• Alexander Richardson's avatar
    dix/privates.c: Avoid undefined behaviour after realloc() · 22376023
    Alexander Richardson authored
    
    
    Adding the offset between the realloc result and the old allocation to
    update pointers into the new allocation is undefined behaviour: the
    old pointers are no longer valid after realloc() according to the C
    standard. While this works on almost all architectures and compilers,
    it causes  problems on architectures that track pointer bounds (e.g.
    CHERI or Arm's Morello): the DevPrivateKey pointers will still have the
    bounds of the previous allocation and therefore any dereference will
    result in a run-time trap.
    
    I found this due to a crash (dereferencing an invalid capability) while
    trying to run `XVnc` on a CHERI-RISC-V system. With this commit I can
    successfully connect to the XVnc instance running inside a QEMU with a
    VNC viewer on my host.
    Signed-off-by: Alexander Richardson's avatarAlex Richardson <Alexander.Richardson@cl.cam.ac.uk>
    22376023
privates.c 22.5 KB