[RFC,v2,05/36] libsepol/fuzz: limit element sizes for fuzzing

Commit Message

Christian Göttsche Nov. 5, 2021, 3:45 p.m. UTC

Limit the maximum length of read sizes, like string length of module
version and name or keys and number of symtab entries.  This avoids the
fuzzer to report oom events for huge allocations (it also improves the
number of executions per seconds of the fuzzer).

This change only affects the fuzzer build.

    ==15211== ERROR: libFuzzer: out-of-memory (malloc(3115956666))
       To change the out-of-memory limit use -rss_limit_mb=<N>

        #0 0x52dc61 in __sanitizer_print_stack_trace (./out/binpolicy-fuzzer+0x52dc61)
        #1 0x475618 in fuzzer::PrintStackTrace() fuzzer.o
        #2 0x458855 in fuzzer::Fuzzer::HandleMalloc(unsigned long) fuzzer.o
        #3 0x45876a in fuzzer::MallocHook(void const volatile*, unsigned long) fuzzer.o
        #4 0x534557 in __sanitizer::RunMallocHooks(void const*, unsigned long) (./out/binpolicy-fuzzer+0x534557)
        #5 0x4aa7d7 in __asan::Allocator::Allocate(unsigned long, unsigned long, __sanitizer::BufferedStackTrace*, __asan::AllocType, bool) (./out/binpolicy-fuzzer+0x4aa7d7)
        #6 0x4aa143 in __asan::asan_malloc(unsigned long, __sanitizer::BufferedStackTrace*) (./out/binpolicy-fuzzer+0x4aa143)
        #7 0x5259cb in malloc (./out/binpolicy-fuzzer+0x5259cb)
        #8 0x59d307 in str_read ./libsepol/src/services.c:1746:8
        #9 0x585b97 in perm_read ./libsepol/src/policydb.c:2063:5
        #10 0x581f8a in common_read ./libsepol/src/policydb.c:2119:7
        #11 0x576681 in policydb_read ./libsepol/src/policydb.c:4417:8
        #12 0x55a214 in LLVMFuzzerTestOneInput ./libsepol/fuzz/binpolicy-fuzzer.c:26:6
        #13 0x45aed3 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) fuzzer.o
        #14 0x446a12 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) fuzzer.o
        #15 0x44c93b in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) fuzzer.o
        #16 0x475dd2 in main (./out/binpolicy-fuzzer+0x475dd2)
        #17 0x7fe1ec88a7ec in __libc_start_main csu/../csu/libc-start.c:332:16
        #18 0x423689 in _start (./out/binpolicy-fuzzer+0x423689)

    ==12683== ERROR: libFuzzer: out-of-memory (malloc(2526451450))
       To change the out-of-memory limit use -rss_limit_mb=<N>

        #0 0x52dc61 in __sanitizer_print_stack_trace (./out/binpolicy-fuzzer+0x52dc61)
        #1 0x475618 in fuzzer::PrintStackTrace() fuzzer.o
        #2 0x458855 in fuzzer::Fuzzer::HandleMalloc(unsigned long) fuzzer.o
        #3 0x45876a in fuzzer::MallocHook(void const volatile*, unsigned long) fuzzer.o
        #4 0x534557 in __sanitizer::RunMallocHooks(void const*, unsigned long) (./out/binpolicy-fuzzer+0x534557)
        #5 0x4aa7d7 in __asan::Allocator::Allocate(unsigned long, unsigned long, __sanitizer::BufferedStackTrace*, __asan::AllocType, bool) (./out/binpolicy-fuzzer+0x4aa7d7)
        #6 0x4aa143 in __asan::asan_malloc(unsigned long, __sanitizer::BufferedStackTrace*) (./out/binpolicy-fuzzer+0x4aa143)
        #7 0x5259cb in malloc (./out/binpolicy-fuzzer+0x5259cb)
        #8 0x575f8a in policydb_read ./libsepol/src/policydb.c:4356:18
        #9 0x55a214 in LLVMFuzzerTestOneInput ./libsepol/fuzz/binpolicy-fuzzer.c:26:6
        #10 0x45aed3 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) fuzzer.o
        #11 0x446a12 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) fuzzer.o
        #12 0x44c93b in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) fuzzer.o
        #13 0x475dd2 in main (./out/binpolicy-fuzzer+0x475dd2)
        #14 0x7fa737b377ec in __libc_start_main csu/../csu/libc-start.c:332:16
        #15 0x423689 in _start (./out/binpolicy-fuzzer+0x423689)

Signed-off-by: Christian Göttsche <[e-mail]>
---
 libsepol/src/private.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Patch

diff --git a/libsepol/src/private.h b/libsepol/src/private.h
index 71287282..6146f59f 100644
--- a/libsepol/src/private.h
+++ b/libsepol/src/private.h
@@ -44,7 +44,12 @@ 
 
 #define ARRAY_SIZE(x) (sizeof(x)/sizeof((x)[0]))
 
-#define is_saturated(x) (x == (typeof(x))-1)
+#ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
+# define is_saturated(x) (x == (typeof(x))-1 || (x) > (1U << 16))
+#else
+# define is_saturated(x) (x == (typeof(x))-1)
+#endif
+
 #define zero_or_saturated(x) ((x == 0) || is_saturated(x))
 
 #define spaceship_cmp(a, b) (((a) > (b)) - ((a) < (b)))