Subject: CVE-2024-43910: bpf: add missing check_func_arg_reg_off() to prevent out-of-bounds memory accesses

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

bpf: add missing check_func_arg_reg_off() to prevent out-of-bounds memory accesses

Currently, it's possible to pass in a modified CONST_PTR_TO_DYNPTR to
a global function as an argument. The adverse effects of this is that
BPF helpers can continue to make use of this modified
CONST_PTR_TO_DYNPTR from within the context of the global function,
which can unintentionally result in out-of-bounds memory accesses and
therefore compromise overall system stability i.e.

[  244.157771] BUG: KASAN: slab-out-of-bounds in bpf_dynptr_data+0x137/0x140
[  244.161345] Read of size 8 at addr ffff88810914be68 by task test_progs/302
[  244.167151] CPU: 0 PID: 302 Comm: test_progs Tainted: G O E 6.10.0-rc3-00131-g66b586715063 #533
[  244.174318] Call Trace:
[  244.175787]  <TASK>
[  244.177356]  dump_stack_lvl+0x66/0xa0
[  244.179531]  print_report+0xce/0x670
[  244.182314]  ? __virt_addr_valid+0x200/0x3e0
[  244.184908]  kasan_report+0xd7/0x110
[  244.187408]  ? bpf_dynptr_data+0x137/0x140
[  244.189714]  ? bpf_dynptr_data+0x137/0x140
[  244.192020]  bpf_dynptr_data+0x137/0x140
[  244.194264]  bpf_prog_b02a02fdd2bdc5fa_global_call_bpf_dynptr_data+0x22/0x26
[  244.198044]  bpf_prog_b0fe7b9d7dc3abde_callback_adjust_bpf_dynptr_reg_off+0x1f/0x23
[  244.202136]  bpf_user_ringbuf_drain+0x2c7/0x570
[  244.204744]  ? 0xffffffffc0009e58
[  244.206593]  ? __pfx_bpf_user_ringbuf_drain+0x10/0x10
[  244.209795]  bpf_prog_33ab33f6a804ba2d_user_ringbuf_callback_const_ptr_to_dynptr_reg_off+0x47/0x4b
[  244.215922]  bpf_trampoline_6442502480+0x43/0xe3
[  244.218691]  __x64_sys_prlimit64+0x9/0xf0
[  244.220912]  do_syscall_64+0xc1/0x1d0
[  244.223043]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[  244.226458] RIP: 0033:0x7ffa3eb8f059
[  244.228582] Code: 08 89 e8 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 8f 1d 0d 00 f7 d8 64 89 01 48
[  244.241307] RSP: 002b:00007ffa3e9c6eb8 EFLAGS: 00000206 ORIG_RAX: 000000000000012e
[  244.246474] RAX: ffffffffffffffda RBX: 00007ffa3e9c7cdc RCX: 00007ffa3eb8f059
[  244.250478] RDX: 00007ffa3eb162b4 RSI: 0000000000000000 RDI: 00007ffa3e9c7fb0
[  244.255396] RBP: 00007ffa3e9c6ed0 R08: 00007ffa3e9c76c0 R09: 0000000000000000
[  244.260195] R10: 0000000000000000 R11: 0000000000000206 R12: ffffffffffffff80
[  244.264201] R13: 000000000000001c R14: 00007ffc5d6b4260 R15: 00007ffa3e1c7000
[  244.268303]  </TASK>

Add a check_func_arg_reg_off() to the path in which the BPF verifier
verifies the arguments of global function arguments, specifically
those which take an argument of type ARG_PTR_TO_DYNPTR |
MEM_RDONLY. Also, process_dynptr_func() doesn't appear to perform any
explicit and strict type matching on the supplied register type, so
let's also enforce that a register either type PTR_TO_STACK or
CONST_PTR_TO_DYNPTR is by the caller.

The Linux kernel CVE team has assigned CVE-2024-43910 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 6.8 with commit a64bfe618665 and fixed in 6.10.5 with commit 13663a7c644b
	Issue introduced in 6.8 with commit a64bfe618665 and fixed in 6.11 with commit ec2b9a5e11e5

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-43910
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	kernel/bpf/verifier.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/13663a7c644bf1dedaf461d07252db5d76c8759a
	https://git.kernel.org/stable/c/ec2b9a5e11e51fea1bb04c1e7e471952e887e874