CVE-2024-49861
Global infos:
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix helper writes to read-only maps
Lonial found an issue that despite user- and BPF-side frozen BPF map
(like in case of .rodata), it was still possible to write into it from
a BPF program side through specific helpers having ARG_PTR_TO_{LONG,INT}
as arguments.
In check_func_arg() when the argument is as mentioned, the meta->raw_mode
is never set. Later, check_helper_mem_access(), under the case of
PTR_TO_MAP_VALUE as register base type, it assumes BPF_READ for the
subsequent call to check_map_access_type() and given the BPF map is
read-only it succeeds.
The helpers really need to be annotated as ARG_PTR_TO_{LONG,INT} | MEM_UNINIT
when results are written into them as opposed to read out of them. The
latter indicates that it's okay to pass a pointer to uninitialized memory
as the memory is written to anyway.
However, ARG_PTR_TO_{LONG,INT} is a special case of ARG_PTR_TO_FIXED_SIZE_MEM
just with additional alignment requirement. So it is better to just get
rid of the ARG_PTR_TO_{LONG,INT} special cases altogether and reuse the
fixed size memory types. For this, add MEM_ALIGNED to additionally ensure
alignment given these helpers write directly into the args via *
CVE Status: Modified
References:
Metrics:
| Attribute | Value |
|---|---|
| Attack Complexity | LOW |
| Attack Vector | LOCAL |
| Availability Impact | HIGH |
| Base Score | 7.1 |
| Base Severity | HIGH |
| Confidentiality Impact | NONE |
| Integrity Impact | HIGH |
| Privileges Required | LOW |
| Scope | UNCHANGED |
| User Interaction | NONE |
| Vector String | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H |
| Exploitability Score | 1.8 |
| Impact Score | 5.2 |
| Source | [email protected] |
| Type | Primary |