lkml.org 
[lkml]   [2023]   [Mar]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH] kheaders: Use array declaration instead of char
    Date
    Under CONFIG_FORTIFY_SOURCE, memcpy() will check the size of destination
    and source buffers. Defining kernel_headers_data as "char" would trip
    this check. Since these addresses are treated as byte arrays, define
    them as arrays (as done everywhere else).

    This was seen with:

    $ cat /sys/kernel/kheaders.tar.xz >> /dev/null

    detected buffer overflow in memcpy
    kernel BUG at lib/string_helpers.c:1027!
    ...
    RIP: 0010:fortify_panic+0xf/0x20
    [...]
    Call Trace:
    <TASK>
    ikheaders_read+0x45/0x50 [kheaders]
    kernfs_fop_read_iter+0x1a4/0x2f0
    ...

    Reported-by: Jakub Kicinski <kuba@kernel.org>
    Link: https://lore.kernel.org/bpf/20230302112130.6e402a98@kernel.org/
    Tested-by: Jakub Kicinski <kuba@kernel.org>
    Fixes: 43d8ce9d65a5 ("Provide in-kernel headers to make extending kernel easier")
    Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
    Cc: stable@vger.kernel.org
    Signed-off-by: Kees Cook <keescook@chromium.org>
    ---
    kernel/kheaders.c | 10 +++++-----
    1 file changed, 5 insertions(+), 5 deletions(-)

    diff --git a/kernel/kheaders.c b/kernel/kheaders.c
    index 8f69772af77b..42163c9e94e5 100644
    --- a/kernel/kheaders.c
    +++ b/kernel/kheaders.c
    @@ -26,15 +26,15 @@ asm (
    " .popsection \n"
    );

    -extern char kernel_headers_data;
    -extern char kernel_headers_data_end;
    +extern char kernel_headers_data[];
    +extern char kernel_headers_data_end[];

    static ssize_t
    ikheaders_read(struct file *file, struct kobject *kobj,
    struct bin_attribute *bin_attr,
    char *buf, loff_t off, size_t len)
    {
    - memcpy(buf, &kernel_headers_data + off, len);
    + memcpy(buf, &kernel_headers_data[off], len);
    return len;
    }

    @@ -48,8 +48,8 @@ static struct bin_attribute kheaders_attr __ro_after_init = {

    static int __init ikheaders_init(void)
    {
    - kheaders_attr.size = (&kernel_headers_data_end -
    - &kernel_headers_data);
    + kheaders_attr.size = (kernel_headers_data_end -
    + kernel_headers_data);
    return sysfs_create_bin_file(kernel_kobj, &kheaders_attr);
    }

    --
    2.34.1
    \
     
     \ /
      Last update: 2023-03-27 00:42    [W:4.416 / U:0.448 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site