CVE-2024-27414

In the Linux kernel, the following vulnerability has been resolved:
rtnetlink: fix error logic of IFLA_BRIDGE_FLAGS writing back In the commit
d73ef2d69c0d (“rtnetlink: let rtnl_bridge_setlink checks IFLA_BRIDGE_MODE
length”), an adjustment was made to the old loop logic in the function
rtnl_bridge_setlink to enable the loop to also check the length of the
IFLA_BRIDGE_MODE attribute. However, this adjustment removed the break
statement and led to an error logic of the flags writing back at the end of
this function. if (have_flags) memcpy(nla_data(attr), &flags,
sizeof(flags)); // attr should point to IFLA_BRIDGE_FLAGS NLA !!! Before
the mentioned commit, the attr is granted to be IFLA_BRIDGE_FLAGS.
However, this is not necessarily true fow now as the updated loop will let
the attr point to the last NLA, even an invalid NLA which could cause
overflow writes. This patch introduces a new variable br_flag to save the
NLA pointer that points to IFLA_BRIDGE_FLAGS and uses it to resolve the
mentioned error logic.