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fec51d40ea
When an error occurs during a redirect we have two cases that need to be handled (i) we have a cork'ed buffer (ii) we have a normal sendmsg buffer. In the cork'ed buffer case we don't currently support recovering from errors in a redirect action. So the buffer is released and the error should _not_ be pushed back to the caller of sendmsg/sendpage. The rationale here is the user will get an error that relates to old data that may have been sent by some arbitrary thread on that sock. Instead we simple consume the data and tell the user that the data has been consumed. We may add proper error recovery in the future. However, this patch fixes a bug where the bytes outstanding counter sg_size was not zeroed. This could result in a case where if the user has both a cork'ed action and apply action in progress we may incorrectly call into the BPF program when the user expected an old verdict to be applied via the apply action. I don't have a use case where using apply and cork at the same time is valid but we never explicitly reject it because it should work fine. This patch ensures the sg_size is zeroed so we don't have this case. In the normal sendmsg buffer case (no cork data) we also do not zero sg_size. Again this can confuse the apply logic when the logic calls into the BPF program when the BPF programmer expected the old verdict to remain. So ensure we set sg_size to zero here as well. And additionally to keep the psock state in-sync with the sk_msg_buff release all the memory as well. Previously we did this before returning to the user but this left a gap where psock and sk_msg_buff states were out of sync which seems fragile. No additional overhead is taken here except for a call to check the length and realize its already been freed. This is in the error path as well so in my opinion lets have robust code over optimized error paths. Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.