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Dave Hansen 41d8b591d7 uaccess: Add speculation barrier to copy_from_user() 
commit 74e19ef0ff upstream.

The results of "access_ok()" can be mis-speculated.  The result is that
you can end speculatively:

	if (access_ok(from, size))
		// Right here

even for bad from/size combinations.  On first glance, it would be ideal
to just add a speculation barrier to "access_ok()" so that its results
can never be mis-speculated.

But there are lots of system calls just doing access_ok() via
"copy_to_user()" and friends (example: fstat() and friends).  Those are
generally not problematic because they do not _consume_ data from
userspace other than the pointer.  They are also very quick and common
system calls that should not be needlessly slowed down.

"copy_from_user()" on the other hand uses a user-controller pointer and
is frequently followed up with code that might affect caches.  Take
something like this:

	if (!copy_from_user(&kernelvar, uptr, size))
		do_something_with(kernelvar);

If userspace passes in an evil 'uptr' that *actually* points to a kernel
addresses, and then do_something_with() has cache (or other)
side-effects, it could allow userspace to infer kernel data values.

Add a barrier to the common copy_from_user() code to prevent
mis-speculated values which happen after the copy.

Also add a stub for architectures that do not define barrier_nospec().
This makes the macro usable in generic code.

Since the barrier is now usable in generic code, the x86 #ifdef in the
BPF code can also go away.

Reported-by: Jordy Zomer <jordyzomer@google.com>
Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>   # BPF bits
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-02-25 12:06:44 +01:00
arch powerpc/64s/radix: Fix RWX mapping with relocated kernel 2023-02-25 12:06:44 +01:00
block block, bfq: fix uaf for bfqq in bic_set_bfqq() 2023-02-09 11:26:36 +01:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: tcrypt - Fix multibuffer skcipher speed test mem leak 2022-12-31 13:14:24 +01:00
Documentation Documentation/hw-vuln: Add documentation for Cross-Thread Return Predictions 2023-02-14 19:18:05 +01:00
drivers drm/i915/gvt: fix double free bug in split_2MB_gtt_entry 2023-02-25 12:06:44 +01:00
fs nilfs2: fix underflow in second superblock position calculations 2023-02-22 12:57:10 +01:00
include uaccess: Add speculation barrier to copy_from_user() 2023-02-25 12:06:44 +01:00
init init/Kconfig: fix CC_HAS_ASM_GOTO_TIED_OUTPUT test with dash 2022-12-02 17:41:08 +01:00
io_uring io_uring/rw: remove leftover debug statement 2023-01-24 07:22:49 +01:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel uaccess: Add speculation barrier to copy_from_user() 2023-02-25 12:06:44 +01:00
lib uaccess: Add speculation barrier to copy_from_user() 2023-02-25 12:06:44 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm/filemap: fix page end in filemap_get_read_batch 2023-02-22 12:57:10 +01:00
net net: sched: sch: Fix off by one in htb_activate_prios() 2023-02-22 12:57:11 +01:00
samples samples: vfio-mdev: Fix missing pci_disable_device() in mdpy_fb_probe() 2022-12-31 13:14:31 +01:00
scripts kbuild: Allow kernel installation packaging to override pkg-config 2023-02-01 08:27:30 +01:00
security tomoyo: fix broken dependency on *.conf.default 2023-02-01 08:27:05 +01:00
sound ASoC: SOF: Intel: hda-dai: fix possible stream_tag leak 2023-02-22 12:57:11 +01:00
tools selftest/lkdtm: Skip stack-entropy test if lkdtm is not available 2023-02-22 12:57:07 +01:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt kvm: Add support for arch compat vm ioctls 2022-10-29 10:12:54 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS futex: Move to kernel/futex/ 2022-12-31 13:14:04 +01:00
Makefile Linux 5.15.95 2023-02-22 12:57:12 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.