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Fix sigaction interceptor to always correctly populate oldact 

This fixes https://bugs.llvm.org/show_bug.cgi?id=47118. Before this change, when the sigaction interceptor prevented a signal from being changed, it also prevented the oldact output parameter from being written to. This resulted in a use-of-uninitialized-variable by any program that used sigaction for the purpose of reading signals.

This change fixes this: the regular sigaction implementation is still called, but with the act parameter nullified, preventing any changes.

Patch By: IanPudney

Reviewed By: morehouse

Differential Revision: https://reviews.llvm.org/D85797
This commit is contained in:
Matt Morehouse 2020-08-12 09:19:25 -07:00
parent ce2c991061
commit fd893bda55
2 changed files with 29 additions and 1 deletions
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5
compiler-rt/lib/sanitizer_common/sanitizer_signal_interceptors.inc
View File

@ -53,7 +53,10 @@ INTERCEPTOR(uptr, signal, int signum, uptr handler) {
INTERCEPTOR(int, sigaction_symname, int signum,
const __sanitizer_sigaction *act, __sanitizer_sigaction *oldact) {
if (GetHandleSignalMode(signum) == kHandleSignalExclusive) return 0;
if (GetHandleSignalMode(signum) == kHandleSignalExclusive) {
if (!oldact) return 0;
act = nullptr;
}
SIGNAL_INTERCEPTOR_SIGACTION_IMPL(signum, act, oldact);
}
#define INIT_SIGACTION COMMON_INTERCEPT_FUNCTION(sigaction_symname)

25
compiler-rt/test/msan/interception_sigaction_test.cpp Normal file
View File

@ -0,0 +1,25 @@
// RUN: %clangxx_msan -O0 -g %s -o %t
// RUN: MSAN_OPTIONS=handle_segv=2 %t 2>&1 | FileCheck %s
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <string.h>
extern "C" int __interceptor_sigaction(int signum, const struct sigaction *act, struct sigaction *oldact);
extern "C" int sigaction(int signum, const struct sigaction *act, struct sigaction *oldact) {
write(2, "sigaction call\n", sizeof("sigaction call\n") - 1);
return __interceptor_sigaction(signum, act, oldact);
}
int main() {
struct sigaction oldact;
sigaction(SIGSEGV, nullptr, &oldact);
if (oldact.sa_handler || oldact.sa_sigaction) {
fprintf(stderr, "oldact filled\n");
}
return 0;
// CHECK: sigaction call
// CHECK: oldact filled
}