From: Michal Hocko <firstname.lastname@example.org> To: Greg Kroah-Hartman <email@example.com> Cc: Kees Cook <firstname.lastname@example.org>, Andrew Morton <email@example.com>, Alexey Dobriyan <firstname.lastname@example.org>, Lee Duncan <email@example.com>, Chris Leech <firstname.lastname@example.org>, Adam Nichols <email@example.com>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, Uladzislau Rezki <email@example.com> Subject: Re: [PATCH v2] seq_file: Unconditionally use vmalloc for buffer Date: Wed, 17 Mar 2021 15:44:16 +0100 [thread overview] Message-ID: <YFIVwPWTo48ITkHs@dhcp22.suse.cz> (raw) In-Reply-To: <YFIFY7mj65sStba1@kroah.com> On Wed 17-03-21 14:34:27, Greg KH wrote: > On Wed, Mar 17, 2021 at 01:08:21PM +0100, Michal Hocko wrote: > > Btw. I still have problems with the approach. seq_file is intended to > > provide safe way to dump values to the userspace. Sacrificing > > performance just because of some abuser seems like a wrong way to go as > > Al pointed out earlier. Can we simply stop the abuse and disallow to > > manipulate the buffer directly? I do realize this might be more tricky > > for reasons mentioned in other emails but this is definitely worth > > doing. > > We have to provide a buffer to "write into" somehow, so what is the best > way to stop "abuse" like this? What is wrong about using seq_* interface directly? > Right now, we do have helper functions, sysfs_emit(), that know to stop > the overflow of the buffer size, but porting the whole kernel to them is > going to take a bunch of churn, for almost no real benefit except a > potential random driver that might be doing bad things here that we have > not noticed yet. I am not familiar with sysfs, I just got lost in all the indirection but replacing buffer by the seq_file and operate on that should be possible, no? -- Michal Hocko SUSE Labs
next prev parent reply other threads:[~2021-03-17 14:45 UTC|newest] Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-03-15 17:48 Kees Cook 2021-03-15 18:33 ` Al Viro 2021-03-15 20:43 ` Kees Cook 2021-03-16 7:24 ` Greg Kroah-Hartman 2021-03-16 12:43 ` Al Viro 2021-03-16 12:55 ` Greg Kroah-Hartman 2021-03-16 13:01 ` Michal Hocko 2021-03-16 19:18 ` Kees Cook 2021-03-17 10:44 ` Greg Kroah-Hartman 2021-03-16 8:31 ` Michal Hocko 2021-03-16 19:08 ` Kees Cook 2021-03-17 12:08 ` Michal Hocko 2021-03-17 13:34 ` Greg Kroah-Hartman 2021-03-17 14:44 ` Michal Hocko [this message] 2021-03-17 14:56 ` Greg Kroah-Hartman 2021-03-17 15:20 ` Michal Hocko 2021-03-17 15:38 ` Greg Kroah-Hartman 2021-03-17 15:48 ` Michal Hocko 2021-03-17 21:30 ` Kees Cook 2021-03-18 8:07 ` Greg Kroah-Hartman 2021-03-18 15:51 ` Kees Cook 2021-03-18 17:56 ` Greg Kroah-Hartman 2021-03-19 14:07 ` [seq_file] 5fd6060e50: stress-ng.eventfd.ops_per_sec -49.1% regression kernel test robot 2021-03-19 19:31 ` Kees Cook
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