16895e4eac
commit 68514dacf2715d11b91ca50d88de047c086fea9c upstream.
A task can end up indefinitely sleeping in do_select() ->
poll_schedule_timeout() when the following race happens:
TASK1 (thread1) TASK2 TASK1 (thread2)
do_select()
setup poll_wqueues table
with 'fd'
write data to 'fd'
pollwake()
table->triggered = 1
closes 'fd' thread1 is
waiting for
poll_schedule_timeout()
- sees table->triggered
table->triggered = 0
return -EINTR
loop back in do_select()
But at this point when TASK1 loops back, the fdget() in the setup of
poll_wqueues fails. So now so we never find 'fd' is ready for reading
and sleep in poll_schedule_timeout() indefinitely.
Treat an fd that got closed as a fd on which some event happened. This
makes sure cannot block indefinitely in do_select().
Another option would be to return -EBADF in this case but that has a
potential of subtly breaking applications that excercise this behavior
and it happens to work for them. So returning fd as active seems like a
safer choice.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
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| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.