CVE-2024-49861
bpf: Fix helper writes to read-only maps
We use these services and cookies to improve your user experience. You may opt out if you wish, however, this may limit some features on this site.
Please see our statement on Data Privacy.
bpf: Fix helper writes to read-only maps
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 *<ptr> = val. The .arg*_size has been initialized reflecting the actual sizeof(*<ptr>). MEM_ALIGNED can only be used in combination with MEM_FIXED_SIZE annotated argument types, since in !MEM_FIXED_SIZE cases the verifier does not know the buffer size a priori and therefore cannot blindly write *<ptr> = val.
Reserved 2024-10-21 | Published 2024-10-21 | Updated 2024-12-19 | Assigner Linuxgit.kernel.org/...c/988e55abcf7fdb8fc9a76a7cf3f4e939a4d4fb3a
git.kernel.org/...c/a2c8dc7e21803257e762b0bf067fd13e9c995da0
git.kernel.org/...c/2ed98ee02d1e08afee88f54baec39ea78dc8a23c
git.kernel.org/...c/1e75d25133158b525e0456876e9bcfd6b2993fd5
git.kernel.org/...c/32556ce93bc45c730829083cb60f95a2728ea48b
Support options
