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msan: check that ucontext_t is initialized on signal return 

A signal handler can alter ucontext_t to affect execution after
the signal returns. Check that the contents are initialized.
Restoring unitialized values in registers can't be good.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D116209
This commit is contained in:
Dmitry Vyukov 2021-12-23 09:10:54 +01:00
parent 1298273e82
commit 395f737c33
2 changed files with 28 additions and 0 deletions
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1
compiler-rt/lib/msan/msan_interceptors.cpp
View File

@ -996,6 +996,7 @@ static void SignalAction(int signo, void *si, void *uc) {
sigaction_cb cb =
(sigaction_cb)atomic_load(&sigactions[signo], memory_order_relaxed);
cb(signo, si, uc);
CHECK_UNPOISONED(uc, ucontext_t_sz(uc));
}
static void read_sigaction(const __sanitizer_sigaction *act) {

27
compiler-rt/test/msan/Linux/signal_mcontext2.cpp Normal file
View File

@ -0,0 +1,27 @@
// RUN: %clangxx_msan -fsanitize-memory-track-origins=2 -O1 %s -o %t && not %run %t 2>&1 | FileCheck %s
#include <pthread.h>
#include <signal.h>
#include <ucontext.h>
void handler(int sig, siginfo_t *info, void *uctx) {
volatile int uninit;
auto *mctx = &static_cast<ucontext_t *>(uctx)->uc_mcontext;
auto *fpregs = mctx->fpregs;
if (fpregs && fpregs->__glibc_reserved1[12] == FP_XSTATE_MAGIC1)
reinterpret_cast<_xstate *>(mctx->fpregs)->ymmh.ymmh_space[0] = uninit;
else
mctx->gregs[REG_RAX] = uninit;
}
int main(int argc, char **argv) {
struct sigaction act = {};
act.sa_sigaction = handler;
act.sa_flags = SA_SIGINFO;
sigfillset(&act.sa_mask);
sigaction(SIGPROF, &act, 0);
pthread_kill(pthread_self(), SIGPROF);
return 0;
}
// CHECK: WARNING: MemorySanitizer: