Date: Sun, 8 Jul 2018 07:58:40 -0700 From: Christoph Hellwig <hch@...radead.org> To: Jens Axboe <axboe@...nel.dk> Cc: Christoph Hellwig <hch@...radead.org>, dgilbert@...erlog.com, Al Viro <viro@...IV.linux.org.uk>, Jann Horn <jannh@...gle.com>, FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>, "James E.J. Bottomley" <jejb@...ux.vnet.ibm.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, linux-block@...r.kernel.org, linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com, security@...nel.org Subject: Re: [PATCH] sg, bsg: mitigate read/write abuse, block uaccess in release On Thu, Jun 21, 2018 at 08:07:23AM -0600, Jens Axboe wrote: > I'd be fine with that, if we knew that nobody uses it. But that's > really hard to figure out. I did see Jann's source code scan, which > even if non-exhaustive, still shows at least one user of it. One is an example, and the other looks very close to an example, as far as I can tell it was Nic doing a bsg read/write WIP for a tgt module without anyone every picking up on it. I did add the tgt list to Cc and no one seemed to care about the bsg read/write support. Adding the tgt list back, but I doubt anyone ever actually used it. > How about we just make the write interface sync? Then any copy can > happen while the we block the task, and the read side is just > copying the header info back, or dumping it if the task didn't > read it before it went away. How is that going to work? As far as I can tell each I/O using bsg read/write needs a write and a read, so they need to pair and thus can't be a purely sync interface. It also doesn't help with the issue that bsg_write may possible write to user memory, which is highly unusal and asking for security issues itself. Either way, we should probably at very least apply a respun version of the patch from Jann to 4.18-rc and -stable while we keep discussing this. Jann, can you respin the bsg patch with the same changes as the now included sg one?
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