0adf21eec5
commit 353f7988dd8413c47718f7ca79c030b6fb62cfe5 upstream. When the pipe is closed, we mark the associated watchqueue defunct by calling watch_queue_clear(). However, while that is protected by the watchqueue lock, new watchqueue entries aren't actually added under that lock at all: they use the pipe->rd_wait.lock instead, and looking up that pipe happens without any locking. The watchqueue code uses the RCU read-side section to make sure that the wqueue entry itself hasn't disappeared, but that does not protect the pipe_info in any way. So make sure to actually hold the wqueue lock when posting watch events, properly serializing against the pipe being torn down. Reported-by: Noam Rathaus <noamr@ssd-disclosure.com> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.