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From: "Michael K. Edwards" <medwards.linux@gmail.com>
To: "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: sys_write() racy for multi-threaded append?
Date: Thu, 8 Mar 2007 15:08:17 -0800	[thread overview]
Message-ID: <f2b55d220703081508r3d8d033cu99f53104943d16cb@mail.gmail.com> (raw)

from sys_write():

        file = fget_light(fd, &fput_needed);
        if (file) {
                loff_t pos = file_pos_read(file);
                ret = vfs_write(file, buf, count, &pos);
                file_pos_write(file, pos);
                fput_light(file, fput_needed);
        }

Surely that's racy when two threads write to the same fd and the first
vfs_write call blocks or is preempted.  Or does fget_light take some
per-file lock that I'm not seeing?

             reply	other threads:[~2007-03-08 23:08 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-03-08 23:08 Michael K. Edwards [this message]
2007-03-08 23:43 ` sys_write() racy for multi-threaded append? Eric Dumazet
2007-03-08 23:57   ` Michael K. Edwards
2007-03-09  0:15     ` Eric Dumazet
2007-03-09  0:45       ` Michael K. Edwards
2007-03-09  1:34         ` Benjamin LaHaise
2007-03-09 12:19           ` Michael K. Edwards
2007-03-09 13:44             ` Eric Dumazet
2007-03-09 14:10             ` Alan Cox
2007-03-09 14:59             ` Benjamin LaHaise
2007-03-10  6:43               ` Michael K. Edwards
2007-03-09  5:53         ` Eric Dumazet
2007-03-09 11:52           ` Michael K. Edwards
2007-03-09  0:43 ` Alan Cox
     [not found] <7WzUo-1zl-21@gated-at.bofh.it>
     [not found] ` <7WAx2-2pg-21@gated-at.bofh.it>
     [not found]   ` <7WAGF-2Bx-9@gated-at.bofh.it>
     [not found]     ` <7WB07-3g5-33@gated-at.bofh.it>
     [not found]       ` <7WBt7-3SZ-23@gated-at.bofh.it>
2007-03-12  7:53         ` Bodo Eggert
2007-03-12 16:26           ` Michael K. Edwards
2007-03-12 18:48             ` Bodo Eggert
2007-03-13  0:46               ` Michael K. Edwards
2007-03-13  2:24                 ` Alan Cox
2007-03-13  7:25                   ` Michael K. Edwards
2007-03-13  7:42                     ` David Miller
2007-03-13 16:24                       ` Michael K. Edwards
2007-03-13 17:59                         ` Michael K. Edwards
2007-03-13 19:09                           ` Christoph Hellwig
2007-03-13 23:40                             ` Michael K. Edwards
2007-03-14  0:09                               ` Michael K. Edwards
2007-03-13 13:15                     ` Alan Cox
2007-03-14 20:09                       ` Michael K. Edwards
2007-03-16 16:43                         ` Frank Ch. Eigler
2007-03-16 17:25                         ` Alan Cox
2007-03-13 14:00                   ` David M. Lloyd

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