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Filename Latest commit message Latest commit date
Piotr Krysiuk 6cce305480 bpf, x86: Validate computation of branch displacements for x86-32
commit 26f55a59dc65ff77cd1c4b37991e26497fc68049 upstream.

The branch displacement logic in the BPF JIT compilers for x86 assumes
that, for any generated branch instruction, the distance cannot
increase between optimization passes.

But this assumption can be violated due to how the distances are
computed. Specifically, whenever a backward branch is processed in
do_jit(), the distance is computed by subtracting the positions in the
machine code from different optimization passes. This is because part
of addrs[] is already updated for the current optimization pass, before
the branch instruction is visited.

And so the optimizer can expand blocks of machine code in some cases.

This can confuse the optimizer logic, where it assumes that a fixed
point has been reached for all machine code blocks once the total
program size stops changing. And then the JIT compiler can output
abnormal machine code containing incorrect branch displacements.

To mitigate this issue, we assert that a fixed point is reached while
populating the output image. This rejects any problematic programs.
The issue affects both x86-32 and x86-64. We mitigate separately to
ease backporting.

Signed-off-by: Piotr Krysiuk <piotras@gmail.com>
Reviewed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-04-10 13:34:31 +02:00
arch bpf, x86: Validate computation of branch displacements for x86-32 2021-04-10 13:34:31 +02:00
block
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drivers scsi: target: pscsi: Clean up after failure in pscsi_map_sg() 2021-04-10 13:34:31 +02:00
fs cifs: Silently ignore unknown oplock break handle 2021-04-10 13:34:31 +02:00
include extcon: Add stubs for extcon_register_notifier_all() functions 2021-04-07 14:47:43 +02:00
init
ipc
kernel tracing: Fix stack trace event size 2021-04-07 14:47:42 +02:00
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mm mm: fix race by making init_zero_pfn() early_initcall 2021-04-07 14:47:42 +02:00
net netfilter: conntrack: Fix gre tunneling over ipv6 2021-04-10 13:34:31 +02:00
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Makefile Linux 5.4.110 2021-04-07 14:47:45 +02:00
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 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.