drivers/video/fbdev/simplefb.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-)
The pm_domain cleanup can not be devres managed as it uses struct
simplefb_par which is allocated within struct fb_info by
framebuffer_alloc(). This allocation is explicitly freed by
unregister_framebuffer() in simplefb_remove().
Devres managed cleanup runs after the device remove call and thus can no
longer access struct simplefb_par.
Call simplefb_detach_genpds() explicitly from simplefb_destroy() like
the cleanup functions for clocks and regulators.
Fixes an use after free on M2 Mac mini during
aperture_remove_conflicting_devices() using the downstream asahi kernel
with Debian's kernel config. For unknown reasons this started to
consistently dereference an invalid pointer in v6.16.3 based kernels.
[ 6.736134] BUG: KASAN: slab-use-after-free in simplefb_detach_genpds+0x58/0x220
[ 6.743545] Read of size 4 at addr ffff8000304743f0 by task (udev-worker)/227
[ 6.750697]
[ 6.752182] CPU: 6 UID: 0 PID: 227 Comm: (udev-worker) Tainted: G S 6.16.3-asahi+ #16 PREEMPTLAZY
[ 6.752186] Tainted: [S]=CPU_OUT_OF_SPEC
[ 6.752187] Hardware name: Apple Mac mini (M2, 2023) (DT)
[ 6.752189] Call trace:
[ 6.752190] show_stack+0x34/0x98 (C)
[ 6.752194] dump_stack_lvl+0x60/0x80
[ 6.752197] print_report+0x17c/0x4d8
[ 6.752201] kasan_report+0xb4/0x100
[ 6.752206] __asan_report_load4_noabort+0x20/0x30
[ 6.752209] simplefb_detach_genpds+0x58/0x220
[ 6.752213] devm_action_release+0x50/0x98
[ 6.752216] release_nodes+0xd0/0x2c8
[ 6.752219] devres_release_all+0xfc/0x178
[ 6.752221] device_unbind_cleanup+0x28/0x168
[ 6.752224] device_release_driver_internal+0x34c/0x470
[ 6.752228] device_release_driver+0x20/0x38
[ 6.752231] bus_remove_device+0x1b0/0x380
[ 6.752234] device_del+0x314/0x820
[ 6.752238] platform_device_del+0x3c/0x1e8
[ 6.752242] platform_device_unregister+0x20/0x50
[ 6.752246] aperture_detach_platform_device+0x1c/0x30
[ 6.752250] aperture_detach_devices+0x16c/0x290
[ 6.752253] aperture_remove_conflicting_devices+0x34/0x50
...
[ 6.752343]
[ 6.967409] Allocated by task 62:
[ 6.970724] kasan_save_stack+0x3c/0x70
[ 6.974560] kasan_save_track+0x20/0x40
[ 6.978397] kasan_save_alloc_info+0x40/0x58
[ 6.982670] __kasan_kmalloc+0xd4/0xd8
[ 6.986420] __kmalloc_noprof+0x194/0x540
[ 6.990432] framebuffer_alloc+0xc8/0x130
[ 6.994444] simplefb_probe+0x258/0x2378
...
[ 7.054356]
[ 7.055838] Freed by task 227:
[ 7.058891] kasan_save_stack+0x3c/0x70
[ 7.062727] kasan_save_track+0x20/0x40
[ 7.066565] kasan_save_free_info+0x4c/0x80
[ 7.070751] __kasan_slab_free+0x6c/0xa0
[ 7.074675] kfree+0x10c/0x380
[ 7.077727] framebuffer_release+0x5c/0x90
[ 7.081826] simplefb_destroy+0x1b4/0x2c0
[ 7.085837] put_fb_info+0x98/0x100
[ 7.089326] unregister_framebuffer+0x178/0x320
[ 7.093861] simplefb_remove+0x3c/0x60
[ 7.097611] platform_remove+0x60/0x98
[ 7.101361] device_remove+0xb8/0x160
[ 7.105024] device_release_driver_internal+0x2fc/0x470
[ 7.110256] device_release_driver+0x20/0x38
[ 7.114529] bus_remove_device+0x1b0/0x380
[ 7.118628] device_del+0x314/0x820
[ 7.122116] platform_device_del+0x3c/0x1e8
[ 7.126302] platform_device_unregister+0x20/0x50
[ 7.131012] aperture_detach_platform_device+0x1c/0x30
[ 7.136157] aperture_detach_devices+0x16c/0x290
[ 7.140779] aperture_remove_conflicting_devices+0x34/0x50
...
Reported-by: Daniel Huhardeaux <tech@tootai.net>
Cc: stable@vger.kernel.org
Fixes: 92a511a568e44 ("fbdev/simplefb: Add support for generic power-domains")
Signed-off-by: Janne Grunau <j@jannau.net>
---
Changes in v3:
- release power-domains on probe errors
- set par->num_genpds when it's <= 1
- set par->num_genpds to 0 after detaching
- Link to v2: https://lore.kernel.org/r/20250908-simplefb-genpd-uaf-v2-1-f88a0d9d880f@jannau.net
Changes in v2:
- reworked change due to missed use of `par->num_genpds` before setting
it. Missed in testing due to mixing up FB_SIMPLE and SYSFB_SIMPLEFB.
- Link to v1: https://lore.kernel.org/r/20250901-simplefb-genpd-uaf-v1-1-0d9f3a34c4dc@jannau.net
---
drivers/video/fbdev/simplefb.c | 31 +++++++++++++++++++++++--------
1 file changed, 23 insertions(+), 8 deletions(-)
diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c
index 1893815dc67f4c1403eea42c0e10a7ead4d96ba9..6acf5a00c2bacfab89c3a63bab3d8b1b091a20a8 100644
--- a/drivers/video/fbdev/simplefb.c
+++ b/drivers/video/fbdev/simplefb.c
@@ -93,6 +93,7 @@ struct simplefb_par {
static void simplefb_clocks_destroy(struct simplefb_par *par);
static void simplefb_regulators_destroy(struct simplefb_par *par);
+static void simplefb_detach_genpds(void *res);
/*
* fb_ops.fb_destroy is called by the last put_fb_info() call at the end
@@ -105,6 +106,7 @@ static void simplefb_destroy(struct fb_info *info)
simplefb_regulators_destroy(info->par);
simplefb_clocks_destroy(info->par);
+ simplefb_detach_genpds(info->par);
if (info->screen_base)
iounmap(info->screen_base);
@@ -445,13 +447,14 @@ static void simplefb_detach_genpds(void *res)
if (!IS_ERR_OR_NULL(par->genpds[i]))
dev_pm_domain_detach(par->genpds[i], true);
}
+ par->num_genpds = 0;
}
static int simplefb_attach_genpds(struct simplefb_par *par,
struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
- unsigned int i;
+ unsigned int i, num_genpds;
int err;
err = of_count_phandle_with_args(dev->of_node, "power-domains",
@@ -465,26 +468,35 @@ static int simplefb_attach_genpds(struct simplefb_par *par,
return err;
}
- par->num_genpds = err;
+ num_genpds = err;
/*
* Single power-domain devices are handled by the driver core, so
* nothing to do here.
*/
- if (par->num_genpds <= 1)
+ if (num_genpds <= 1) {
+ par->num_genpds = num_genpds;
return 0;
+ }
- par->genpds = devm_kcalloc(dev, par->num_genpds, sizeof(*par->genpds),
+ par->genpds = devm_kcalloc(dev, num_genpds, sizeof(*par->genpds),
GFP_KERNEL);
if (!par->genpds)
return -ENOMEM;
- par->genpd_links = devm_kcalloc(dev, par->num_genpds,
+ par->genpd_links = devm_kcalloc(dev, num_genpds,
sizeof(*par->genpd_links),
GFP_KERNEL);
if (!par->genpd_links)
return -ENOMEM;
+ /*
+ * Set par->num_genpds only after genpds and genpd_links are allocated
+ * to exit early from simplefb_detach_genpds() without full
+ * initialisation.
+ */
+ par->num_genpds = num_genpds;
+
for (i = 0; i < par->num_genpds; i++) {
par->genpds[i] = dev_pm_domain_attach_by_id(dev, i);
if (IS_ERR(par->genpds[i])) {
@@ -506,9 +518,10 @@ static int simplefb_attach_genpds(struct simplefb_par *par,
dev_warn(dev, "failed to link power-domain %u\n", i);
}
- return devm_add_action_or_reset(dev, simplefb_detach_genpds, par);
+ return 0;
}
#else
+static void simplefb_detach_genpds(void *res) { }
static int simplefb_attach_genpds(struct simplefb_par *par,
struct platform_device *pdev)
{
@@ -622,18 +635,20 @@ static int simplefb_probe(struct platform_device *pdev)
ret = devm_aperture_acquire_for_platform_device(pdev, par->base, par->size);
if (ret) {
dev_err(&pdev->dev, "Unable to acquire aperture: %d\n", ret);
- goto error_regulators;
+ goto error_genpds;
}
ret = register_framebuffer(info);
if (ret < 0) {
dev_err(&pdev->dev, "Unable to register simplefb: %d\n", ret);
- goto error_regulators;
+ goto error_genpds;
}
dev_info(&pdev->dev, "fb%d: simplefb registered!\n", info->node);
return 0;
+error_genpds:
+ simplefb_detach_genpds(par);
error_regulators:
simplefb_regulators_destroy(par);
error_clocks:
---
base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
change-id: 20250901-simplefb-genpd-uaf-352704761a29
Best regards,
--
Janne Grunau <j@jannau.net>On 9/15/25 08:36, Janne Grunau wrote:
> The pm_domain cleanup can not be devres managed as it uses struct
> simplefb_par which is allocated within struct fb_info by
> framebuffer_alloc(). This allocation is explicitly freed by
> unregister_framebuffer() in simplefb_remove().
> Devres managed cleanup runs after the device remove call and thus can no
> longer access struct simplefb_par.
> Call simplefb_detach_genpds() explicitly from simplefb_destroy() like
> the cleanup functions for clocks and regulators.
>
> Fixes an use after free on M2 Mac mini during
> aperture_remove_conflicting_devices() using the downstream asahi kernel
> with Debian's kernel config. For unknown reasons this started to
> consistently dereference an invalid pointer in v6.16.3 based kernels.
>
> [ 6.736134] BUG: KASAN: slab-use-after-free in simplefb_detach_genpds+0x58/0x220
> [ 6.743545] Read of size 4 at addr ffff8000304743f0 by task (udev-worker)/227
> [ 6.750697]
> [ 6.752182] CPU: 6 UID: 0 PID: 227 Comm: (udev-worker) Tainted: G S 6.16.3-asahi+ #16 PREEMPTLAZY
> [ 6.752186] Tainted: [S]=CPU_OUT_OF_SPEC
> [ 6.752187] Hardware name: Apple Mac mini (M2, 2023) (DT)
> [ 6.752189] Call trace:
> [ 6.752190] show_stack+0x34/0x98 (C)
> [ 6.752194] dump_stack_lvl+0x60/0x80
> [ 6.752197] print_report+0x17c/0x4d8
> [ 6.752201] kasan_report+0xb4/0x100
> [ 6.752206] __asan_report_load4_noabort+0x20/0x30
> [ 6.752209] simplefb_detach_genpds+0x58/0x220
> [ 6.752213] devm_action_release+0x50/0x98
> [ 6.752216] release_nodes+0xd0/0x2c8
> [ 6.752219] devres_release_all+0xfc/0x178
> [ 6.752221] device_unbind_cleanup+0x28/0x168
> [ 6.752224] device_release_driver_internal+0x34c/0x470
> [ 6.752228] device_release_driver+0x20/0x38
> [ 6.752231] bus_remove_device+0x1b0/0x380
> [ 6.752234] device_del+0x314/0x820
> [ 6.752238] platform_device_del+0x3c/0x1e8
> [ 6.752242] platform_device_unregister+0x20/0x50
> [ 6.752246] aperture_detach_platform_device+0x1c/0x30
> [ 6.752250] aperture_detach_devices+0x16c/0x290
> [ 6.752253] aperture_remove_conflicting_devices+0x34/0x50
> ...
> [ 6.752343]
> [ 6.967409] Allocated by task 62:
> [ 6.970724] kasan_save_stack+0x3c/0x70
> [ 6.974560] kasan_save_track+0x20/0x40
> [ 6.978397] kasan_save_alloc_info+0x40/0x58
> [ 6.982670] __kasan_kmalloc+0xd4/0xd8
> [ 6.986420] __kmalloc_noprof+0x194/0x540
> [ 6.990432] framebuffer_alloc+0xc8/0x130
> [ 6.994444] simplefb_probe+0x258/0x2378
> ...
> [ 7.054356]
> [ 7.055838] Freed by task 227:
> [ 7.058891] kasan_save_stack+0x3c/0x70
> [ 7.062727] kasan_save_track+0x20/0x40
> [ 7.066565] kasan_save_free_info+0x4c/0x80
> [ 7.070751] __kasan_slab_free+0x6c/0xa0
> [ 7.074675] kfree+0x10c/0x380
> [ 7.077727] framebuffer_release+0x5c/0x90
> [ 7.081826] simplefb_destroy+0x1b4/0x2c0
> [ 7.085837] put_fb_info+0x98/0x100
> [ 7.089326] unregister_framebuffer+0x178/0x320
> [ 7.093861] simplefb_remove+0x3c/0x60
> [ 7.097611] platform_remove+0x60/0x98
> [ 7.101361] device_remove+0xb8/0x160
> [ 7.105024] device_release_driver_internal+0x2fc/0x470
> [ 7.110256] device_release_driver+0x20/0x38
> [ 7.114529] bus_remove_device+0x1b0/0x380
> [ 7.118628] device_del+0x314/0x820
> [ 7.122116] platform_device_del+0x3c/0x1e8
> [ 7.126302] platform_device_unregister+0x20/0x50
> [ 7.131012] aperture_detach_platform_device+0x1c/0x30
> [ 7.136157] aperture_detach_devices+0x16c/0x290
> [ 7.140779] aperture_remove_conflicting_devices+0x34/0x50
> ...
>
> Reported-by: Daniel Huhardeaux <tech@tootai.net>
> Cc: stable@vger.kernel.org
> Fixes: 92a511a568e44 ("fbdev/simplefb: Add support for generic power-domains")
> Signed-off-by: Janne Grunau <j@jannau.net>
> ---
> Changes in v3:
> - release power-domains on probe errors
> - set par->num_genpds when it's <= 1
> - set par->num_genpds to 0 after detaching
> - Link to v2: https://lore.kernel.org/r/20250908-simplefb-genpd-uaf-v2-1-f88a0d9d880f@jannau.net
>
> Changes in v2:
> - reworked change due to missed use of `par->num_genpds` before setting
> it. Missed in testing due to mixing up FB_SIMPLE and SYSFB_SIMPLEFB.
> - Link to v1: https://lore.kernel.org/r/20250901-simplefb-genpd-uaf-v1-1-0d9f3a34c4dc@jannau.net
> ---
> drivers/video/fbdev/simplefb.c | 31 +++++++++++++++++++++++--------
> 1 file changed, 23 insertions(+), 8 deletions(-)
applied to fbdev git tree.
Thanks!
Helge
PS: Janne, if you want to push yourself via drm-misc, just let me know and I drop it...
On Tue, Sep 30, 2025 at 09:12:21PM +0200, Helge Deller wrote:
> On 9/15/25 08:36, Janne Grunau wrote:
> > The pm_domain cleanup can not be devres managed as it uses struct
> > simplefb_par which is allocated within struct fb_info by
> > framebuffer_alloc(). This allocation is explicitly freed by
> > unregister_framebuffer() in simplefb_remove().
> > Devres managed cleanup runs after the device remove call and thus can no
> > longer access struct simplefb_par.
> > Call simplefb_detach_genpds() explicitly from simplefb_destroy() like
> > the cleanup functions for clocks and regulators.
> >
> > Fixes an use after free on M2 Mac mini during
> > aperture_remove_conflicting_devices() using the downstream asahi kernel
> > with Debian's kernel config. For unknown reasons this started to
> > consistently dereference an invalid pointer in v6.16.3 based kernels.
> >
> > [ 6.736134] BUG: KASAN: slab-use-after-free in simplefb_detach_genpds+0x58/0x220
> > [ 6.743545] Read of size 4 at addr ffff8000304743f0 by task (udev-worker)/227
> > [ 6.750697]
> > [ 6.752182] CPU: 6 UID: 0 PID: 227 Comm: (udev-worker) Tainted: G S 6.16.3-asahi+ #16 PREEMPTLAZY
> > [ 6.752186] Tainted: [S]=CPU_OUT_OF_SPEC
> > [ 6.752187] Hardware name: Apple Mac mini (M2, 2023) (DT)
> > [ 6.752189] Call trace:
> > [ 6.752190] show_stack+0x34/0x98 (C)
> > [ 6.752194] dump_stack_lvl+0x60/0x80
> > [ 6.752197] print_report+0x17c/0x4d8
> > [ 6.752201] kasan_report+0xb4/0x100
> > [ 6.752206] __asan_report_load4_noabort+0x20/0x30
> > [ 6.752209] simplefb_detach_genpds+0x58/0x220
> > [ 6.752213] devm_action_release+0x50/0x98
> > [ 6.752216] release_nodes+0xd0/0x2c8
> > [ 6.752219] devres_release_all+0xfc/0x178
> > [ 6.752221] device_unbind_cleanup+0x28/0x168
> > [ 6.752224] device_release_driver_internal+0x34c/0x470
> > [ 6.752228] device_release_driver+0x20/0x38
> > [ 6.752231] bus_remove_device+0x1b0/0x380
> > [ 6.752234] device_del+0x314/0x820
> > [ 6.752238] platform_device_del+0x3c/0x1e8
> > [ 6.752242] platform_device_unregister+0x20/0x50
> > [ 6.752246] aperture_detach_platform_device+0x1c/0x30
> > [ 6.752250] aperture_detach_devices+0x16c/0x290
> > [ 6.752253] aperture_remove_conflicting_devices+0x34/0x50
> > ...
> > [ 6.752343]
> > [ 6.967409] Allocated by task 62:
> > [ 6.970724] kasan_save_stack+0x3c/0x70
> > [ 6.974560] kasan_save_track+0x20/0x40
> > [ 6.978397] kasan_save_alloc_info+0x40/0x58
> > [ 6.982670] __kasan_kmalloc+0xd4/0xd8
> > [ 6.986420] __kmalloc_noprof+0x194/0x540
> > [ 6.990432] framebuffer_alloc+0xc8/0x130
> > [ 6.994444] simplefb_probe+0x258/0x2378
> > ...
> > [ 7.054356]
> > [ 7.055838] Freed by task 227:
> > [ 7.058891] kasan_save_stack+0x3c/0x70
> > [ 7.062727] kasan_save_track+0x20/0x40
> > [ 7.066565] kasan_save_free_info+0x4c/0x80
> > [ 7.070751] __kasan_slab_free+0x6c/0xa0
> > [ 7.074675] kfree+0x10c/0x380
> > [ 7.077727] framebuffer_release+0x5c/0x90
> > [ 7.081826] simplefb_destroy+0x1b4/0x2c0
> > [ 7.085837] put_fb_info+0x98/0x100
> > [ 7.089326] unregister_framebuffer+0x178/0x320
> > [ 7.093861] simplefb_remove+0x3c/0x60
> > [ 7.097611] platform_remove+0x60/0x98
> > [ 7.101361] device_remove+0xb8/0x160
> > [ 7.105024] device_release_driver_internal+0x2fc/0x470
> > [ 7.110256] device_release_driver+0x20/0x38
> > [ 7.114529] bus_remove_device+0x1b0/0x380
> > [ 7.118628] device_del+0x314/0x820
> > [ 7.122116] platform_device_del+0x3c/0x1e8
> > [ 7.126302] platform_device_unregister+0x20/0x50
> > [ 7.131012] aperture_detach_platform_device+0x1c/0x30
> > [ 7.136157] aperture_detach_devices+0x16c/0x290
> > [ 7.140779] aperture_remove_conflicting_devices+0x34/0x50
> > ...
> >
> > Reported-by: Daniel Huhardeaux <tech@tootai.net>
> > Cc: stable@vger.kernel.org
> > Fixes: 92a511a568e44 ("fbdev/simplefb: Add support for generic power-domains")
> > Signed-off-by: Janne Grunau <j@jannau.net>
> > ---
> > Changes in v3:
> > - release power-domains on probe errors
> > - set par->num_genpds when it's <= 1
> > - set par->num_genpds to 0 after detaching
> > - Link to v2: https://lore.kernel.org/r/20250908-simplefb-genpd-uaf-v2-1-f88a0d9d880f@jannau.net
> >
> > Changes in v2:
> > - reworked change due to missed use of `par->num_genpds` before setting
> > it. Missed in testing due to mixing up FB_SIMPLE and SYSFB_SIMPLEFB.
> > - Link to v1: https://lore.kernel.org/r/20250901-simplefb-genpd-uaf-v1-1-0d9f3a34c4dc@jannau.net
> > ---
> > drivers/video/fbdev/simplefb.c | 31 +++++++++++++++++++++++--------
> > 1 file changed, 23 insertions(+), 8 deletions(-)
>
> applied to fbdev git tree.
Thanks.
>
> PS: Janne, if you want to push yourself via drm-misc, just let me know and I drop it...
I won't. My request for commit access is still pending. I should fine
someone at xdc to ask about that.
Janne
Hi,
On 15-Sep-25 8:36 AM, Janne Grunau wrote:
> The pm_domain cleanup can not be devres managed as it uses struct
> simplefb_par which is allocated within struct fb_info by
> framebuffer_alloc(). This allocation is explicitly freed by
> unregister_framebuffer() in simplefb_remove().
> Devres managed cleanup runs after the device remove call and thus can no
> longer access struct simplefb_par.
> Call simplefb_detach_genpds() explicitly from simplefb_destroy() like
> the cleanup functions for clocks and regulators.
>
> Fixes an use after free on M2 Mac mini during
> aperture_remove_conflicting_devices() using the downstream asahi kernel
> with Debian's kernel config. For unknown reasons this started to
> consistently dereference an invalid pointer in v6.16.3 based kernels.
Thanks, this v3 patch looks good to me:
Reviewed-by: Hans de Goede <hansg@kernel.org>
I assume that you will push this do drm-misc yourself ?
Regards,
Hans
> [ 6.736134] BUG: KASAN: slab-use-after-free in simplefb_detach_genpds+0x58/0x220
> [ 6.743545] Read of size 4 at addr ffff8000304743f0 by task (udev-worker)/227
> [ 6.750697]
> [ 6.752182] CPU: 6 UID: 0 PID: 227 Comm: (udev-worker) Tainted: G S 6.16.3-asahi+ #16 PREEMPTLAZY
> [ 6.752186] Tainted: [S]=CPU_OUT_OF_SPEC
> [ 6.752187] Hardware name: Apple Mac mini (M2, 2023) (DT)
> [ 6.752189] Call trace:
> [ 6.752190] show_stack+0x34/0x98 (C)
> [ 6.752194] dump_stack_lvl+0x60/0x80
> [ 6.752197] print_report+0x17c/0x4d8
> [ 6.752201] kasan_report+0xb4/0x100
> [ 6.752206] __asan_report_load4_noabort+0x20/0x30
> [ 6.752209] simplefb_detach_genpds+0x58/0x220
> [ 6.752213] devm_action_release+0x50/0x98
> [ 6.752216] release_nodes+0xd0/0x2c8
> [ 6.752219] devres_release_all+0xfc/0x178
> [ 6.752221] device_unbind_cleanup+0x28/0x168
> [ 6.752224] device_release_driver_internal+0x34c/0x470
> [ 6.752228] device_release_driver+0x20/0x38
> [ 6.752231] bus_remove_device+0x1b0/0x380
> [ 6.752234] device_del+0x314/0x820
> [ 6.752238] platform_device_del+0x3c/0x1e8
> [ 6.752242] platform_device_unregister+0x20/0x50
> [ 6.752246] aperture_detach_platform_device+0x1c/0x30
> [ 6.752250] aperture_detach_devices+0x16c/0x290
> [ 6.752253] aperture_remove_conflicting_devices+0x34/0x50
> ...
> [ 6.752343]
> [ 6.967409] Allocated by task 62:
> [ 6.970724] kasan_save_stack+0x3c/0x70
> [ 6.974560] kasan_save_track+0x20/0x40
> [ 6.978397] kasan_save_alloc_info+0x40/0x58
> [ 6.982670] __kasan_kmalloc+0xd4/0xd8
> [ 6.986420] __kmalloc_noprof+0x194/0x540
> [ 6.990432] framebuffer_alloc+0xc8/0x130
> [ 6.994444] simplefb_probe+0x258/0x2378
> ...
> [ 7.054356]
> [ 7.055838] Freed by task 227:
> [ 7.058891] kasan_save_stack+0x3c/0x70
> [ 7.062727] kasan_save_track+0x20/0x40
> [ 7.066565] kasan_save_free_info+0x4c/0x80
> [ 7.070751] __kasan_slab_free+0x6c/0xa0
> [ 7.074675] kfree+0x10c/0x380
> [ 7.077727] framebuffer_release+0x5c/0x90
> [ 7.081826] simplefb_destroy+0x1b4/0x2c0
> [ 7.085837] put_fb_info+0x98/0x100
> [ 7.089326] unregister_framebuffer+0x178/0x320
> [ 7.093861] simplefb_remove+0x3c/0x60
> [ 7.097611] platform_remove+0x60/0x98
> [ 7.101361] device_remove+0xb8/0x160
> [ 7.105024] device_release_driver_internal+0x2fc/0x470
> [ 7.110256] device_release_driver+0x20/0x38
> [ 7.114529] bus_remove_device+0x1b0/0x380
> [ 7.118628] device_del+0x314/0x820
> [ 7.122116] platform_device_del+0x3c/0x1e8
> [ 7.126302] platform_device_unregister+0x20/0x50
> [ 7.131012] aperture_detach_platform_device+0x1c/0x30
> [ 7.136157] aperture_detach_devices+0x16c/0x290
> [ 7.140779] aperture_remove_conflicting_devices+0x34/0x50
> ...
>
> Reported-by: Daniel Huhardeaux <tech@tootai.net>
> Cc: stable@vger.kernel.org
> Fixes: 92a511a568e44 ("fbdev/simplefb: Add support for generic power-domains")
> Signed-off-by: Janne Grunau <j@jannau.net>
> ---
> Changes in v3:
> - release power-domains on probe errors
> - set par->num_genpds when it's <= 1
> - set par->num_genpds to 0 after detaching
> - Link to v2: https://lore.kernel.org/r/20250908-simplefb-genpd-uaf-v2-1-f88a0d9d880f@jannau.net
>
> Changes in v2:
> - reworked change due to missed use of `par->num_genpds` before setting
> it. Missed in testing due to mixing up FB_SIMPLE and SYSFB_SIMPLEFB.
> - Link to v1: https://lore.kernel.org/r/20250901-simplefb-genpd-uaf-v1-1-0d9f3a34c4dc@jannau.net
> ---
> drivers/video/fbdev/simplefb.c | 31 +++++++++++++++++++++++--------
> 1 file changed, 23 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c
> index 1893815dc67f4c1403eea42c0e10a7ead4d96ba9..6acf5a00c2bacfab89c3a63bab3d8b1b091a20a8 100644
> --- a/drivers/video/fbdev/simplefb.c
> +++ b/drivers/video/fbdev/simplefb.c
> @@ -93,6 +93,7 @@ struct simplefb_par {
>
> static void simplefb_clocks_destroy(struct simplefb_par *par);
> static void simplefb_regulators_destroy(struct simplefb_par *par);
> +static void simplefb_detach_genpds(void *res);
>
> /*
> * fb_ops.fb_destroy is called by the last put_fb_info() call at the end
> @@ -105,6 +106,7 @@ static void simplefb_destroy(struct fb_info *info)
>
> simplefb_regulators_destroy(info->par);
> simplefb_clocks_destroy(info->par);
> + simplefb_detach_genpds(info->par);
> if (info->screen_base)
> iounmap(info->screen_base);
>
> @@ -445,13 +447,14 @@ static void simplefb_detach_genpds(void *res)
> if (!IS_ERR_OR_NULL(par->genpds[i]))
> dev_pm_domain_detach(par->genpds[i], true);
> }
> + par->num_genpds = 0;
> }
>
> static int simplefb_attach_genpds(struct simplefb_par *par,
> struct platform_device *pdev)
> {
> struct device *dev = &pdev->dev;
> - unsigned int i;
> + unsigned int i, num_genpds;
> int err;
>
> err = of_count_phandle_with_args(dev->of_node, "power-domains",
> @@ -465,26 +468,35 @@ static int simplefb_attach_genpds(struct simplefb_par *par,
> return err;
> }
>
> - par->num_genpds = err;
> + num_genpds = err;
>
> /*
> * Single power-domain devices are handled by the driver core, so
> * nothing to do here.
> */
> - if (par->num_genpds <= 1)
> + if (num_genpds <= 1) {
> + par->num_genpds = num_genpds;
> return 0;
> + }
>
> - par->genpds = devm_kcalloc(dev, par->num_genpds, sizeof(*par->genpds),
> + par->genpds = devm_kcalloc(dev, num_genpds, sizeof(*par->genpds),
> GFP_KERNEL);
> if (!par->genpds)
> return -ENOMEM;
>
> - par->genpd_links = devm_kcalloc(dev, par->num_genpds,
> + par->genpd_links = devm_kcalloc(dev, num_genpds,
> sizeof(*par->genpd_links),
> GFP_KERNEL);
> if (!par->genpd_links)
> return -ENOMEM;
>
> + /*
> + * Set par->num_genpds only after genpds and genpd_links are allocated
> + * to exit early from simplefb_detach_genpds() without full
> + * initialisation.
> + */
> + par->num_genpds = num_genpds;
> +
> for (i = 0; i < par->num_genpds; i++) {
> par->genpds[i] = dev_pm_domain_attach_by_id(dev, i);
> if (IS_ERR(par->genpds[i])) {
> @@ -506,9 +518,10 @@ static int simplefb_attach_genpds(struct simplefb_par *par,
> dev_warn(dev, "failed to link power-domain %u\n", i);
> }
>
> - return devm_add_action_or_reset(dev, simplefb_detach_genpds, par);
> + return 0;
> }
> #else
> +static void simplefb_detach_genpds(void *res) { }
> static int simplefb_attach_genpds(struct simplefb_par *par,
> struct platform_device *pdev)
> {
> @@ -622,18 +635,20 @@ static int simplefb_probe(struct platform_device *pdev)
> ret = devm_aperture_acquire_for_platform_device(pdev, par->base, par->size);
> if (ret) {
> dev_err(&pdev->dev, "Unable to acquire aperture: %d\n", ret);
> - goto error_regulators;
> + goto error_genpds;
> }
> ret = register_framebuffer(info);
> if (ret < 0) {
> dev_err(&pdev->dev, "Unable to register simplefb: %d\n", ret);
> - goto error_regulators;
> + goto error_genpds;
> }
>
> dev_info(&pdev->dev, "fb%d: simplefb registered!\n", info->node);
>
> return 0;
>
> +error_genpds:
> + simplefb_detach_genpds(par);
> error_regulators:
> simplefb_regulators_destroy(par);
> error_clocks:
>
> ---
> base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
> change-id: 20250901-simplefb-genpd-uaf-352704761a29
>
> Best regards,
On Mon, Sep 15, 2025 at 02:19:30PM +0200, Hans de Goede wrote: > Hi, > > On 15-Sep-25 8:36 AM, Janne Grunau wrote: > > The pm_domain cleanup can not be devres managed as it uses struct > > simplefb_par which is allocated within struct fb_info by > > framebuffer_alloc(). This allocation is explicitly freed by > > unregister_framebuffer() in simplefb_remove(). > > Devres managed cleanup runs after the device remove call and thus can no > > longer access struct simplefb_par. > > Call simplefb_detach_genpds() explicitly from simplefb_destroy() like > > the cleanup functions for clocks and regulators. > > > > Fixes an use after free on M2 Mac mini during > > aperture_remove_conflicting_devices() using the downstream asahi kernel > > with Debian's kernel config. For unknown reasons this started to > > consistently dereference an invalid pointer in v6.16.3 based kernels. > > Thanks, this v3 patch looks good to me: > > Reviewed-by: Hans de Goede <hansg@kernel.org> > > I assume that you will push this do drm-misc yourself ? I don't have drm-misc commit access yet. I took this as reminder to request access so I will either commit it myself or ask someone else in a couple of days (if nobody beats me to it). thanks, Janne
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