git: 9efbe526e00f - main - libthr: work around an ASAN false-positive

[Alex Richardson]

The branch main has been updated by arichardson:

URL: https://cgit.FreeBSD.org/src/commit/?id=9efbe526e00f47d946b3320f595e73fea26805df

commit 9efbe526e00f47d946b3320f595e73fea26805df
Author:     Alex Richardson <arichardson at FreeBSD.org>
AuthorDate: 2021-08-02 08:49:21 +0000
Commit:     Alex Richardson <arichardson at FreeBSD.org>
CommitDate: 2021-08-02 13:33:24 +0000

    libthr: work around an ASAN false-positive
    
    I got the following error with an ASAN-instrument libthr:
    
    ==803==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7fffffffcdb0 at pc 0x000801863396 bp 0x7ff8
    READ of size 4 at 0x7fffffffcdb0 thread T0
        #0 0x801863395 in handle_signal /local/scratch/alr48/cheri/freebsd/lib/libthr/thread/thr_sig.c:262:2
        #1 0x801860da2 in thr_sighandler /local/scratch/alr48/cheri/freebsd/lib/libthr/thread/thr_sig.c:246:2
    
    Address 0x7fffffffcdb0 is located in stack of thread T0 at offset 208 in frame
        #0 0x80186080f in thr_sighandler /local/scratch/alr48/cheri/freebsd/lib/libthr/thread/thr_sig.c:213
    
      This frame has 1 object(s):
        [32, 64) 'act' (line 216) <== Memory access at offset 208 overflows this variable
    HINT: this may be a false positive if your program uses some custom stack
    
    This seems like a false-positive since the line in question is
    `SIGSETOR(actp->sa_mask, ucp->uc_sigmask);` and it complains about a read
    operation (from the ucontext_t argument) so this indicates to me that ASAN
    does not understand that thr_sighandler() is a signal handler.
    
    Differential Revision: https://reviews.freebsd.org/D31074
---
 lib/libthr/Makefile | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/libthr/Makefile b/lib/libthr/Makefile
index 1a5dfa18dca7..038823413cb2 100644
--- a/lib/libthr/Makefile
+++ b/lib/libthr/Makefile
@@ -29,6 +29,12 @@ CFLAGS+=-I${SRCTOP}/lib/libthread_db
 CFLAGS.thr_stack.c+=	-Wno-cast-align
 CFLAGS.rtld_malloc.c+=	-Wno-cast-align
 CFLAGS.thr_symbols.c+=	-Wno-missing-variable-declarations
+.if ${MK_ASAN} != "no"
+# False-positive ASAN error claiming the local "struct sigaction act;" is
+# overflowed by handle_signal() reading from the ucontext_t argument. This
+# could be caused by ASAN not treating this function as a signal handler.
+CFLAGS.thr_sig.c+=	-fno-sanitize=address
+.endif
 
 .ifndef NO_THREAD_UNWIND_STACK
 CFLAGS+=-fexceptions