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selftests/bpf: Test using file dynptr after the reference on file is dropped

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File dynptr and slice should be invalidated when the parent file's
reference is dropped in the program. Without the verifier tracking
dyntpr's parent referenced object, the dynptr would continute to be
incorrectly used even if the underlying file is being tear down or gone.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260529014936.2811085-13-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Amery Hung 2026-05-28 18:49:35 -07:00 committed by Alexei Starovoitov
parent 925320666e
commit 3f75a757a3
1 changed files with 60 additions and 0 deletions
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60
tools/testing/selftests/bpf/progs/file_reader_fail.c
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@ -50,3 +50,63 @@ int xdp_no_dynptr_type(struct xdp_md *xdp)
bpf_dynptr_file_discard(&dynptr);
return 0;
}
SEC("lsm/file_open")
__failure
__msg("Leaking reference id={{[0-9]+}} alloc_insn={{[0-9]+}}. Release it first.")
int use_file_dynptr_after_put_file(void *ctx)
{
struct task_struct *task = bpf_get_current_task_btf();
struct file *file = bpf_get_task_exe_file(task);
struct bpf_dynptr dynptr;
char buf[64];
if (!file)
return 0;
if (bpf_dynptr_from_file(file, 0, &dynptr))
goto out;
/* this should fail - file dynptr should be discarded first to prevent resource leak */
bpf_put_file(file);
bpf_dynptr_read(buf, sizeof(buf), &dynptr, 0, 0);
return 0;
out:
bpf_dynptr_file_discard(&dynptr);
bpf_put_file(file);
return 0;
}
SEC("lsm/file_open")
__failure
__msg("Leaking reference id={{[0-9]+}} alloc_insn={{[0-9]+}}. Release it first.")
int use_file_dynptr_slice_after_put_file(void *ctx)
{
struct task_struct *task = bpf_get_current_task_btf();
struct file *file = bpf_get_task_exe_file(task);
struct bpf_dynptr dynptr;
char *data;
if (!file)
return 0;
if (bpf_dynptr_from_file(file, 0, &dynptr))
goto out;
data = bpf_dynptr_data(&dynptr, 0, 1);
if (!data)
goto out;
/* this should fail - file dynptr should be discarded first to prevent resource leak */
bpf_put_file(file);
*data = 'x';
return 0;
out:
bpf_dynptr_file_discard(&dynptr);
bpf_put_file(file);
return 0;
}