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    Subject[PATCH 5.15 020/102] fbdev: efifb: Fix a use-after-free due early fb_info cleanup
    Date
    From: Javier Martinez Canillas <javierm@redhat.com>

    [ Upstream commit 1b5853dfab7fdde450f00f145327342238135c8a ]

    Commit d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather
    than .remove") attempted to fix a use-after-free error due driver freeing
    the fb_info in the .remove handler instead of doing it in .fb_destroy.

    But ironically that change introduced yet another use-after-free since the
    fb_info was still used after the free.

    This should fix for good by freeing the fb_info at the end of the handler.

    Fixes: d258d00fb9c7 ("fbdev: efifb: Cleanup fb_info in .fb_destroy rather than .remove")
    Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
    Reported-by: Andrzej Hajda <andrzej.hajda@intel.com>
    Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
    Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
    Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
    Reviewed-by: Thomas Zimmermann <tzimemrmann@suse.de>
    Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20220506132225.588379-1-javierm@redhat.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/video/fbdev/efifb.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
    index cfa3dc0b4eee..b3d5f884c544 100644
    --- a/drivers/video/fbdev/efifb.c
    +++ b/drivers/video/fbdev/efifb.c
    @@ -259,12 +259,12 @@ static void efifb_destroy(struct fb_info *info)
    memunmap(info->screen_base);
    }

    - framebuffer_release(info);
    -
    if (request_mem_succeeded)
    release_mem_region(info->apertures->ranges[0].base,
    info->apertures->ranges[0].size);
    fb_dealloc_cmap(&info->cmap);
    +
    + framebuffer_release(info);
    }

    static const struct fb_ops efifb_ops = {
    --
    2.35.1


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