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selftests/bpf: Add test for truncated dmabuf_iter reads

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If many dmabufs are present, reads of the dmabuf iterator can be
truncated at PAGE_SIZE or user buffer size boundaries before the fix in
"bpf: Fix truncated dmabuf iterator reads". Add a test to
confirm truncation does not occur.

Signed-off-by: T.J. Mercier <tjmercier@google.com>
Link: https://lore.kernel.org/r/20251204000348.1413593-2-tjmercier@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
T.J. Mercier 2025-12-03 16:03:48 -08:00 committed by Alexei Starovoitov
parent 234483565d
commit 9489d457d4
1 changed files with 42 additions and 5 deletions
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47
tools/testing/selftests/bpf/prog_tests/dmabuf_iter.c
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@ -73,12 +73,10 @@ close_memfd:
return -1;
}
static int create_sys_heap_dmabuf(void)
static int create_sys_heap_dmabuf(size_t bytes)
{
sysheap_test_buffer_size = 20 * getpagesize();
struct dma_heap_allocation_data data = {
.len = sysheap_test_buffer_size,
.len = bytes,
.fd = 0,
.fd_flags = O_RDWR | O_CLOEXEC,
.heap_flags = 0,
@ -110,7 +108,9 @@ close_sysheap_dmabuf:
static int create_test_buffers(void)
{
udmabuf = create_udmabuf();
sysheap_dmabuf = create_sys_heap_dmabuf();
sysheap_test_buffer_size = 20 * getpagesize();
sysheap_dmabuf = create_sys_heap_dmabuf(sysheap_test_buffer_size);
if (udmabuf < 0 || sysheap_dmabuf < 0)
return -1;
@ -219,6 +219,26 @@ close_iter_fd:
close(iter_fd);
}
static void subtest_dmabuf_iter_check_lots_of_buffers(struct dmabuf_iter *skel)
{
int iter_fd;
char buf[1024];
size_t total_bytes_read = 0;
ssize_t bytes_read;
iter_fd = bpf_iter_create(bpf_link__fd(skel->links.dmabuf_collector));
if (!ASSERT_OK_FD(iter_fd, "iter_create"))
return;
while ((bytes_read = read(iter_fd, buf, sizeof(buf))) > 0)
total_bytes_read += bytes_read;
ASSERT_GT(total_bytes_read, getpagesize(), "total_bytes_read");
close(iter_fd);
}
static void subtest_dmabuf_iter_check_open_coded(struct dmabuf_iter *skel, int map_fd)
{
LIBBPF_OPTS(bpf_test_run_opts, topts);
@ -275,6 +295,23 @@ void test_dmabuf_iter(void)
subtest_dmabuf_iter_check_no_infinite_reads(skel);
if (test__start_subtest("default_iter"))
subtest_dmabuf_iter_check_default_iter(skel);
if (test__start_subtest("lots_of_buffers")) {
size_t NUM_BUFS = 100;
int buffers[NUM_BUFS];
int i;
for (i = 0; i < NUM_BUFS; ++i) {
buffers[i] = create_sys_heap_dmabuf(getpagesize());
if (!ASSERT_OK_FD(buffers[i], "dmabuf_fd"))
goto cleanup_bufs;
}
subtest_dmabuf_iter_check_lots_of_buffers(skel);
cleanup_bufs:
for (--i; i >= 0; --i)
close(buffers[i]);
}
if (test__start_subtest("open_coded"))
subtest_dmabuf_iter_check_open_coded(skel, map_fd);