From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3B3DD224B0B for ; Thu, 3 Apr 2025 14:30:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.251.105.195 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743690657; cv=none; b=VlHHBiV5D07rqVcqBqigUorqqtPObWAEk/z6MMGop6z3lAtFukbShVmdbZLqxY3BW/DmysKFuoWaEJCkLZmGMtaoH5XFMfwi13ZUO0H9VAaFkgXJfHWNkQWt+JD3wBHHv8kRnTFY5uaLzbCPEaAe3dSFPZHh8hqnGtR6IYeszgo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743690657; c=relaxed/simple; bh=8sUwQ/gR6C8FYDEcOLVuxKNcdIng4fl8px+2OUlTGhE=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=nzeDnfTDg0VmCQMC6itE7/5mlsV7Is9lRqGVaO6Mqbinp1nFVYYQM13dXvWnI20rLGq6q8pqilnQaE+bnebDNhhvZZratoWbxJwrRKzcdPAf29OODS1lHVavFLfFsb8Y7rphXXd7hMsREXSx5DdLV/sdz+pnEB8nl+IfX0gcAw4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=HtLx2qEg; arc=none smtp.client-ip=148.251.105.195 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="HtLx2qEg" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1743690653; bh=8sUwQ/gR6C8FYDEcOLVuxKNcdIng4fl8px+2OUlTGhE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=HtLx2qEgGJInf+4mIwGxb640gJQ9G39la8nrlQu0ClhNa+EBad6jC+4e1IUJSwlEP wKTWcANYgo0Jy0D9nrRqiC9YhwXZwCFo0aYX5BRqLSzxV/dUGW+mT2LV4tZ4Em0mnC YuymkuX02tMkQp6kkiOfeKbLD2a7GidqGXXN7rRaZfxSOW40WmVQootpiHVfh7gN1D tyqnsPA1wnlzZZOdSHFPTL8YE75L7pgDYGxRdJtBWykgd6KVeroqTNSjJ8BNtrkVP6 mkut3CqaTMscbi+fWiv97FYO2BkiUpMk7VAAY09rPL9hRgLOZpectai9G1A7m/lTnQ LfGuZELhvjV1g== Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by bali.collaboradmins.com (Postfix) with ESMTPSA id 08E1417E0391; Thu, 3 Apr 2025 16:30:52 +0200 (CEST) Date: Thu, 3 Apr 2025 16:30:47 +0200 From: Boris Brezillon To: Dmitry Osipenko Cc: Thomas Zimmermann , Lucas De Marchi , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com Subject: Re: [PATCH v1] drm/shmem-helper: Fix unsetting shmem vaddr while vmap refcount > 0 Message-ID: <20250403163047.63929f63@collabora.com> In-Reply-To: <20250403142633.484660-1-dmitry.osipenko@collabora.com> References: <20250403142633.484660-1-dmitry.osipenko@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 3 Apr 2025 17:26:33 +0300 Dmitry Osipenko wrote: > We switched to use refcount_t for vmaps and missed to change the vunmap > code to properly unset the vmap pointer, which is now cleared while vmap's > refcount > 0. Clear the cached vmap pointer only when refcounting drops to > zero to fix the bug. > > Fixes: e1fc39a92332 ("drm/shmem-helper: Use refcount_t for vmap_use_count") > Reported-by: Lucas De Marchi > Closes: https://lore.kernel.org/dri-devel/20250403105053.788b0f6e@collabora.com/T/#m3dca6d81bedc8d6146a56b82694624fbc6fa4c96 > Signed-off-by: Dmitry Osipenko Reviewed-by: Boris Brezillon > --- > drivers/gpu/drm/drm_gem_shmem_helper.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c > index 2d924d547a51..aa43265f4f4f 100644 > --- a/drivers/gpu/drm/drm_gem_shmem_helper.c > +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c > @@ -415,11 +415,11 @@ void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem, > > if (refcount_dec_and_test(&shmem->vmap_use_count)) { > vunmap(shmem->vaddr); > + shmem->vaddr = NULL; > + > drm_gem_shmem_unpin_locked(shmem); > } > } > - > - shmem->vaddr = NULL; > } > EXPORT_SYMBOL_GPL(drm_gem_shmem_vunmap_locked); >