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Merge branch 'bpf-additional-use-cases-for-untrusted-ptr_to_mem'
Eduard Zingerman says:
====================
bpf: additional use-cases for untrusted PTR_TO_MEM
This patch set introduces two usability enhancements leveraging
untrusted pointers to mem:
- When reading a pointer field from a PTR_TO_BTF_ID, the resulting
value is now assumed to be PTR_TO_MEM|MEM_RDONLY|PTR_UNTRUSTED
instead of SCALAR_VALUE, provided the pointer points to a primitive
type.
- __arg_untrusted attribute for global function parameters,
allowed for pointer arguments of both structural and primitive
types:
- For structural types, the attribute produces
PTR_TO_BTF_ID|PTR_UNTRUSTED.
- For primitive types, it yields
PTR_TO_MEM|MEM_RDONLY|PTR_UNTRUSTED.
Here are examples enabled by the series:
struct foo {
int *arr;
};
...
p = bpf_core_cast(..., struct foo);
bpf_for(i, 0, ...) {
... p->arr[i] ... // load at any offset is allowed
}
int memcmp(void *a __arg_untrusted, void *b __arg_untrusted, size_t n) {
bpf_for(i, 0, n)
if (a[i] - b[i]) // load at any offset is allowed
return ...;
return 0;
}
The patch-set was inspired by Anrii's series [1]. The goal of that
series was to define a generic global glob_match function, capable to
accept any pointer type:
__weak int glob_match(const char *pat, const char *str);
char filename_glob[32];
void foo(...) {
...
task = bpf_get_current_task_btf();
filename = task->mm->exe_file->f_path.dentry->d_name.name;
... match_glob(filename_glob, // pointer to map value
filename) ... // scalar
}
At the moment, there is no straightforward way to express such a
function. This patch-set makes it possible to define it as follows:
__weak int glob_match(const char *pat __arg_untrusted,
const char *str __arg_untrusted);
[1] https://github.com/anakryiko/linux/tree/bpf-mem-cast
Changelog:
v1: https://lore.kernel.org/bpf/20250702224209.3300396-1-eddyz87@gmail.com/
v1 -> v2:
- Added safety check in btf_prepare_func_args() to ensure that only
struct or primitive types could be combined with __arg_untrusted
(Alexei).
- Removed unnecessary 'continue' btf_check_func_arg_match() (Alexei).
- Added test cases for __arg_untrusted pointers to enum and
__arg_untrusted combined with non-kernel type (Kumar).
- Added acks from Kumar.
====================
Link: https://patch.msgid.link/20250704230354.1323244-1-eddyz87@gmail.com
Signed-off-by: 
Alexei Starovoitov <ast@kernel.org>