lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <53CBF240.1010807@gmail.com> Date: Sun, 20 Jul 2014 19:45:52 +0300 From: Boaz Harrosh <openosd@...il.com> To: Christoph Hellwig <hch@....de> CC: Jens Axboe <axboe@...nel.dk>, linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 2/2] block: support > 16 byte CDBs for SG_IO On 07/20/2014 04:27 PM, Christoph Hellwig wrote: > On Sun, Jul 20, 2014 at 02:47:49PM +0300, Boaz Harrosh wrote: >> >> So two things here: >> - hdr->cmd_len is char so can be MAX of 255. I understand that 4 bytes alignment is a SCSI >> thing so you found no point of checking any max size? > > I don't see any point to force the aligmnet - the devices need to reject > garbage commands, and if for some reason we'd see future commands > that are > 252 and < 255 we are prepared to handle them. > I agree >> - Why the zero alloc, if you are going to paste over it the exact same length. Now if like in scsi >> you need 4 bytes alignment and zero padding yes, but here you do not do this (and probably shouldn't). >> Hence why zero-alloc? > > No good reason except that's what sg and bsg do. > Ha sorry didn't look there. Looks redundant to me that's all <> >> Inside here: blk_fill_sghdr_rq() calls blk_verify_command() which does: >> (Below cmd[] is the buffer copied from user) >> >> /* Anybody who can open the device can do a read-safe command */ >> if (test_bit(cmd[0], filter->read_ok)) >> return 0; >> >> /* Write-safe commands require a writable open */ >> if (test_bit(cmd[0], filter->write_ok) && has_write_perm) >> return 0; >> >> Now I am not sure what type "Commands" you guys intend for these large commands >> but if they are say SCSI-VARLEN this test will not work. Also a user might fool >> the system with pretending to be "read" a device modifying command. >> >> I would pass len to this test function and only permit these above if command is >> <= 16. Any "special" large command is root only. > > Honestly that whole filter crap should never have been merged to start with, > you'll just need proper CAP_SYS_RAWIO for variable length commands. > > I agree. What I'm saying is - Are you sure that with current code as is we will not pass on large commands without the proper CAP_SYS_RAWIO. Should we not make sure and add: /* root can do any command. */ if (capable(CAP_SYS_RAWIO)) return 0; + + if (cmnd_len > BLK_MAX_CDB) + return -EPERM; Rrrr you are right. I finally get the filter code. Anything that is not "white-listed" is rejected. OK sorry for the noise. Reviewed-by: Boaz Harrosh <boaz@...xistor.com> Thanks Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists