MSAN + getservbyname()

[kevgs]

Hi.

#include <stdlib.h>
#include <netdb.h>

int main() {
  getservbyname("foo", NULL);
}

clang -g -fno-omit-frame-pointer -Wall -fsanitize=memory -fPIE -pie 1.c && ./a.out

Uninitialized bytes in __interceptor_strlen at offset 0 inside [0x718000000000, 49)
==1853==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x7fa2ba363cff in _nss_files_parse_servent /build/glibc-KRRWSm/glibc-2.29/nss/nss_files/files-service.c:32:1
    #1 0x7fa2ba363e6c in internal_getent /build/glibc-KRRWSm/glibc-2.29/nss/nss_files/files-XXX.c:182:22
    #2 0x7fa2ba36412e in _nss_files_getservbyname_r /build/glibc-KRRWSm/glibc-2.29/nss/nss_files/files-service.c:41:1
    #3 0x7fa2bb330f12 in getservbyname_r /build/glibc-KRRWSm/glibc-2.29/inet/../nss/getXXbyYY_r.c:315:16
    #4 0x7fa2bb330cb2 in getservbyname /build/glibc-KRRWSm/glibc-2.29/inet/../nss/getXXbyYY.c:135:7
    #5 0x56423b778467 in main /home/kevg/fun/cpp_projects/1.c:5:3
    #6 0x7fa2bb224b6a in __libc_start_main /build/glibc-KRRWSm/glibc-2.29/csu/../csu/libc-start.c:308:16
    #7 0x56423b6ff279 in _start (/home/kevg/fun/cpp_projects/a.out+0x1d279)

SUMMARY: MemorySanitizer: use-of-uninitialized-value /build/glibc-KRRWSm/glibc-2.29/nss/nss_files/files-service.c:32:1 in _nss_files_parse_servent
Exiting

I'd like to use getservbyname() with MSAN. Am I understand correct that it is missing interceptor? Or could this be a bug inside GNU libc?

[eugenis]

Yes, a missing interceptor. I don't see a source level workaround for this, unfortunately.

…

On Wed, Aug 28, 2019 at 1:50 AM Eugene Kosov ***@***.***> wrote: Hi. #include <stdlib.h> #include <netdb.h> int main() { getservbyname("foo", NULL); } clang -g -fno-omit-frame-pointer -Wall -fsanitize=memory -fPIE -pie 1.c && ./a.out Uninitialized bytes in __interceptor_strlen at offset 0 inside [0x718000000000, 49) ==1853==WARNING: MemorySanitizer: use-of-uninitialized-value #0 0x7fa2ba363cff in _nss_files_parse_servent /build/glibc-KRRWSm/glibc-2.29/nss/nss_files/files-service.c:32:1 #1 0x7fa2ba363e6c in internal_getent /build/glibc-KRRWSm/glibc-2.29/nss/nss_files/files-XXX.c:182:22 #2 0x7fa2ba36412e in _nss_files_getservbyname_r /build/glibc-KRRWSm/glibc-2.29/nss/nss_files/files-service.c:41:1 #3 0x7fa2bb330f12 in getservbyname_r /build/glibc-KRRWSm/glibc-2.29/inet/../nss/getXXbyYY_r.c:315:16 #4 0x7fa2bb330cb2 in getservbyname /build/glibc-KRRWSm/glibc-2.29/inet/../nss/getXXbyYY.c:135:7 #5 0x56423b778467 in main /home/kevg/fun/cpp_projects/1.c:5:3 #6 0x7fa2bb224b6a in __libc_start_main /build/glibc-KRRWSm/glibc-2.29/csu/../csu/libc-start.c:308:16 #7 0x56423b6ff279 in _start (/home/kevg/fun/cpp_projects/a.out+0x1d279) SUMMARY: MemorySanitizer: use-of-uninitialized-value /build/glibc-KRRWSm/glibc-2.29/nss/nss_files/files-service.c:32:1 in _nss_files_parse_servent Exiting I'd like to use getservbyname() with MSAN. Am I understand correct that it is missing interceptor? Or could this be a bug inside GNU libc? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#1138?email_source=notifications&email_token=AADG4SSLAN4LRBHMR7EGNXLQGY35HA5CNFSM4IQ7VTH2YY3PNVWWK3TUL52HS4DFUVEXG43VMWVGG33NNVSW45C7NFSM4HH3PFLQ>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AADG4SQMLR4ZJKOSHUPA5ATQGY35HANCNFSM4IQ7VTHQ> .

[kevgs]

Thanks for your answer!
You mean my source code or it's not possible to add such interceptor to compiler-rt?

[eugenis]

Your source code. Adding an interceptor would not be hard at all, but I'm swamped at the moment.

…

On Wed, Aug 28, 2019 at 12:29 PM Eugene Kosov ***@***.***> wrote: Thanks for your answer! You mean my source code or it's not possible to add such interceptor to compiler-rt? — You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

[georgthegreat]

@eugenis, could you, please give an update on the subject?