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Kumar Kartikeya Dwivedi 2459615a8d bpf: Do mark_chain_precision for ARG_CONST_ALLOC_SIZE_OR_ZERO 
[ Upstream commit 2fc31465c5 ]

Precision markers need to be propagated whenever we have an ARG_CONST_*
style argument, as the verifier cannot consider imprecise scalars to be
equivalent for the purposes of states_equal check when such arguments
refine the return value (in this case, set mem_size for PTR_TO_MEM). The
resultant mem_size for the R0 is derived from the constant value, and if
the verifier incorrectly prunes states considering them equivalent where
such arguments exist (by seeing that both registers have reg->precise as
false in regsafe), we can end up with invalid programs passing the
verifier which can do access beyond what should have been the correct
mem_size in that explored state.

To show a concrete example of the problem:

0000000000000000 <prog>:
       0:       r2 = *(u32 *)(r1 + 80)
       1:       r1 = *(u32 *)(r1 + 76)
       2:       r3 = r1
       3:       r3 += 4
       4:       if r3 > r2 goto +18 <LBB5_5>
       5:       w2 = 0
       6:       *(u32 *)(r1 + 0) = r2
       7:       r1 = *(u32 *)(r1 + 0)
       8:       r2 = 1
       9:       if w1 == 0 goto +1 <LBB5_3>
      10:       r2 = -1

0000000000000058 <LBB5_3>:
      11:       r1 = 0 ll
      13:       r3 = 0
      14:       call bpf_ringbuf_reserve
      15:       if r0 == 0 goto +7 <LBB5_5>
      16:       r1 = r0
      17:       r1 += 16777215
      18:       w2 = 0
      19:       *(u8 *)(r1 + 0) = r2
      20:       r1 = r0
      21:       r2 = 0
      22:       call bpf_ringbuf_submit

00000000000000b8 <LBB5_5>:
      23:       w0 = 0
      24:       exit

For the first case, the single line execution's exploration will prune
the search at insn 14 for the branch insn 9's second leg as it will be
verified first using r2 = -1 (UINT_MAX), while as w1 at insn 9 will
always be 0 so at runtime we don't get error for being greater than
UINT_MAX/4 from bpf_ringbuf_reserve. The verifier during regsafe just
sees reg->precise as false for both r2 registers in both states, hence
considers them equal for purposes of states_equal.

If we propagated precise markers using the backtracking support, we
would use the precise marking to then ensure that old r2 (UINT_MAX) was
within the new r2 (1) and this would never be true, so the verification
would rightfully fail.

The end result is that the out of bounds access at instruction 19 would
be permitted without this fix.

Note that reg->precise is always set to true when user does not have
CAP_BPF (or when subprog count is greater than 1 (i.e. use of any static
or global functions)), hence this is only a problem when precision marks
need to be explicitly propagated (i.e. privileged users with CAP_BPF).

A simplified test case has been included in the next patch to prevent
future regressions.

Fixes: 457f44363a ("bpf: Implement BPF ring buffer and verifier support for it")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220823185300.406-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2022-09-08 11:23:58 +02:00
arch arm64: cacheinfo: Fix incorrect assignment of signed error value to unsigned fw_level 2022-09-05 10:31:36 +02:00
block blk-mq: fix io hung due to missing commit_rqs 2022-08-31 17:18:19 +02:00
certs certs: make system keyring depend on x509 parser 2022-07-24 12:53:55 -07:00
crypto KEYS: asymmetric: enforce SM2 signature use pkey algo 2022-08-17 15:16:17 +02:00
Documentation rtla: Fix tracer name 2022-09-05 10:31:31 +02:00
drivers Revert "xhci: turn off port power in shutdown" 2022-09-08 11:23:58 +02:00
fs btrfs: tree-checker: check for overlapping extent items 2022-09-05 10:31:35 +02:00
include bpf: Allow helpers to accept pointers with a fixed size 2022-09-08 11:23:58 +02:00
init arm64: fix rodata=full 2022-08-31 17:18:19 +02:00
io_uring io_uring: fix issue with io_write() not always undoing sb_start_write() 2022-08-31 17:18:17 +02:00
ipc ipc: Free mq_sysctls if ipc namespace creation failed 2022-06-22 17:47:41 -05:00
kernel bpf: Do mark_chain_precision for ARG_CONST_ALLOC_SIZE_OR_ZERO 2022-09-08 11:23:58 +02:00
lib crypto: lib - remove unneeded selection of XOR_BLOCKS 2022-09-05 10:31:26 +02:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm/rmap: Fix anon_vma->degree ambiguity leading to double-reuse 2022-09-05 10:31:28 +02:00
net wifi: cfg80211: debugfs: fix return type in ht40allow_map_read() 2022-09-08 11:23:58 +02:00
samples sample: bpf: xdp_router_ipv4: Allow the kernel to send arp requests 2022-08-17 15:14:25 +02:00
scripts kbuild: dummy-tools: avoid tmpdir leak in dummy gcc 2022-08-29 11:07:58 +02:00
security apparmor: Fix memleak in aa_simple_write_to_buffer() 2022-08-25 11:45:11 +02:00
sound ALSA: hda: intel-nhlt: Correct the handling of fmt_config flexible array 2022-09-08 11:23:58 +02:00
tools testing: selftests: nft_flowtable.sh: use random netns names 2022-09-05 10:31:35 +02:00
usr Not a lot of material this cycle. Many singleton patches against various 2022-05-27 11:22:03 -07:00
virt KVM: Unconditionally get a ref to /dev/kvm module when creating a VM 2022-08-25 11:45:05 +02:00
.clang-format clang-format: Fix space after for_each macros 2022-05-20 19:27:16 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 kbuild: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap ARM: SoC fixes for 5.19, part 4 2022-07-27 09:43:07 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ARM/PALM TREO SUPPORT orphan 2022-07-07 15:17:00 +02:00
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 io_uring: move to separate directory 2022-08-17 15:14:20 +02:00
Makefile Linux 5.19.7 2022-09-05 10:31:36 +02:00
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.