Commit 41332d6e authored by Yuntao Wang's avatar Yuntao Wang Committed by Daniel Borkmann
Browse files

libbpf: Add a check to ensure that page_cnt is non-zero 



The page_cnt parameter is used to specify the number of memory pages
allocated for each per-CPU buffer, it must be non-zero and a power of 2.

Currently, the __perf_buffer__new() function attempts to validate that
the page_cnt is a power of 2 but forgets checking for the case where
page_cnt is zero, we can fix it by replacing 'page_cnt & (page_cnt - 1)'
with 'page_cnt == 0 || (page_cnt & (page_cnt - 1))'.

If so, we also don't need to add a check in perf_buffer__new_v0_6_0() to
make sure that page_cnt is non-zero and the check for zero in
perf_buffer__new_raw_v0_6_0() can also be removed.

The code will be cleaner and more readable.

Signed-off-by: default avatarYuntao Wang <ytcoode@gmail.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220303005921.53436-1-ytcoode@gmail.com
parent 8bbe98bd

tools/lib/bpf/libbpf.c

+2 −2
Original line number Diff line number Diff line
@@ -10951,7 +10951,7 @@ struct perf_buffer *perf_buffer__new_raw_v0_6_0(int map_fd, size_t page_cnt, 
{

	struct perf_buffer_params p = {};



	if (page_cnt == 0 || !attr)

	if (!attr)

		return libbpf_err_ptr(-EINVAL);



	if (!OPTS_VALID(opts, perf_buffer_raw_opts))
@@ -10992,7 +10992,7 @@ static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt, 
	__u32 map_info_len;

	int err, i, j, n;



	if (page_cnt & (page_cnt - 1)) {

	if (page_cnt == 0 || (page_cnt & (page_cnt - 1))) {

		pr_warn("page count should be power of two, but is %zu\n",

			page_cnt);

		return ERR_PTR(-EINVAL);