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From: Linus Torvalds <[email protected]>
To: Christian Brauner <[email protected]>
Cc: Al Viro <[email protected]>,
	[email protected], [email protected],
	 [email protected], [email protected],
	 [email protected], [email protected], [email protected],
	 [email protected], [email protected],
	 [email protected], [email protected],
	 [email protected], [email protected],
	 [email protected],
	 [email protected]
Subject: Re: [PATCH] epoll: try to be a _bit_ better about file lifetimes
Date: Sat, 4 May 2024 08:53:47 -0700	[thread overview]
Message-ID: <CAHk-=whrSSNYVzTHNFDNGag_xcKuv=RaQUX8+n29kkic39DRuQ@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wirxPSQgRV1u7t4qS1t4ED7w7OeehdUSC-LYZXspqa49w@mail.gmail.com>

On Sat, 4 May 2024 at 08:40, Linus Torvalds
<[email protected]> wrote:
>
> And maybe it's even *only* dma-buf that does that fget() in its
> ->poll() function. Even *then* it's not a dma-buf.c bug.

They all do in the sense that they do

  poll_wait
    -> __pollwait
     -> get_file (*boom*)

but the boom is very small because the poll_wait() will be undone by
poll_freewait(), and normally poll/select has held the file count
elevated.

Except for epoll. Which leaves those pollwait entries around until
it's done - but again will be held up on the ep->mtx before it does
so.

So everybody does some f_count games, but possibly dma-buf is the only
one that ends up expecting to hold on to the f_count for longer
periods.

             Linus

  reply	other threads:[~2024-05-04 15:54 UTC|newest]

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-04-08  8:26 [syzbot] [fs?] [io-uring?] general protection fault in __ep_remove syzbot
2024-04-15 14:31 ` Jens Axboe
2024-04-15 14:57   ` Pavel Begunkov
2024-05-03 11:54 ` Bui Quang Minh
2024-05-03 18:26   ` get_file() unsafe under epoll (was Re: [syzbot] [fs?] [io-uring?] general protection fault in __ep_remove) Kees Cook
2024-05-03 18:49     ` Jens Axboe
2024-05-03 19:22       ` Kees Cook
2024-05-03 19:35         ` Jens Axboe
2024-05-03 19:59           ` Kees Cook
2024-05-03 20:28             ` Kees Cook
2024-05-03 21:11               ` Al Viro
2024-05-03 21:24                 ` Linus Torvalds
2024-05-03 21:30                   ` Al Viro
2024-05-06 17:46                   ` Stefan Metzmacher
2024-05-06 18:17                     ` Linus Torvalds
2024-05-08  8:47                       ` David Laight
2024-05-03 21:36                 ` Al Viro
2024-05-03 21:42                   ` Linus Torvalds
2024-05-03 21:53                     ` Al Viro
2024-05-06 12:23                       ` Daniel Vetter
2024-05-04  9:59             ` Christian Brauner
2024-05-03 21:11     ` [PATCH] epoll: try to be a _bit_ better about file lifetimes Linus Torvalds
2024-05-03 21:24       ` Al Viro
2024-05-03 21:33         ` Linus Torvalds
2024-05-03 21:45           ` Al Viro
2024-05-03 21:52             ` Linus Torvalds
2024-05-03 22:01               ` Al Viro
2024-05-03 22:07                 ` Al Viro
2024-05-03 23:16                   ` Linus Torvalds
2024-05-03 23:39                     ` Al Viro
2024-05-03 23:54                       ` Linus Torvalds
2024-05-04 10:44                       ` Christian Brauner
2024-05-03 22:46               ` Kees Cook
2024-05-03 23:03                 ` Al Viro
2024-05-03 23:23                   ` Kees Cook
2024-05-03 23:41                     ` Linus Torvalds
2024-05-04  9:19                       ` Christian Brauner
2024-05-06 12:37                       ` Daniel Vetter
2024-05-04  9:37           ` Christian Brauner
2024-05-04 15:32             ` Linus Torvalds
2024-05-04 15:40               ` Linus Torvalds
2024-05-04 15:53                 ` Linus Torvalds [this message]
2024-05-05 19:46                   ` Al Viro
2024-05-05 20:03                     ` Linus Torvalds
2024-05-05 20:30                       ` Al Viro
2024-05-05 20:53                         ` Linus Torvalds
2024-05-06 12:47                           ` Daniel Vetter
2024-05-06 14:46                             ` Christian Brauner
2024-05-07 10:58                               ` Daniel Vetter
2024-05-06 16:15                           ` Christian König
2024-05-05 10:50                 ` Christian Brauner
2024-05-05 16:46                   ` Linus Torvalds
2024-05-05 17:55                     ` [PATCH v2] epoll: be " Linus Torvalds
2024-05-05 18:04                       ` Jens Axboe
2024-05-05 20:01                       ` David Laight
2024-05-05 20:16                         ` Linus Torvalds
2024-05-05 20:12                     ` [PATCH] epoll: try to be a _bit_ " Al Viro
2024-05-06  8:45                     ` Christian Brauner
2024-05-06  9:26                       ` Christian Brauner
2024-05-06 14:19                         ` Christian Brauner
2024-05-07 21:02                       ` David Laight
2024-05-04 18:20               ` Linus Torvalds
2024-05-06 14:29                 ` [Linaro-mm-sig] " Christian König
2024-05-07 11:02                   ` Daniel Vetter
2024-05-07 16:46                     ` Linus Torvalds
2024-05-07 17:45                       ` Christian König
2024-05-08  7:51                         ` Michel Dänzer
2024-05-08  7:59                           ` Christian König
2024-05-08  8:23                         ` Christian Brauner
2024-05-08  9:10                           ` Christian König
2024-05-07 18:04                       ` Daniel Vetter
2024-05-07 19:07                         ` Linus Torvalds
2024-05-08  5:55                           ` Christian König
2024-05-08  8:32                             ` Daniel Vetter
2024-05-08 10:16                               ` Christian Brauner
2024-05-08  8:05                           ` Christian Brauner
2024-05-08 16:19                           ` Linus Torvalds
2024-05-08 17:14                             ` Linus Torvalds
2024-05-09 11:38                               ` Christian Brauner
2024-05-09 15:48                                 ` Linus Torvalds
2024-05-10  6:33                                   ` Christian Brauner
2024-05-08 10:08                   ` Christian Brauner
2024-05-08 15:45                     ` Daniel Vetter
2024-05-10 10:55                       ` Christian Brauner
2024-05-11 18:25                         ` David Laight
2024-05-05 17:31       ` Jens Axboe
2024-05-04  9:45     ` get_file() unsafe under epoll (was Re: [syzbot] [fs?] [io-uring?] general protection fault in __ep_remove) Christian Brauner

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