@ static int drm_fb_helper_find_sizes(struct drm_fb_helper
*fb_helper,
static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
{
struct drm_client_dev *client = &fb_helper->client;
- struct drm_device *dev = fb_helper->dev;
struct drm_fb_helper_surface_size sizes;
int ret;
@@ -1687,10 +1684,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
strcpy(fb_helper->fb->comm, "[fbcon]");
- /* Set the fb info for vgaswitcheroo clients. Does nothing otherwise. */
- if (dev_is_pci(dev->dev))
- vga_switcheroo_client_fb_set(to_pci_dev(dev->dev),
fb_helper->info);
-
return 0;
}
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 78a5b22c8d150..8b2c3065c0c26 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -64,6 +64,7 @@
#include <linux/console.h>
#include <linux/string.h>
#include <linux/kd.h>
+#include <linux/pci.h>
#include <linux/slab.h>
#include <linux/fb.h>
#include <linux/fbcon.h>
@@ -75,6 +76,7 @@
#include <linux/interrupt.h>
#include <linux/crc32.h> /* For counting font checksums */
#include <linux/uaccess.h>
+#include <linux/vga_switcheroo.h>
#include <asm/irq.h>
#include "fbcon.h"
@@ -2913,6 +2915,9 @@ void fbcon_fb_unregistered(struct fb_info *info)
console_lock();
+ if (info->device && dev_is_pci(info->device))
+ vga_switcheroo_client_fb_set(to_pci_dev(info->device), NULL);
+
fbcon_registered_fb[info->node] = NULL;
fbcon_num_registered_fb--;
@@ -3046,6 +3051,10 @@ static int do_fb_registered(struct fb_info *info)
}
}
+ /* Set the fb info for vga_switcheroo clients. Does nothing otherwise. */
+ if (info->device && dev_is_pci(info->device))
+ vga_switcheroo_client_fb_set(to_pci_dev(info->device), info);
+
return ret;
}
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)
