• Mathieu Desnoyers's avatar
    Fix: compat_rw_copy_check_uvector() misuse in aio, readv, writev, and security keys · 8aec0f5d
    Mathieu Desnoyers authored
    Looking at mm/process_vm_access.c:process_vm_rw() and comparing it to
    compat_process_vm_rw() shows that the compatibility code requires an
    explicit "access_ok()" check before calling
    compat_rw_copy_check_uvector(). The same difference seems to appear when
    we compare fs/read_write.c:do_readv_writev() to
    This subtle difference between the compat and non-compat requirements
    should probably be debated, as it seems to be error-prone. In fact,
    there are two others sites that use this function in the Linux kernel,
    and they both seem to get it wrong:
    Now shifting our attention to fs/aio.c, we see that aio_setup_iocb()
    also ends up calling compat_rw_copy_check_uvector() through
    aio_setup_vectored_rw(). Unfortunately, the access_ok() check appears to
    be missing. Same situation for
    I propose that we add the access_ok() check directly into
    compat_rw_copy_check_uvector(), so callers don't have to worry about it,
    and it therefore makes the compat call code similar to its non-compat
    counterpart. Place the access_ok() check in the same location where
    copy_from_user() can trigger a -EFAULT error in the non-compat code, so
    the ABI behaviors are alike on both compat and non-compat.
    While we are here, fix compat_do_readv_writev() so it checks for
    compat_rw_copy_check_uvector() negative return values.
    And also, fix a memory leak in compat_keyctl_instantiate_key_iov() error
    Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    Acked-by: default avatarAl Viro <viro@ZenIV.linux.org.uk>
    Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
process_vm_access.c 13.2 KB