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selftests/bpf: ptr_to_btf_id struct walk ending with primitive pointer

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Validate that reading a PTR_TO_BTF_ID field produces a value of type
PTR_TO_MEM|MEM_RDONLY|PTR_UNTRUSTED, if field is a pointer to a
primitive type.

Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250704230354.1323244-4-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman 2025-07-04 16:03:49 -07:00 committed by Alexei Starovoitov
parent 2d5c91e1cc
commit f1f5d6f25d
1 changed files with 31 additions and 0 deletions
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31
tools/testing/selftests/bpf/progs/mem_rdonly_untrusted.c
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@ -5,6 +5,37 @@
#include "bpf_misc.h"
#include "../test_kmods/bpf_testmod_kfunc.h"
SEC("tp_btf/sys_enter")
__success
__log_level(2)
__msg("r8 = *(u64 *)(r7 +0) ; R7_w=ptr_nameidata(off={{[0-9]+}}) R8_w=rdonly_untrusted_mem(sz=0)")
__msg("r9 = *(u8 *)(r8 +0) ; R8_w=rdonly_untrusted_mem(sz=0) R9_w=scalar")
int btf_id_to_ptr_mem(void *ctx)
{
struct task_struct *task;
struct nameidata *idata;
u64 ret, off;
task = bpf_get_current_task_btf();
idata = task->nameidata;
off = bpf_core_field_offset(struct nameidata, pathname);
/*
* asm block to have reliable match target for __msg, equivalent of:
* ret = task->nameidata->pathname[0];
*/
asm volatile (
"r7 = %[idata];"
"r7 += %[off];"
"r8 = *(u64 *)(r7 + 0);"
"r9 = *(u8 *)(r8 + 0);"
"%[ret] = r9;"
: [ret]"=r"(ret)
: [idata]"r"(idata),
[off]"r"(off)
: "r7", "r8", "r9");
return ret;
}
SEC("socket")
__success
__retval(0)