mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-07 20:58:14 -04:00
6f5d82806b
Arseniy Krasnov says: ==================== fix header length on skb merging this patchset fixes appending newly arrived skbuff to the last skbuff of the socket's queue during rx path. Problem fires when we are trying to append data to skbuff which was already processed in dequeue callback at least once. Dequeue callback calls function 'skb_pull()' which changes 'skb->len'. In current implementation 'skb->len' is used to update length in header of last skbuff after new data was copied to it. This is bug, because value in header is used to calculate 'rx_bytes'/'fwd_cnt' and thus must be constant during skbuff lifetime. Here is example, we have two skbuffs: skb0 with length 10 and skb1 with length 4. 1) skb0 arrives, hdr->len == skb->len == 10, rx_bytes == 10 2) Read 3 bytes from skb0, skb->len == 7, hdr->len == 10, rx_bytes == 10 3) skb1 arrives, hdr->len == skb->len == 4, rx_bytes == 14 4) Append skb1 to skb0, skb0 now has skb->len == 11, hdr->len == 11. But value of 11 in header is invalid. 5) Read whole skb0, update rx_bytes by 11 from skb0's header. 6) At this moment rx_bytes == 3, but socket's queue is empty. This bug starts to fire since: commit0777061657("virtio/vsock: don't use skbuff state to account credit") In fact, it presents before, but didn't triggered due to a little bit buggy implementation of credit calculation logic. So i'll use Fixes tag for it. I really forgot about this branch in rx path when implemented patch0777061657. This patchset contains 3 patches: 1) Fix itself. 2) Patch with WARN_ONCE() to catch such problems in future. 3) Patch with test which triggers skb appending logic. It looks like simple test with several 'send()' and 'recv()', but it checks, that skbuff appending works ok. ==================== Link: https://lore.kernel.org/r/0683cc6e-5130-484c-1105-ef2eb792d355@sberdevices.ru Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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.