| Message ID | 20210904064534.1919476-1-qiulaibin@huawei.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | [-next,SCSI] Fix NULL pointer dereference in handling for passthrough commands | expand |
On 9/3/21 23:45, Laibin Qiu wrote: > In passthrough path. If the command size for ioctl request from userspace > is 0. The original process will get cmd_len from cmd->cmnd, but It has > not been assigned at this time. So it will trigger a NULL pointer BUG. A Friday night in the middle of the merge window is not the best time to post a kernel patch. Anyway: Reviewed-by: Bart Van Assche <bvanassche@acm.org>
On 9/3/21 23:45, Laibin Qiu wrote: > cmd->cmd_len = scsi_req(req)->cmd_len; > + cmd->cmnd = scsi_req(req)->cmd; > if (cmd->cmd_len == 0) > cmd->cmd_len = scsi_command_size(cmd->cmnd); > - cmd->cmnd = scsi_req(req)->cmd; > cmd->transfersize = blk_rq_bytes(req); Thinking further about this: is there any code left that depends on scsi_setup_scsi_cmnd() setting cmd->cmd_len? Can the cmd->cmd_len assignment be removed from scsi_setup_scsi_cmnd()? Thanks, Bart.
On Mon, Sep 06, 2021 at 05:40:35PM -0700, Bart Van Assche wrote: > On 9/3/21 23:45, Laibin Qiu wrote: >> cmd->cmd_len = scsi_req(req)->cmd_len; >> + cmd->cmnd = scsi_req(req)->cmd; >> if (cmd->cmd_len == 0) >> cmd->cmd_len = scsi_command_size(cmd->cmnd); >> - cmd->cmnd = scsi_req(req)->cmd; >> cmd->transfersize = blk_rq_bytes(req); > > Thinking further about this: is there any code left that depends on > scsi_setup_scsi_cmnd() setting cmd->cmd_len? Can the cmd->cmd_len > assignment be removed from scsi_setup_scsi_cmnd()? cmd_len should never be 0 now, so I think we can remove it.
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 572673873ddf..53b47a9103d3 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -1174,9 +1174,9 @@ static blk_status_t scsi_setup_scsi_cmnd(struct scsi_device *sdev, } cmd->cmd_len = scsi_req(req)->cmd_len; + cmd->cmnd = scsi_req(req)->cmd; if (cmd->cmd_len == 0) cmd->cmd_len = scsi_command_size(cmd->cmnd); - cmd->cmnd = scsi_req(req)->cmd; cmd->transfersize = blk_rq_bytes(req); cmd->allowed = scsi_req(req)->retries; return BLK_STS_OK;
In passthrough path. If the command size for ioctl request from userspace is 0. The original process will get cmd_len from cmd->cmnd, but It has not been assigned at this time. So it will trigger a NULL pointer BUG. ------------[ cut here ]------------ BUG: kernel NULL pointer dereference, address: 0000000000000000 PF: supervisor read access in kernel mode PF: error_code(0x0000) - not-present page RIP: 0010:scsi_queue_rq+0xcb2/0x12b0 Call Trace: blk_mq_dispatch_rq_list+0x541/0xe90 __blk_mq_sched_dispatch_requests+0x1fe/0x2b0 blk_mq_sched_dispatch_requests+0xbf/0x130 __blk_mq_run_hw_queue+0x15b/0x230 __blk_mq_delay_run_hw_queue+0x18f/0x320 blk_mq_run_hw_queue+0x252/0x280 blk_mq_sched_insert_request+0x228/0x260 blk_execute_rq+0x111/0x160 sg_io+0x51a/0x740 scsi_cmd_ioctl+0x533/0x910 scsi_cmd_blk_ioctl+0xa1/0xb0 cdrom_ioctl+0x3f/0x2510 sr_block_ioctl+0x142/0x180 blkdev_ioctl+0x398/0x450 block_ioctl+0x6d/0x80 __se_sys_ioctl+0xd1/0x140 __x64_sys_ioctl+0x3f/0x50 do_syscall_64+0x37/0x50 entry_SYSCALL_64_after_hwframe+0x44/0xa9 We can trigger front BUG by ioctl blow. ------------[ cut here ]------------ sg_io_hdr_t *addr; addr = malloc(sizeof(sg_io_hdr_t)); memset(addr, 0, sizeof(sg_io_hdr_t)); addr->interface_id = 'S'; fd = open(/dev/sr0, O_RDONLY); // open a CD_ROM dev ioctl(fd, SG_IO, addr); // all zero sg_io_hdr_t will trigger this bug Fixes: 2ceda20f0a99a ("scsi: core: Move command size detection out of the fast path") Signed-off-by: Laibin Qiu <qiulaibin@huawei.com> --- drivers/scsi/scsi_lib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)