The ynl_attr_put_str() function was not including the null terminator in the attribute length calculation. This caused kernel to reject CTRL_CMD_GETFAMILY requests with EINVAL: "Attribute failed policy validation". For a 4-character family name like "dpll": - Sent: nla_len=8 (4 byte header + 4 byte string without null) - Expected: nla_len=9 (4 byte header + 5 byte string with null) The bug was introduced in commit 15d2540e0d62 ("tools: ynl: check for overflow of constructed messages") when refactoring from stpcpy() to strlen(). The original code correctly included the null terminator: end = stpcpy(ynl_attr_data(attr), str); attr->nla_len = NLA_HDRLEN + NLA_ALIGN(end - (char *)ynl_attr_data(attr)); Since stpcpy() returns a pointer past the null terminator, the length included it. The refactored version using strlen() omitted the +1. The fix also removes NLA_ALIGN() from nla_len calculation, since nla_len should contain actual attribute length, not aligned length. Alignment is only for calculating next attribute position. This makes the code consistent with ynl_attr_put(). CTRL_ATTR_FAMILY_NAME uses NLA_NUL_STRING policy which requires null terminator. Kernel validates with memchr() and rejects if not found. Fixes: 15d2540e0d62 ("tools: ynl: check for overflow of constructed messages") Signed-off-by: Petr Oros --- tools/net/ynl/lib/ynl-priv.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/net/ynl/lib/ynl-priv.h b/tools/net/ynl/lib/ynl-priv.h index 29481989ea7662..ced7dce44efb43 100644 --- a/tools/net/ynl/lib/ynl-priv.h +++ b/tools/net/ynl/lib/ynl-priv.h @@ -313,7 +313,7 @@ ynl_attr_put_str(struct nlmsghdr *nlh, unsigned int attr_type, const char *str) struct nlattr *attr; size_t len; - len = strlen(str); + len = strlen(str) + 1; if (__ynl_attr_put_overflow(nlh, len)) return; @@ -321,7 +321,7 @@ ynl_attr_put_str(struct nlmsghdr *nlh, unsigned int attr_type, const char *str) attr->nla_type = attr_type; strcpy((char *)ynl_attr_data(attr), str); - attr->nla_len = NLA_HDRLEN + NLA_ALIGN(len); + attr->nla_len = NLA_HDRLEN + len; nlh->nlmsg_len += NLMSG_ALIGN(attr->nla_len); } -- 2.51.0