lkml.org 
[lkml]   [2014]   [Apr]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 3.11 34/46] netlink: don't compare the nul-termination in nla_strcmp
    Date
    3.11.10.8 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Pablo Neira <pablo@netfilter.org>

    commit 8b7b932434f5eee495b91a2804f5b64ebb2bc835 upstream.

    nla_strcmp compares the string length plus one, so it's implicitly
    including the nul-termination in the comparison.

    int nla_strcmp(const struct nlattr *nla, const char *str)
    {
    int len = strlen(str) + 1;
    ...
    d = memcmp(nla_data(nla), str, len);

    However, if NLA_STRING is used, userspace can send us a string without
    the nul-termination. This is a problem since the string
    comparison will not match as the last byte may be not the
    nul-termination.

    Fix this by skipping the comparison of the nul-termination if the
    attribute data is nul-terminated. Suggested by Thomas Graf.

    Cc: Florian Westphal <fw@strlen.de>
    Cc: Thomas Graf <tgraf@suug.ch>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    lib/nlattr.c | 10 ++++++++--
    1 file changed, 8 insertions(+), 2 deletions(-)

    diff --git a/lib/nlattr.c b/lib/nlattr.c
    index 18eca78..fc67547 100644
    --- a/lib/nlattr.c
    +++ b/lib/nlattr.c
    @@ -303,9 +303,15 @@ int nla_memcmp(const struct nlattr *nla, const void *data,
    */
    int nla_strcmp(const struct nlattr *nla, const char *str)
    {
    - int len = strlen(str) + 1;
    - int d = nla_len(nla) - len;
    + int len = strlen(str);
    + char *buf = nla_data(nla);
    + int attrlen = nla_len(nla);
    + int d;

    + if (attrlen > 0 && buf[attrlen - 1] == '\0')
    + attrlen--;
    +
    + d = attrlen - len;
    if (d == 0)
    d = memcmp(nla_data(nla), str, len);

    --
    1.9.1


    \
     
     \ /
      Last update: 2014-04-16 16:01    [W:5.751 / U:0.048 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site