From: Al Viro <firstname.lastname@example.org> To: Linus Torvalds <email@example.com> Cc: Kirill Smelkov <firstname.lastname@example.org>, Arnd Bergmann <email@example.com>, Christoph Hellwig <firstname.lastname@example.org>, Greg Kroah-Hartman <email@example.com>, linux-fsdevel <firstname.lastname@example.org>, Linux List Kernel Mailing <email@example.com>, Rasmus Villemoes <firstname.lastname@example.org> Subject: Re: [PATCH 1/2] vfs: pass ppos=NULL to .read()/.write() of FMODE_STREAM files Date: Sat, 13 Apr 2019 18:38:36 +0100 [thread overview] Message-ID: <20190413173836.GO2217@ZenIV.linux.org.uk> (raw) In-Reply-To: <CAHk-=wg6Pn4M+7awA5WrHv2vVc5iLRL29ueG-NSwOCAyVT-OYQ@mail.gmail.com> On Sat, Apr 13, 2019 at 10:27:00AM -0700, Linus Torvalds wrote: > And I'd really like to have people (Al?) look at this and go "yeah, > makes sense". I do think that moving to a model where we wither have a > (properly locked) file position or no pos pointer at all is the right > model (ie I'd really like to get rid of the mixed case), but there > might be some practical problem that makes it impractical. > > Because the *real* problem with the mixed case is not "insane people > who do bad things might get odd results". No, the real problem with > the mixed case is that it could be a security issue (ie: one process > intentionally changes the file position just as another process is > going a 'read' and then avoids some limit test because the limit test > was done using the old 'pos' value but the actual IO was done using > the new one). > > So I suspect that we will have to either > > - get rid of the mixed case entirely (and do only properly locked > f_pos accesses or pass is a NULL f_pos) Good luck. Character devices get no exclusion often do use position are many might be buried behind several layers of indirection ... and often left unmaintained for a decade or two IOW, I don't see how you'd go about eliminating the mixed case...
next prev parent reply other threads:[~2019-04-13 17:38 UTC|newest] Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-03-26 22:20 [PATCH 1/3] fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock Kirill Smelkov 2019-03-26 23:22 ` [PATCH 3/3] fuse: Add FOPEN_STREAM and use stream_open() if filesystem returned that from open handler Kirill Smelkov 2019-04-24 7:13 ` [RESEND, PATCH " Kirill Smelkov [not found] ` <20190424160611.2A71321900@mail.kernel.org> 2019-04-24 19:16 ` Kirill Smelkov [not found] ` <email@example.com> 2019-03-27 6:54 ` [PATCH 2/3] *: convert stream-like files from nonseekable_open -> stream_open Lubomir Rintel 2019-03-27 16:58 ` [PATCH 1/3] fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock Juergen Gross 2019-04-06 17:07 ` Linus Torvalds 2019-04-07 20:04 ` Kirill Smelkov 2019-04-08 0:09 ` Linus Torvalds 2019-04-14 7:11 ` Kirill Smelkov [not found] ` <firstname.lastname@example.org> [not found] ` <20190409203807.GA13855@deco.navytux.spb.ru> [not found] ` <email@example.com> 2019-04-11 12:38 ` Kirill Smelkov 2019-04-11 16:22 ` Linus Torvalds 2019-04-12 12:42 ` Kirill Smelkov 2019-04-13 16:54 ` Kirill Smelkov 2019-04-13 16:54 ` [PATCH 1/2] vfs: pass ppos=NULL to .read()/.write() of FMODE_STREAM files Kirill Smelkov 2019-04-13 17:27 ` Linus Torvalds 2019-04-13 17:38 ` Al Viro [this message] 2019-04-13 18:44 ` Kirill Smelkov 2019-04-13 16:55 ` [PATCH 2/2] vfs: use &file->f_pos directly on files that have position Kirill Smelkov
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