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Bypass potential libc's sysconf wrappers for sysconf(_SC_PAGESIZE) call 

Summary:
sysconf(_SC_PAGESIZE) is called very early, during sanitizer init and
any instrumented code (a wrapper/interceptor will likely be instrumented)
calling back to sanitizer before init is done will most surely crash.

Reviewers: eugenis

Subscribers: llvm-commits, kubamracek

Differential Revision: https://reviews.llvm.org/D31092

llvm-svn: 298305
This commit is contained in:
Alex Shlyapnikov 2017-03-20 21:03:28 +00:00
parent 5378e423e5
commit a7291b3730
2 changed files with 24 additions and 0 deletions
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3
compiler-rt/lib/sanitizer_common/sanitizer_linux.cc
View File

@ -78,6 +78,7 @@ extern char **environ; // provided by crt1
#endif
#if SANITIZER_LINUX
#include <sys/auxv.h>
// <linux/time.h>
struct kernel_timeval {
long tv_sec;
@ -805,6 +806,8 @@ uptr GetPageSize() {
return 4096;
#elif SANITIZER_LINUX && (defined(__x86_64__) || defined(__i386__))
return EXEC_PAGESIZE;
#elif SANITIZER_LINUX
return getauxval(AT_PAGESZ);
#else
return sysconf(_SC_PAGESIZE); // EXEC_PAGESIZE may not be trustworthy.
#endif

21
compiler-rt/test/sanitizer_common/TestCases/Linux/sysconf_interceptor_bypass_test.cc Normal file
View File

@ -0,0 +1,21 @@
// RUN: %clangxx -O2 %s -o %t && %run %t 2>&1 | FileCheck %s
#include <stdio.h>
extern "C" long sysconf(int name) {
fprintf(stderr, "sysconf wrapper called\n");
return 0;
}
int main() {
// All we need to check is that the sysconf() interceptor defined above was
// not called. Should it get called, it will crash right there, any
// instrumented code executed before sanitizer init is finished will crash
// accessing non-initialized sanitizer internals. Even if it will not crash
// in some configuration, it should never be called anyway.
fprintf(stderr, "Passed\n");
// CHECK-NOT: sysconf wrapper called
// CHECK: Passed
// CHECK-NOT: sysconf wrapper called
return 0;
}