* [PATCH] fbdev: vesafb: Fix a use-after-free due early fb_info cleanup
@ 2022-05-26 19:47 ` Javier Martinez Canillas
0 siblings, 0 replies; 6+ messages in thread
From: Javier Martinez Canillas @ 2022-05-26 19:47 UTC (permalink / raw)
To: linux-kernel
Cc: Pascal Ernster, Javier Martinez Canillas, Daniel Vetter,
Helge Deller, Thomas Zimmermann, dri-devel, linux-fbdev
Commit b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather
than .remove") fixed a use-after-free error due the vesafb driver freeing
the fb_info in the .remove handler instead of doing it in .fb_destroy.
This can happen if the .fb_destroy callback is executed after the .remove
callback, since the former tries to access a pointer freed by the latter.
But that change didn't take into account that another possible scenario is
that .fb_destroy is called before the .remove callback. For example, if no
process has the fbdev chardev opened by the time the driver is removed.
If that's the case, fb_info will be freed when unregister_framebuffer() is
called, making the fb_info pointer accessed in vesafb_remove() after that
to no longer be valid.
To prevent that, move the expression containing the info->par to happen
before the unregister_framebuffer() function call.
Fixes: b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather than .remove")
Reported-by: Pascal Ernster <dri-devel@hardfalcon.net>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---
drivers/video/fbdev/vesafb.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/video/fbdev/vesafb.c b/drivers/video/fbdev/vesafb.c
index e25e8de5ff67..929d4775cb4b 100644
--- a/drivers/video/fbdev/vesafb.c
+++ b/drivers/video/fbdev/vesafb.c
@@ -490,11 +490,12 @@ static int vesafb_remove(struct platform_device *pdev)
{
struct fb_info *info = platform_get_drvdata(pdev);
- /* vesafb_destroy takes care of info cleanup */
- unregister_framebuffer(info);
if (((struct vesafb_par *)(info->par))->region)
release_region(0x3c0, 32);
+ /* vesafb_destroy takes care of info cleanup */
+ unregister_framebuffer(info);
+
return 0;
}
--
2.36.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH] fbdev: vesafb: Fix a use-after-free due early fb_info cleanup
@ 2022-05-26 19:47 ` Javier Martinez Canillas
0 siblings, 0 replies; 6+ messages in thread
From: Javier Martinez Canillas @ 2022-05-26 19:47 UTC (permalink / raw)
To: linux-kernel
Cc: linux-fbdev, Daniel Vetter, Helge Deller,
Javier Martinez Canillas, dri-devel, Pascal Ernster,
Thomas Zimmermann
Commit b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather
than .remove") fixed a use-after-free error due the vesafb driver freeing
the fb_info in the .remove handler instead of doing it in .fb_destroy.
This can happen if the .fb_destroy callback is executed after the .remove
callback, since the former tries to access a pointer freed by the latter.
But that change didn't take into account that another possible scenario is
that .fb_destroy is called before the .remove callback. For example, if no
process has the fbdev chardev opened by the time the driver is removed.
If that's the case, fb_info will be freed when unregister_framebuffer() is
called, making the fb_info pointer accessed in vesafb_remove() after that
to no longer be valid.
To prevent that, move the expression containing the info->par to happen
before the unregister_framebuffer() function call.
Fixes: b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather than .remove")
Reported-by: Pascal Ernster <dri-devel@hardfalcon.net>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
---
drivers/video/fbdev/vesafb.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/video/fbdev/vesafb.c b/drivers/video/fbdev/vesafb.c
index e25e8de5ff67..929d4775cb4b 100644
--- a/drivers/video/fbdev/vesafb.c
+++ b/drivers/video/fbdev/vesafb.c
@@ -490,11 +490,12 @@ static int vesafb_remove(struct platform_device *pdev)
{
struct fb_info *info = platform_get_drvdata(pdev);
- /* vesafb_destroy takes care of info cleanup */
- unregister_framebuffer(info);
if (((struct vesafb_par *)(info->par))->region)
release_region(0x3c0, 32);
+ /* vesafb_destroy takes care of info cleanup */
+ unregister_framebuffer(info);
+
return 0;
}
--
2.36.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] fbdev: vesafb: Fix a use-after-free due early fb_info cleanup
2022-05-26 19:47 ` Javier Martinez Canillas
@ 2022-05-26 20:03 ` Pascal Ernster
-1 siblings, 0 replies; 6+ messages in thread
From: Pascal Ernster @ 2022-05-26 20:03 UTC (permalink / raw)
To: Javier Martinez Canillas, linux-kernel
Cc: Daniel Vetter, Helge Deller, Thomas Zimmermann, dri-devel, linux-fbdev
[2022-05-26 21:47:52] Javier Martinez Canillas:
> Commit b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather
> than .remove") fixed a use-after-free error due the vesafb driver freeing
> the fb_info in the .remove handler instead of doing it in .fb_destroy.
>
> This can happen if the .fb_destroy callback is executed after the .remove
> callback, since the former tries to access a pointer freed by the latter.
>
> But that change didn't take into account that another possible scenario is
> that .fb_destroy is called before the .remove callback. For example, if no
> process has the fbdev chardev opened by the time the driver is removed.
>
> If that's the case, fb_info will be freed when unregister_framebuffer() is
> called, making the fb_info pointer accessed in vesafb_remove() after that
> to no longer be valid.
>
> To prevent that, move the expression containing the info->par to happen
> before the unregister_framebuffer() function call.
>
> Fixes: b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather than .remove")
> Reported-by: Pascal Ernster <dri-devel@hardfalcon.net>
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Tested on a bare metal machine and on a test VM that had both crashed
when booting a kernel lacking this patch.
Again, thanks a lot for the quick fix! :)
Tested-by: Pascal Ernster <dri-devel@hardfalcon.net>
> ---
>
> drivers/video/fbdev/vesafb.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/video/fbdev/vesafb.c b/drivers/video/fbdev/vesafb.c
> index e25e8de5ff67..929d4775cb4b 100644
> --- a/drivers/video/fbdev/vesafb.c
> +++ b/drivers/video/fbdev/vesafb.c
> @@ -490,11 +490,12 @@ static int vesafb_remove(struct platform_device *pdev)
> {
> struct fb_info *info = platform_get_drvdata(pdev);
>
> - /* vesafb_destroy takes care of info cleanup */
> - unregister_framebuffer(info);
> if (((struct vesafb_par *)(info->par))->region)
> release_region(0x3c0, 32);
>
> + /* vesafb_destroy takes care of info cleanup */
> + unregister_framebuffer(info);
> +
> return 0;
> }
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fbdev: vesafb: Fix a use-after-free due early fb_info cleanup
@ 2022-05-26 20:03 ` Pascal Ernster
0 siblings, 0 replies; 6+ messages in thread
From: Pascal Ernster @ 2022-05-26 20:03 UTC (permalink / raw)
To: Javier Martinez Canillas, linux-kernel
Cc: Daniel Vetter, Helge Deller, dri-devel, Thomas Zimmermann, linux-fbdev
[2022-05-26 21:47:52] Javier Martinez Canillas:
> Commit b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather
> than .remove") fixed a use-after-free error due the vesafb driver freeing
> the fb_info in the .remove handler instead of doing it in .fb_destroy.
>
> This can happen if the .fb_destroy callback is executed after the .remove
> callback, since the former tries to access a pointer freed by the latter.
>
> But that change didn't take into account that another possible scenario is
> that .fb_destroy is called before the .remove callback. For example, if no
> process has the fbdev chardev opened by the time the driver is removed.
>
> If that's the case, fb_info will be freed when unregister_framebuffer() is
> called, making the fb_info pointer accessed in vesafb_remove() after that
> to no longer be valid.
>
> To prevent that, move the expression containing the info->par to happen
> before the unregister_framebuffer() function call.
>
> Fixes: b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather than .remove")
> Reported-by: Pascal Ernster <dri-devel@hardfalcon.net>
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Tested on a bare metal machine and on a test VM that had both crashed
when booting a kernel lacking this patch.
Again, thanks a lot for the quick fix! :)
Tested-by: Pascal Ernster <dri-devel@hardfalcon.net>
> ---
>
> drivers/video/fbdev/vesafb.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/video/fbdev/vesafb.c b/drivers/video/fbdev/vesafb.c
> index e25e8de5ff67..929d4775cb4b 100644
> --- a/drivers/video/fbdev/vesafb.c
> +++ b/drivers/video/fbdev/vesafb.c
> @@ -490,11 +490,12 @@ static int vesafb_remove(struct platform_device *pdev)
> {
> struct fb_info *info = platform_get_drvdata(pdev);
>
> - /* vesafb_destroy takes care of info cleanup */
> - unregister_framebuffer(info);
> if (((struct vesafb_par *)(info->par))->region)
> release_region(0x3c0, 32);
>
> + /* vesafb_destroy takes care of info cleanup */
> + unregister_framebuffer(info);
> +
> return 0;
> }
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fbdev: vesafb: Fix a use-after-free due early fb_info cleanup
2022-05-26 19:47 ` Javier Martinez Canillas
@ 2022-05-28 17:28 ` Helge Deller
-1 siblings, 0 replies; 6+ messages in thread
From: Helge Deller @ 2022-05-28 17:28 UTC (permalink / raw)
To: Javier Martinez Canillas, linux-kernel
Cc: Pascal Ernster, Daniel Vetter, Thomas Zimmermann, dri-devel, linux-fbdev
On 5/26/22 21:47, Javier Martinez Canillas wrote:
> Commit b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather
> than .remove") fixed a use-after-free error due the vesafb driver freeing
> the fb_info in the .remove handler instead of doing it in .fb_destroy.
>
> This can happen if the .fb_destroy callback is executed after the .remove
> callback, since the former tries to access a pointer freed by the latter.
>
> But that change didn't take into account that another possible scenario is
> that .fb_destroy is called before the .remove callback. For example, if no
> process has the fbdev chardev opened by the time the driver is removed.
>
> If that's the case, fb_info will be freed when unregister_framebuffer() is
> called, making the fb_info pointer accessed in vesafb_remove() after that
> to no longer be valid.
>
> To prevent that, move the expression containing the info->par to happen
> before the unregister_framebuffer() function call.
>
> Fixes: b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather than .remove")
> Reported-by: Pascal Ernster <dri-devel@hardfalcon.net>
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
applied to the fbdev git tree.
Thanks!
Helge
> ---
>
> drivers/video/fbdev/vesafb.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/video/fbdev/vesafb.c b/drivers/video/fbdev/vesafb.c
> index e25e8de5ff67..929d4775cb4b 100644
> --- a/drivers/video/fbdev/vesafb.c
> +++ b/drivers/video/fbdev/vesafb.c
> @@ -490,11 +490,12 @@ static int vesafb_remove(struct platform_device *pdev)
> {
> struct fb_info *info = platform_get_drvdata(pdev);
>
> - /* vesafb_destroy takes care of info cleanup */
> - unregister_framebuffer(info);
> if (((struct vesafb_par *)(info->par))->region)
> release_region(0x3c0, 32);
>
> + /* vesafb_destroy takes care of info cleanup */
> + unregister_framebuffer(info);
> +
> return 0;
> }
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fbdev: vesafb: Fix a use-after-free due early fb_info cleanup
@ 2022-05-28 17:28 ` Helge Deller
0 siblings, 0 replies; 6+ messages in thread
From: Helge Deller @ 2022-05-28 17:28 UTC (permalink / raw)
To: Javier Martinez Canillas, linux-kernel
Cc: Daniel Vetter, dri-devel, Pascal Ernster, Thomas Zimmermann, linux-fbdev
On 5/26/22 21:47, Javier Martinez Canillas wrote:
> Commit b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather
> than .remove") fixed a use-after-free error due the vesafb driver freeing
> the fb_info in the .remove handler instead of doing it in .fb_destroy.
>
> This can happen if the .fb_destroy callback is executed after the .remove
> callback, since the former tries to access a pointer freed by the latter.
>
> But that change didn't take into account that another possible scenario is
> that .fb_destroy is called before the .remove callback. For example, if no
> process has the fbdev chardev opened by the time the driver is removed.
>
> If that's the case, fb_info will be freed when unregister_framebuffer() is
> called, making the fb_info pointer accessed in vesafb_remove() after that
> to no longer be valid.
>
> To prevent that, move the expression containing the info->par to happen
> before the unregister_framebuffer() function call.
>
> Fixes: b3c9a924aab6 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather than .remove")
> Reported-by: Pascal Ernster <dri-devel@hardfalcon.net>
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
applied to the fbdev git tree.
Thanks!
Helge
> ---
>
> drivers/video/fbdev/vesafb.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/video/fbdev/vesafb.c b/drivers/video/fbdev/vesafb.c
> index e25e8de5ff67..929d4775cb4b 100644
> --- a/drivers/video/fbdev/vesafb.c
> +++ b/drivers/video/fbdev/vesafb.c
> @@ -490,11 +490,12 @@ static int vesafb_remove(struct platform_device *pdev)
> {
> struct fb_info *info = platform_get_drvdata(pdev);
>
> - /* vesafb_destroy takes care of info cleanup */
> - unregister_framebuffer(info);
> if (((struct vesafb_par *)(info->par))->region)
> release_region(0x3c0, 32);
>
> + /* vesafb_destroy takes care of info cleanup */
> + unregister_framebuffer(info);
> +
> return 0;
> }
>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-05-28 17:28 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-05-26 19:47 [PATCH] fbdev: vesafb: Fix a use-after-free due early fb_info cleanup Javier Martinez Canillas
2022-05-26 19:47 ` Javier Martinez Canillas
2022-05-26 20:03 ` Pascal Ernster
2022-05-26 20:03 ` Pascal Ernster
2022-05-28 17:28 ` Helge Deller
2022-05-28 17:28 ` Helge Deller
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