netfilter buglog - Sep 2017 - [Bug 1181] New: incorrect sort function at segtree.c

https://bugzilla.netfilter.org/show_bug.cgi?id=1181

            Bug ID: 1181
           Summary: incorrect  sort function at segtree.c
           Product: nftables
           Version: unspecified
          Hardware: x86_64
                OS: All
            Status: NEW
          Severity: minor
          Priority: P5
         Component: iptables over nftable
          Assignee: pablo at netfilter.org
          Reporter: cidjey1991 at mail.ru

Created attachment 506
  --> https://bugzilla.netfilter.org/attachment.cgi?id=506&action=edit
Suggested solution

Function static int expr_value_cmp(const void *p1, const void *p2) at segtree.c
in nftables sources is incorrect.

static int expr_value_cmp(const void *p1, const void *p2)
{
    struct expr *e1 = *(void * const *)p1;
    struct expr *e2 = *(void * const *)p2;
    int ret;

    ret = mpz_cmp(expr_value(e1)->value, expr_value(e2)->value);
    if (ret == 0 && (e1->flags & EXPR_F_INTERVAL_END))
        return -1;
    else
        return 1;

    return ret;
}


as you can see, running never reaches "return ret" and basically it
doesn't
matter if mpz_cmp returned 1 or -1.

Suggested solution:

static int expr_value_cmp(const void *p1, const void *p2)
{
    struct expr *e1 = *(void * const *)p1;
    struct expr *e2 = *(void * const *)p2;
    int ret;

    ret = mpz_cmp(expr_value(e1)->value, expr_value(e2)->value);
    if (ret == 0) {
        if (e1->flags & EXPR_F_INTERVAL_END)
            return -1;
        else 
            return 1;
    } 

    return ret;
}

The patch is attached.

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https://bugzilla.netfilter.org/show_bug.cgi?id=1181

Pablo Neira Ayuso <pablo at netfilter.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #1 from Pablo Neira Ayuso <pablo at netfilter.org> ---
A very similar patch was applied few months before this report:

commit a177d08d82c4cf946324640a63581e837164dc0b
Author: Phil Sutter <phil at nwl.cc>
Date:   Thu Jul 6 16:25:28 2017 +0200

    segtree: Fix expr_value_cmp()

    Instead of returning the result of mpz_cmp(), this function returned 1
    unless both elements were equal and the first one had
    EXPR_F_INTERVAL_END set.

The update is similar to the one that this reporter suggests.

Closing.

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