lkml.org 
[lkml]   [2021]   [Aug]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v3 0/5] Enable -Warray-bounds and -Wzero-length-bounds
    On Mon, Aug 30, 2021 at 11:44:54AM -0700, Nathan Chancellor wrote:
    > On Fri, Aug 27, 2021 at 09:30:10AM -0700, Kees Cook wrote:
    > > v3:
    > > - fix typo in treewide conversion (u8 should have been __u8)
    > > - improve changelog for DECLARE_FLEX_ARRAY patch
    > > - add acks/reviews
    > > v2: https://lore.kernel.org/lkml/20210826050458.1540622-1-keescook@chromium.org/
    > > v1: https://lore.kernel.org/lkml/20210818081118.1667663-1-keescook@chromium.org/
    > >
    > > Hi,
    > >
    > > In support of the improved buffer overflow detection for memcpy(),
    > > this enables -Warray-bounds and -Wzero-length-bounds globally. Mostly
    > > it involves some struct member tricks with the new DECLARE_FLEX_ARRAY()
    > > macro. Everything else is just replacing stacked 0-element arrays
    > > with actual unions in two related treewide patches. There is one set of
    > > special cases that were fixed separately[1] and are needed as well.
    > >
    > > I'm expecting to carry this series with the memcpy() series in my
    > > "overflow" tree. Reviews appreciated! :)
    >
    > Hi Kees,
    >
    > I ran this series through my local build tests and uncovered two
    > warnings in the same file that appear to be unhandled as of
    > next-20210830. This is from ARCH=powerpc pseries_defconfig with
    > clang-14, I did not try earlier versions of clang.

    Thanks for double-checking!

    >
    > arch/powerpc/kernel/signal_32.c:780:2: error: array index 3 is past the end of the array (which contains 1 element) [-Werror,-Warray-bounds]
    > unsafe_put_sigset_t(&frame->uc.uc_sigmask, oldset, failed);
    > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    > [...]
    > arch/powerpc/kernel/signal_32.c:1044:3: error: array index 2 is past the end of the array (which contains 1 element) [-Werror,-Warray-bounds]
    > unsafe_put_sigset_t(&old_ctx->uc_sigmask, &current->blocked, failed);
    > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    This smells like some kind of casting issue. uc_sigmask has only a single
    unsigned long element but unsafe_put_compat_sigset() seems to be doing
    stuff with [3], etc. Is it expecting u8? I will keep looking...

    --
    Kees Cook

    \
     
     \ /
      Last update: 2021-08-30 22:14    [W:4.359 / U:0.080 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site