From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 638DB21E082; Wed, 19 Mar 2025 14:39:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742395170; cv=none; b=JwrGAbZIosUVjHH/JutdxbSTY0Jp48Hu3jrzjeQ14f2OTkFlKOrnd2UTDu/lqz4Ybwb/5gJKHb1tr1xX0x9jmlFrR0SeL93iXoZFs8ml4O0bQRZv5zw8YQe4OcvyAcvb87P8HT3c00rjtGUnFbKUeikfZP1Nupva4j+ErH3lQr8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742395170; c=relaxed/simple; bh=glJpvshQcZ27C9BKugudcnC8SW+/8MSPGCTlys8/uwU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KcR29D+eAwfcaAzsc/DR1sy/tTPI8wjxV07ZmuqaHdRkcBMVp5yJnvLoVF41wZr2uJiStU9412A1PosfyIvkkKoMfkLCNxX8MJdNMAgU79SzzUoOPz1YzlIEm0g3MylwMH32/UMUo8R2w8e84fdSA/dcDm9EIz+HxKDxCRux+Wg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xjEZGCDV; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="xjEZGCDV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 38F29C4CEE4; Wed, 19 Mar 2025 14:39:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1742395170; bh=glJpvshQcZ27C9BKugudcnC8SW+/8MSPGCTlys8/uwU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xjEZGCDV30WjMSJYFpMtBkA4AkJEdANyEcrhgxvVNSz8M0HNsSrzF2mQFkx6bhLOi ypHfoBBK9gJq4I2HJZMWtV2u617sb1up1m6MmM0SrEVkFMsuYUV0bz1EzNmK/cljeY GUDO7SItI+pxTJhwjN2T85+iKvYeMFl8nF/qizVE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Liu Shixin , Sergey Senozhatsky , Jens Axboe , Minchan Kim , Andrew Morton , Jianqi Ren , He Zhe Subject: [PATCH 6.6 003/166] zram: fix NULL pointer in comp_algorithm_show() Date: Wed, 19 Mar 2025 07:29:34 -0700 Message-ID: <20250319143020.076417805@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250319143019.983527953@linuxfoundation.org> References: <20250319143019.983527953@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Liu Shixin commit f364cdeb38938f9d03061682b8ff3779dd1730e5 upstream. LTP reported a NULL pointer dereference as followed: CPU: 7 UID: 0 PID: 5995 Comm: cat Kdump: loaded Not tainted 6.12.0-rc6+ #3 Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : __pi_strcmp+0x24/0x140 lr : zcomp_available_show+0x60/0x100 [zram] sp : ffff800088b93b90 x29: ffff800088b93b90 x28: 0000000000000001 x27: 0000000000400cc0 x26: 0000000000000ffe x25: ffff80007b3e2388 x24: 0000000000000000 x23: ffff80007b3e2390 x22: ffff0004041a9000 x21: ffff80007b3e2900 x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: ffff80007b3e2900 x9 : ffff80007b3cb280 x8 : 0101010101010101 x7 : 0000000000000000 x6 : 0000000000000000 x5 : 0000000000000040 x4 : 0000000000000000 x3 : 00656c722d6f7a6c x2 : 0000000000000000 x1 : ffff80007b3e2900 x0 : 0000000000000000 Call trace: __pi_strcmp+0x24/0x140 comp_algorithm_show+0x40/0x70 [zram] dev_attr_show+0x28/0x80 sysfs_kf_seq_show+0x90/0x140 kernfs_seq_show+0x34/0x48 seq_read_iter+0x1d4/0x4e8 kernfs_fop_read_iter+0x40/0x58 new_sync_read+0x9c/0x168 vfs_read+0x1a8/0x1f8 ksys_read+0x74/0x108 __arm64_sys_read+0x24/0x38 invoke_syscall+0x50/0x120 el0_svc_common.constprop.0+0xc8/0xf0 do_el0_svc+0x24/0x38 el0_svc+0x38/0x138 el0t_64_sync_handler+0xc0/0xc8 el0t_64_sync+0x188/0x190 The zram->comp_algs[ZRAM_PRIMARY_COMP] can be NULL in zram_add() if comp_algorithm_set() has not been called. User can access the zram device by sysfs after device_add_disk(), so there is a time window to trigger the NULL pointer dereference. Move it ahead device_add_disk() to make sure when user can access the zram device, it is ready. comp_algorithm_set() is protected by zram->init_lock in other places and no such problem. Link: https://lkml.kernel.org/r/20241108100147.3776123-1-liushixin2@huawei.com Fixes: 7ac07a26dea7 ("zram: preparation for multi-zcomp support") Signed-off-by: Liu Shixin Reviewed-by: Sergey Senozhatsky Cc: Jens Axboe Cc: Minchan Kim Signed-off-by: Andrew Morton [This fix does not backport zram_comp_params_reset which was introduced after v6.6, in commit f2bac7ad187d ("zram: introduce zcomp_params structure")] Signed-off-by: Jianqi Ren Signed-off-by: He Zhe Signed-off-by: Greg Kroah-Hartman --- drivers/block/zram/zram_drv.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -2247,6 +2247,8 @@ static int zram_add(void) zram->disk->private_data = zram; snprintf(zram->disk->disk_name, 16, "zram%d", device_id); + comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor); + /* Actual capacity set using sysfs (/sys/block/zram/disksize */ set_capacity(zram->disk, 0); /* zram devices sort of resembles non-rotational disks */ @@ -2281,8 +2283,6 @@ static int zram_add(void) if (ret) goto out_cleanup_disk; - comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor); - zram_debugfs_register(zram); pr_info("Added device: %s\n", zram->disk->disk_name); return device_id;