From: Petr Oros Date: Fri, 24 Oct 2025 13:24:38 +0000 (+0200) Subject: tools: ynl: fix string attribute length to include null terminator X-Git-Tag: v6.18-rc4~24^2~28 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=65f9c4c5888913c2cf5d2fc9454c83f9930d537d;p=thirdparty%2Flinux.git tools: ynl: fix string attribute length to include null terminator 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 Tested-by: Ivan Vecera Reviewed-by: Ivan Vecera Link: https://lore.kernel.org/20251018151737.365485-3-zahari.doychev@linux.com Link: https://patch.msgid.link/20251024132438.351290-1-poros@redhat.com Signed-off-by: Jakub Kicinski --- diff --git a/tools/net/ynl/lib/ynl-priv.h b/tools/net/ynl/lib/ynl-priv.h index 29481989ea76..ced7dce44efb 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); }