https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108541
Bug ID: 108541 Summary: ASAN since GCC 9 missed a stack-buffer-overflow Product: gcc Version: 13.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: sanitizer Assignee: unassigned at gcc dot gnu.org Reporter: shaohua.li at inf dot ethz.ch CC: dodji at gcc dot gnu.org, dvyukov at gcc dot gnu.org, jakub at gcc dot gnu.org, kcc at gcc dot gnu.org, marxin at gcc dot gnu.org Target Milestone: --- For the following code, ASAN at -O0 missed the stack-buffer-overflow while other opt levels caught it. This issue happens since GCC-9. GCC-8 and before worked fine. I also noticed that there is an incompatible pointer assignment `i = &m`, but anyway the bufferoverflow should be reported. Clang can detect it at all opt levels. Compiler explorer: https://godbolt.org/z/ovTEKG9PM % cat a.c struct a { long b; int c; long d; short e; long f; long g; }; struct { struct a b; unsigned : 6; } h, *i; int j; int main() { struct a *k; &k; long l[3]; l[j] = 4; int m = 1; i = &m; *i = h; return m; } % % gcc-tk -fsanitize=address -w -O0 a.c && ./a.out % % gcc-tk -fsanitize=address -w -O1 a.c && ./a.out ================================================================= ==1==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7f8605800030 at pc 0x0000004012e0 bp 0x7ffdfd9e9b10 sp 0x7ffdfd9e9b08 WRITE of size 56 at 0x7f8605800030 thread T0 #0 0x4012df in main /a.c:21 #1 0x7f860810f082 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24082) (BuildId: 1878e6b475720c7c51969e69ab2d276fae6d1dee) #2 0x4010cd in _start (/a.s+0x4010cd) (BuildId: 62f9205a5d8cda9f9cd98eb2592c0ba25a6a0a20) Address 0x7f8605800030 is located in stack of thread T0 at offset 48 in frame #0 0x401195 in main /app/example.c:14 This frame has 2 object(s): [48, 52) 'm' (line 19) <== Memory access at offset 48 partially overflows this variable [64, 88) 'l' (line 17) <== Memory access at offset 48 partially underflows this variable HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork (longjmp and C++ exceptions *are* supported) SUMMARY: AddressSanitizer: stack-buffer-overflow /a.c:21 in main Shadow bytes around the buggy address: ... %