• Javier Martinez Canillas's avatar
    video: fbdev: vesafb: Fix a use-after-free due early fb_info cleanup · acde4003
    Javier Martinez Canillas authored
    Commit b3c9a924 ("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: b3c9a924 ("fbdev: vesafb: Cleanup fb_info in .fb_destroy rather than .remove")
    Reported-by: default avatarPascal Ernster <dri-devel@hardfalcon.net>
    Signed-off-by: default avatarJavier Martinez Canillas <javierm@redhat.com>
    Tested-by: default avatarPascal Ernster <dri-devel@hardfalcon.net>
    Signed-off-by: default avatarHelge Deller <deller@gmx.de>
    acde4003
vesafb.c 14.7 KB