lkml.org 
[lkml]   [2017]   [Jul]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH] lib/strscpy: avoid KASAN false positive
    Date
    strscpy() performs the word-at-a-time optimistic reads. So it may
    may access the memory past the end of the object, which is perfectly fine
    since strscpy() doesn't use that (past-the-end) data and makes sure the
    optimistic read won't cross a page boundary.

    But KASAN doesn't know anything about that so it will complain.
    Let's just fallback to the byte-at-a-time reads under CONFIG_KASAN=y
    to avoid false-positives.

    Reported-by: Dave Jones <davej@codemonkey.org.uk>
    Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
    ---
    lib/string.c | 7 +++++++
    1 file changed, 7 insertions(+)

    diff --git a/lib/string.c b/lib/string.c
    index ebbb99c775bd..8b93d2519d5a 100644
    --- a/lib/string.c
    +++ b/lib/string.c
    @@ -199,6 +199,13 @@ ssize_t strscpy(char *dest, const char *src, size_t count)
    max = 0;
    #endif

    + /*
    + * KASAN won't be happy about word-at-a-time
    + * optimistic reads, so let's avoid them.
    + */
    + if (IS_ENABLED(CONFIG_KASAN))
    + max = 0;
    +
    while (max >= sizeof(unsigned long)) {
    unsigned long c, data;

    --
    2.13.0
    \
     
     \ /
      Last update: 2017-07-18 19:14    [W:3.308 / U:0.616 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site