In the Linux kernel, the following vulnerability has been resolved:
rtnetlink: fix error logic of IFLABRIDGEFLAGS writing back
In the commit d73ef2d69c0d ("rtnetlink: let rtnlbridgesetlink checks
IFLABRIDGEMODE 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 IFLABRIDGEMODE 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 (haveflags) memcpy(nladata(attr), &flags, sizeof(flags)); // attr should point to IFLABRIDGEFLAGS NLA !!!
Before the mentioned commit, the attr
is granted to be IFLABRIDGEFLAGS.
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 IFLABRIDGEFLAGS and uses it to resolve the mentioned
error logic.