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Alexander Lobakin 1463cd066f xsk: Harden userspace-supplied xdp_desc validation 
commit 07ca98f906 upstream.

Turned out certain clearly invalid values passed in xdp_desc from
userspace can pass xp_{,un}aligned_validate_desc() and then lead
to UBs or just invalid frames to be queued for xmit.

desc->len close to ``U32_MAX`` with a non-zero pool->tx_metadata_len
can cause positive integer overflow and wraparound, the same way low
enough desc->addr with a non-zero pool->tx_metadata_len can cause
negative integer overflow. Both scenarios can then pass the
validation successfully.
This doesn't happen with valid XSk applications, but can be used
to perform attacks.

Always promote desc->len to ``u64`` first to exclude positive
overflows of it. Use explicit check_{add,sub}_overflow() when
validating desc->addr (which is ``u64`` already).

bloat-o-meter reports a little growth of the code size:

add/remove: 0/0 grow/shrink: 2/1 up/down: 60/-16 (44)
Function                                     old     new   delta
xskq_cons_peek_desc                          299     330     +31
xsk_tx_peek_release_desc_batch               973    1002     +29
xsk_generic_xmit                            3148    3132     -16

but hopefully this doesn't hurt the performance much.

Fixes: 341ac980ea ("xsk: Support tx_metadata_len")
Cc: stable@vger.kernel.org # 6.8+
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/r/20251008165659.4141318-1-aleksander.lobakin@intel.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-10-19 16:33:53 +02:00
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README

README 

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 reStructuredText 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.