[Bug network/14806] New: stack overflow in getaddrinfo() when host has many addresses

[mkubecek at suse dot cz]

http://sourceware.org/bugzilla/show_bug.cgi?id=14806

             Bug #: 14806
           Summary: stack overflow in getaddrinfo() when host has many
                    addresses
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: network
        AssignedTo: unassigned@sourceware.org
        ReportedBy: mkubecek@suse.cz
    Classification: Unclassified


Created attachment 6720
  --> http://sourceware.org/bugzilla/attachment.cgi?id=6720
proposed fix

Function make_request() in sysdeps/unix/sysv/linux/check_pf.c uses alloca() to
allocate memory for the temporary linked list of local addresses. If the host
has many addresses (originally observed with more than 7000 addresses and 256
KB stack size limit), this can cause stack overflow.

Attached is a fix proposal which is a bit more complicated than necessary but I
wanted to avoid

  (1) calling malloc() in the most common case when there are just a few
      addresses
  (2) allocating many small blocks if there are many addresses
  (3) allocating too much memory on stack

Thus the patch allocates a small block for 16 addresses on stack; if this is
not enough (usually it is), linked list of blocks for 64 addresses is allocated
as needed (suitable values of 16 and 64 are open to discussion).

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