From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:46236 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753294AbdDJM7p (ORCPT ); Mon, 10 Apr 2017 08:59:45 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: Sumit Semwal , Mauricio Faria de Oliveira , Brahadambal Srinivasan , Jens Axboe , Sasha Levin , Greg Kroah-Hartman , Jiri Slaby Subject: [patch added to 3.12-stable] block: allow WRITE_SAME commands with the SG_IO ioctl Date: Mon, 10 Apr 2017 14:59:02 +0200 Message-Id: <20170410125930.26495-25-jslaby@suse.cz> In-Reply-To: <20170410125930.26495-1-jslaby@suse.cz> References: <20170410125930.26495-1-jslaby@suse.cz> Sender: stable-owner@vger.kernel.org List-ID: From: Sumit Semwal This patch has been added to the 3.12 stable tree. If you have any objections, please let us know. =============== From: Mauricio Faria de Oliveira [ Upstream commit 25cdb64510644f3e854d502d69c73f21c6df88a9 ] The WRITE_SAME commands are not present in the blk_default_cmd_filter write_ok list, and thus are failed with -EPERM when the SG_IO ioctl() is executed without CAP_SYS_RAWIO capability (e.g., unprivileged users). [ sg_io() -> blk_fill_sghdr_rq() > blk_verify_command() -> -EPERM ] The problem can be reproduced with the sg_write_same command # sg_write_same --num 1 --xferlen 512 /dev/sda # # capsh --drop=cap_sys_rawio -- -c \ 'sg_write_same --num 1 --xferlen 512 /dev/sda' Write same: pass through os error: Operation not permitted # For comparison, the WRITE_VERIFY command does not observe this problem, since it is in that list: # capsh --drop=cap_sys_rawio -- -c \ 'sg_write_verify --num 1 --ilen 512 --lba 0 /dev/sda' # So, this patch adds the WRITE_SAME commands to the list, in order for the SG_IO ioctl to finish successfully: # capsh --drop=cap_sys_rawio -- -c \ 'sg_write_same --num 1 --xferlen 512 /dev/sda' # That case happens to be exercised by QEMU KVM guests with 'scsi-block' devices (qemu "-device scsi-block" [1], libvirt "" [2]), which employs the SG_IO ioctl() and runs as an unprivileged user (libvirt-qemu). In that scenario, when a filesystem (e.g., ext4) performs its zero-out calls, which are translated to write-same calls in the guest kernel, and then into SG_IO ioctls to the host kernel, SCSI I/O errors may be observed in the guest: [...] sd 0:0:0:0: [sda] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [...] sd 0:0:0:0: [sda] tag#0 Sense Key : Aborted Command [current] [...] sd 0:0:0:0: [sda] tag#0 Add. Sense: I/O process terminated [...] sd 0:0:0:0: [sda] tag#0 CDB: Write Same(10) 41 00 01 04 e0 78 00 00 08 00 [...] blk_update_request: I/O error, dev sda, sector 17096824 Links: [1] http://git.qemu.org/?p=qemu.git;a=commit;h=336a6915bc7089fb20fea4ba99972ad9a97c5f52 [2] https://libvirt.org/formatdomain.html#elementsDisks (see 'disk' -> 'device') Signed-off-by: Mauricio Faria de Oliveira Signed-off-by: Brahadambal Srinivasan Reported-by: Manjunatha H R Reviewed-by: Christoph Hellwig Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sumit Semwal Signed-off-by: Jiri Slaby --- block/scsi_ioctl.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c index 1b4988b4bc11..9bfbb51aa75e 100644 --- a/block/scsi_ioctl.c +++ b/block/scsi_ioctl.c @@ -175,6 +175,9 @@ static void blk_set_cmd_filter_defaults(struct blk_cmd_filter *filter) __set_bit(WRITE_16, filter->write_ok); __set_bit(WRITE_LONG, filter->write_ok); __set_bit(WRITE_LONG_2, filter->write_ok); + __set_bit(WRITE_SAME, filter->write_ok); + __set_bit(WRITE_SAME_16, filter->write_ok); + __set_bit(WRITE_SAME_32, filter->write_ok); __set_bit(ERASE, filter->write_ok); __set_bit(GPCMD_MODE_SELECT_10, filter->write_ok); __set_bit(MODE_SELECT, filter->write_ok); -- 2.12.2