libbpf: Clean up ringbuf size adjustment implementation

Drop unused iteration variable, move overflow prevention check into the
for loop.

Fixes: 0087a681fa8c ("libbpf: Automatically fix up BPF_MAP_TYPE_RINGBUF size, if necessary")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220510185159.754299-1-andrii@kernel.org

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index a5904c0ac7940e8832fe0258e2d0ac0a41d6cecd..0e74fae2589623b9b809895be1471e777cb9dcae 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4951,7 +4951,7 @@ static bool is_pow_of_2(size_t x)
 static size_t adjust_ringbuf_sz(size_t sz)
 {
        __u32 page_sz = sysconf(_SC_PAGE_SIZE);
-       __u32 i, mul;
+       __u32 mul;
 
        /* if user forgot to set any size, make sure they see error */
        if (sz == 0)
@@ -4967,9 +4967,7 @@ static size_t adjust_ringbuf_sz(size_t sz)
         * user-set size to satisfy both user size request and kernel
         * requirements and substitute correct max_entries for map creation.
         */
-       for (i = 0, mul = 1; ; i++, mul <<= 1) {
-               if (mul > UINT_MAX / page_sz) /* prevent __u32 overflow */
-                       break;
+       for (mul = 1; mul <= UINT_MAX / page_sz; mul <<= 1) {
                if (mul * page_sz > sz)
                        return mul * page_sz;
        }