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selftests/bpf: Use bpf_dynptr_slice() to read file dynptr in leak test

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use_file_dynptr_slice_after_put_file() reads the dynptr via
bpf_dynptr_data(), which always returns NULL for a read-only file
dynptr, making the example confusing. Switch to bpf_dynptr_slice(), the
correct read API for file dynptrs, and read (rather than write) the slice
since it is read-only. The test still fails as expected.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260605202056.1780352-6-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Amery Hung 2026-06-05 13:20:56 -07:00 committed by Alexei Starovoitov
parent ac7f6c9da6
commit d83d4f63cb
1 changed files with 4 additions and 4 deletions
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8
tools/testing/selftests/bpf/progs/file_reader_fail.c
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@ -87,7 +87,8 @@ 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;
char buf[1];
const char *data;
if (!file)
return 0;
@ -95,15 +96,14 @@ int use_file_dynptr_slice_after_put_file(void *ctx)
if (bpf_dynptr_from_file(file, 0, &dynptr))
goto out;
data = bpf_dynptr_data(&dynptr, 0, 1);
data = bpf_dynptr_slice(&dynptr, 0, buf, sizeof(buf));
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;
return data[0];
out:
bpf_dynptr_file_discard(&dynptr);