683916f6a8
sk_msg_trim() tries to only update curr pointer if it falls into the trimmed region. The logic, however, does not take into the account pointer wrapping that sk_msg_iter_var_prev() does nor (as John points out) the fact that msg->sg is a ring buffer. This means that when the message was trimmed completely, the new curr pointer would have the value of MAX_MSG_FRAGS - 1, which is neither smaller than any other value, nor would it actually be correct. Special case the trimming to 0 length a little bit and rework the comparison between curr and end to take into account wrapping. This bug caused the TLS code to not copy all of the message, if zero copy filled in fewer sg entries than memcopy would need. Big thanks to Alexander Potapenko for the non-KMSAN reproducer. v2: - take into account that msg->sg is a ring buffer (John). Link: https://lore.kernel.org/netdev/20191030160542.30295-1-jakub.kicinski@netronome.com/ (v1) Fixes: d829e9c4112b ("tls: convert to generic sk_msg interface") Reported-by: syzbot+f8495bff23a879a6d0bd@syzkaller.appspotmail.com Reported-by: syzbot+6f50c99e8f6194bf363f@syzkaller.appspotmail.com Co-developed-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Signed-off-by: John Fastabend <john.fastabend@gmail.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.