[DFSan] Add pthread and other functions to ABI list.

[morehouse]

Summary

The non-pthread functions are all clear discard functions.

Some of the pthread ones could clear shadow, but aren't worth writing
custom wrappers for. I can't think of any reasonable scenario where we
would pass tainted memory to these pthread functions.

[stephan.yichao.zhao]

compiler-rt/lib/dfsan/done_abilist.txt

99

https://screenshot.googleplex.com/7FRxwMRnWiJPqWg says the output pointed by the pointer could be depending on its input content? but I am not sure since I've never used it.
Would a custom wrapper be better?

116

create?

261

If it returns pthread_attr_setaffinity_np's input, the flow is discarded.
Maybe both these setter and getters are custom.

[morehouse]

compiler-rt/lib/dfsan/done_abilist.txt

99

The source code in glibc is https://code.woboq.org/userspace/glibc/sysdeps/unix/sysv/linux/cmsg_nxthdr.c.html.

It returns a pointer at some offset from the input parameter cmsg, without writing any data. Since no data is written, I figure discard is sufficient.

If we want to get really strict, we can use a custom wrapper to combine labels for every single field accessed from mhdr and cmsg, but maybe it's overkill.

116

Not a typo: https://man7.org/linux/man-pages/man2/creat.2.html

261

This is true. The question is whether it's worth tracking that flow or not.

My argument for why it's not worth it:

• It seems rare that we would need to track flow through pthread_attr_ts.
• The definition of pthread_attr_t is an implementation detail of the pthread library not exposed in the public API. So it could easily change in different versions. Any custom wrapper would require maintenance burden to be kept up-to-date with the latest pthread library.

[stephan.yichao.zhao]

compiler-rt/lib/dfsan/done_abilist.txt

261

Thank you for the explanation.

Does DFSan pass have an opportunity to visit the functions during compilation?
It can create the summary automatically by analyzing its code.
But I guess it does not...

[morehouse]

compiler-rt/lib/dfsan/done_abilist.txt

261

I wish it did. Both glibc and pthreads are precompiled on the system, which means we have to use the ABI list for all their functions. Even if we could compile glibc with DFSan, it has a lot of assembly code we would still need to use the ABI list for.

llvm-libc may help when it is more complete.

compiler-rt/lib/dfsan/done_abilist.txt

 fun:sqrt=functional
 fun:sqrtf=functional
 fun:sqrtl=functional
 fun:wctob=functional
 
 # Functions that produce an output that does not depend on the input (shadow is
 # zeroed automatically).
 fun:__assert_fail=discard
+fun:__cmsg_nxthdr=discard
 fun:__ctype_b_loc=discard
 fun:__cxa_atexit=discard
 fun:__errno_location=discard
 fun:__newlocale=discard
 fun:__sbrk=discard
 fun:__sigsetjmp=discard
 fun:__uselocale=discard
 fun:__wctype_l=discard
 fun:access=discard
 fun:alarm=discard
 fun:atexit=discard
 fun:bind=discard
 fun:chdir=discard
 fun:close=discard
 fun:closedir=discard
 fun:connect=discard
+fun:creat=discard
 fun:dladdr=discard
 fun:dlclose=discard
+fun:epoll_ctl=discard
 fun:fclose=discard
 fun:feof=discard
 fun:ferror=discard
 fun:fflush=discard
 fun:fileno=discard
 fun:fopen=discard
 fun:fprintf=discard
 fun:fputc=discard

 fun:getpid=discard
 fun:kill=discard
 fun:listen=discard
 fun:lseek=discard
 fun:mkdir=discard
 fun:mmap=discard
 fun:munmap=discard
 fun:open=discard
+fun:openat=discard
 fun:pipe=discard
 fun:posix_fadvise=discard
 fun:posix_memalign=discard
 fun:prctl=discard
 fun:printf=discard
 fun:pthread_sigmask=discard
 fun:putc=discard
 fun:putchar=discard

 
 # TODO: custom
 fun:asprintf=discard
 fun:qsort=discard
 
 ###############################################################################
 # pthread
 ###############################################################################
+fun:__pthread_register_cancel=discard
+fun:__pthread_unregister_cancel=discard
+fun:pthread_attr_destroy=discard
+fun:pthread_attr_getaffinity_np=discard
+fun:pthread_attr_getdetachstate=discard
+fun:pthread_attr_getguardsize=discard
+fun:pthread_attr_getinheritsched=discard
+fun:pthread_attr_getschedparam=discard
+fun:pthread_attr_getschedpolicy=discard
+fun:pthread_attr_getscope=discard
+fun:pthread_attr_getstack=discard
+fun:pthread_attr_getstackaddr=disacrd
+fun:pthread_attr_getstacksize=discard
+fun:pthread_attr_init=discard
+fun:pthread_attr_setaffinity_np=discard
+fun:pthread_attr_setdetachstate=discard
+fun:pthread_attr_setguardsize=discard
+fun:pthread_attr_setinheritsched=discard
+fun:pthread_attr_setschedparam=discard
+fun:pthread_attr_setschedpolicy=discard
+fun:pthread_attr_setscope=discard
+fun:pthread_attr_setstack=discard
+fun:pthread_attr_setstackaddr=discard
+fun:pthread_attr_setstacksize=discard
 fun:pthread_equal=discard
+fun:pthread_getschedparam=discard
 fun:pthread_getspecific=discard
 fun:pthread_key_create=discard
 fun:pthread_key_delete=discard
 fun:pthread_mutex_destroy=discard
 fun:pthread_mutex_init=discard
 fun:pthread_mutex_lock=discard
 fun:pthread_mutex_trylock=discard
 fun:pthread_mutex_unlock=discard
 fun:pthread_mutexattr_destroy=discard
 fun:pthread_mutexattr_init=discard
 fun:pthread_mutexattr_settype=discard
+fun:pthread_rwlock_destroy=discard
+fun:pthread_rwlock_init=discard
+fun:pthread_rwlock_rdlock=discard
+fun:pthread_rwlock_timedrdlock=discard
+fun:pthread_rwlock_timedwrlock=discard
+fun:pthread_rwlock_tryrdlock=discard
+fun:pthread_rwlock_trywrlock=discard
+fun:pthread_rwlock_wrlock=discard
+fun:pthread_rwlock_unlock=discard
+fun:pthread_setschedparam=discard
+fun:pthread_setname_np=discard
 fun:pthread_once=discard
 fun:pthread_self=discard
 fun:pthread_setspecific=discard
 
 # Functions that take a callback (wrap the callback manually).
 fun:pthread_create=custom
 
 ###############################################################################