This is the mail archive of the glibc-bugs@sourceware.org mailing list for the glibc project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[Bug nss/19741] New: m68k: Assertion failure in gethostbyname


https://sourceware.org/bugzilla/show_bug.cgi?id=19741

            Bug ID: 19741
           Summary: m68k: Assertion failure in gethostbyname
           Product: glibc
           Version: 2.21
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nss
          Assignee: unassigned at sourceware dot org
          Reporter: jrtc27 at jrtc27 dot com
  Target Milestone: ---

It seems gethostbyname is broken, failing for me with
ânss_files/files-hosts.c:218: _nss_files_gethostbyname3_r: Assertion
`(bufferend - (char *) 0) % sizeof (char *) == 0' failed.â This can be
reproduced with the following simple program:

    #include <stdio.h>
    #include <netdb.h>

    int main(int argc, char **argv) {
        struct hostent *h = gethostbyname("localhost");
        printf("name: %s\n", h->h_name);
        return 0;
    }

Delving inside glibc, _nss_files_gethostbyname3_r expects result->h_aliases to
be aligned to sizeof(char *), as can be seen in the assert (bufferend points to
an element in result->h_aliases, and each element is a char *). Provided this
is true when the function is called, it seems to correctly maintain the
invariant by rounding up bufferend when necessary.

However, the initial value of result->h_aliases is not aligned to sizeof(char
*). Instead, it is assigned in parse_list (nss_files/files-parse.c:245) and
aligned to __alignof__(char *). On many architectures, these are the same, but
on m68k, __alignof__(char *) == 2, but sizeof(char *) == 4. There may be
environments where result->h_aliases happens to be aligned to sizeof(char *) by
chance, but that is most certainly not the case on mine (latest unstable
running in ARAnyM).

I donât know why bufferend is required to be aligned to sizeof(char *), and
believe that imposing __alignof__(char *) in _nss_files_gethostbyname3_r
instead would suffice. Alternatively, parse_list could choose MAX(sizeof(char
*), __alignof__(char *)) as the alignment. Either way, the implementation as a
whole is currently broken.

-- 
You are receiving this mail because:
You are on the CC list for the bug.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]