ethtool: Fix and simplify ethtool_convert_link_mode_to_legacy_u32()

Fix the implementation of ethtool_convert_link_mode_to_legacy_u32(), which
is supposed to return false if src has bits higher than 31 set. The current
implementation uses the complement of bitmap_fill(ext, 32) to test high
bits of src, which is wrong as bitmap_fill() fills _with long granularity_,
and sizeof(long) can be > 4. No users of this function currently check the
return value, so the bug was dormant.

Also remove the check for __ETHTOOL_LINK_MODE_MASK_NBITS > 32, as the enum
ethtool_link_mode_bit_indices contains far beyond 32 values. Using
find_next_bit() to test the src bitmask works regardless of this anyway.

Signed-off-by: Marco Bonelli <marco@mebeim.net>
Link: https://lore.kernel.org/r/20220609134900.11201-1-marco@mebeim.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index d05ff6a17a1f80ce7205b1ae3973c761ca03d5c8..6a7308de192d90fba124d360818a58d2b310a959 100644 (file)
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -369,22 +369,9 @@ EXPORT_SYMBOL(ethtool_convert_legacy_u32_to_link_mode);
 bool ethtool_convert_link_mode_to_legacy_u32(u32 *legacy_u32,
                                             const unsigned long *src)
 {
-       bool retval = true;
-
-       /* TODO: following test will soon always be true */
-       if (__ETHTOOL_LINK_MODE_MASK_NBITS > 32) {
-               __ETHTOOL_DECLARE_LINK_MODE_MASK(ext);
-
-               linkmode_zero(ext);
-               bitmap_fill(ext, 32);
-               bitmap_complement(ext, ext, __ETHTOOL_LINK_MODE_MASK_NBITS);
-               if (linkmode_intersects(ext, src)) {
-                       /* src mask goes beyond bit 31 */
-                       retval = false;
-               }
-       }
        *legacy_u32 = src[0];
-       return retval;
+       return find_next_bit(src, __ETHTOOL_LINK_MODE_MASK_NBITS, 32) ==
+               __ETHTOOL_LINK_MODE_MASK_NBITS;
 }
 EXPORT_SYMBOL(ethtool_convert_link_mode_to_legacy_u32);