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If a page sent into kernel_sendpage() is a slab page or it doesn't have ref_count, this page is improper to send by the zero copy sendpage() method. Otherwise such page might be unexpected released in network code path and causes impredictable panic due to kernel memory management data structure corruption. This path adds a WARN_ON() on the sending page before sends it into the concrete zero-copy sendpage() method, if the page is improper for the zero-copy sendpage() method, a warning message can be observed before the consequential unpredictable kernel panic. This patch does not change existing kernel_sendpage() behavior for the improper page zero-copy send, it just provides hint warning message for following potential panic due the kernel memory heap corruption. Signed-off-by: Coly Li <colyli@suse.de> Cc: Cong Wang <amwang@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: David S. Miller <davem@davemloft.net> Cc: Sridhar Samudrala <sri@us.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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.