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; }
[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; }
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;
}
dri-devel@lists.freedesktop.org
-
Helge Deller -
Javier Martinez Canillas -
Pascal Ernster