Port, board and/or hardware

unix port, coverage, x86_64

MicroPython version

MicroPython v1.26.0-preview.521.g658a2e3dbd on 2025-08-02; linux [GCC 12.2.0] version

Reproduction

Run micropython with a snippet of unusual code:

$ ./build-coverage/micropython -c 'ans = (-1) ** 2.3; aa'
Segmentation fault

Expected behaviour

A NameError, because aa is not defined

Observed behaviour

A segfault

Additional Information

The stack trace is corrupt. ubsan asan all failed to give more useful info.

Program received signal SIGSEGV, Segmentation fault.
0x0000555555756530 in mp_state_ctx ()
(gdb) where
#0  0x0000555555756530 in mp_state_ctx ()
#1  0x0000000000000000 in ?? ()

valgrind produced multiple diagnostics beginning with this, which looks interesting:

==1669951== Invalid write of size 8
==1669951==    at 0x16C3B4: nlr_jump (nlrx64.c:104)
==1669951==    by 0x1B23DE: fun_bc_call (objfun.c:352)
==1669951==    by 0x19E61E: mp_call_function_n_kw (runtime.c:727)
==1669951==    by 0x1A0DEA: mp_call_function_0 (runtime.c:701)
==1669951==    by 0x264DB8: execute_from_lexer (main.c:162)
==1669951==    by 0x264E67: do_str (main.c:315)
==1669951==    by 0x2658D3: main_ (main.c:656)
==1669951==    by 0x26619F: main (main.c:494)
==1669951==  Address 0x1ffefff888 is on thread 1's stack
==1669951==  232 bytes below stack pointer

I think there's something going on where an nlr jmp_buf registered inside fold_constants is somehow coming into play later when the NameError is thrown:

Breakpoint 1, nlr_push (nlr=nlr@entry=0x7fffffffdb10) at ../../py/nlrx64.c:55
55	unsigned int nlr_push(nlr_buf_t *nlr) {
(gdb) where
#0  nlr_push (nlr=nlr@entry=0x7fffffffdb10) at ../../py/nlrx64.c:55
#1  0x00005555556b0ae5 in execute_from_lexer (source_kind=source_kind@entry=1, 
    source=0x7fffffffe1a9, input_kind=input_kind@entry=MP_PARSE_FILE_INPUT, 
    is_repl=is_repl@entry=false) at main.c:123
#2  0x00005555556b0e68 in do_str (str=<optimized out>) at main.c:315
#3  0x00005555556b18d4 in main_ (argc=argc@entry=3, argv=argv@entry=0x7fffffffddd8)
    at main.c:656
#4  0x00005555556b21a0 in main (argc=3, argv=0x7fffffffddd8) at main.c:494
(gdb) c
Continuing.

Breakpoint 1, nlr_push (nlr=nlr@entry=0x7fffffffd900) at ../../py/nlrx64.c:55
55	unsigned int nlr_push(nlr_buf_t *nlr) {
(gdb) where
#0  nlr_push (nlr=nlr@entry=0x7fffffffd900) at ../../py/nlrx64.c:55
#1  0x00005555555c5ea3 in binary_op_maybe (op=op@entry=MP_BINARY_OP_POWER, 
    lhs=0xffffffffffffffff, rhs=0x7ffff7c491e0, res=res@entry=0x7fffffffd998)
    at ../../py/parse.c:672
#2  0x00005555555c6d42 in fold_constants (parser=parser@entry=0x7fffffffda30, 
    rule_id=rule_id@entry=42 '*', num_args=2) at ../../py/parse.c:780
#3  0x00005555555c6ac2 in push_result_rule (parser=parser@entry=0x7fffffffda30, src_line=1, 
    rule_id=rule_id@entry=42 '*', num_args=<optimized out>) at ../../py/parse.c:1033
#4  0x00005555555c86b7 in mp_parse (lex=lex@entry=0x7ffff7c48bc0, 
    input_kind=input_kind@entry=MP_PARSE_FILE_INPUT) at ../../py/parse.c:1263
#5  0x00005555556b0b5c in execute_from_lexer (source_kind=source_kind@entry=1, 
    source=<optimized out>, input_kind=input_kind@entry=MP_PARSE_FILE_INPUT, 
    is_repl=is_repl@entry=false) at main.c:147
#6  0x00005555556b0e68 in do_str (str=<optimized out>) at main.c:315
#7  0x00005555556b18d4 in main_ (argc=argc@entry=3, argv=argv@entry=0x7fffffffddd8)
    at main.c:656
#8  0x00005555556b21a0 in main (argc=3, argv=0x7fffffffddd8) at main.c:494
(gdb) c
Continuing.

Breakpoint 1, nlr_push (nlr=nlr@entry=0x7fffffffd990) at ../../py/nlrx64.c:55
55	unsigned int nlr_push(nlr_buf_t *nlr) {
(gdb) where
#0  nlr_push (nlr=nlr@entry=0x7fffffffd990) at ../../py/nlrx64.c:55
#1  0x00005555556218fa in mp_execute_bytecode (code_state=code_state@entry=0x7fffffffda20, 
    inject_exc=<optimized out>, inject_exc@entry=0x0) at ../../py/vm.c:301
#2  0x00005555555fe288 in fun_bc_call (self_in=0x7ffff7c48be0, n_args=0, n_kw=0, args=0x0)
    at ../../py/objfun.c:295
#3  0x00005555555ea61f in mp_call_function_n_kw (fun_in=0x7ffff7c48be0, 
    n_args=n_args@entry=0, n_kw=n_kw@entry=0, args=args@entry=0x0) at ../../py/runtime.c:727
#4  0x00005555555ecdeb in mp_call_function_0 (fun=<optimized out>) at ../../py/runtime.c:701
#5  0x00005555556b0db9 in execute_from_lexer (source_kind=source_kind@entry=1, 
    source=<optimized out>, input_kind=input_kind@entry=MP_PARSE_FILE_INPUT, 
    is_repl=is_repl@entry=false) at main.c:162
#6  0x00005555556b0e68 in do_str (str=<optimized out>) at main.c:315
#7  0x00005555556b18d4 in main_ (argc=argc@entry=3, argv=argv@entry=0x7fffffffddd8)
    at main.c:656
#8  0x00005555556b21a0 in main (argc=3, argv=0x7fffffffddd8) at main.c:494
(gdb) c
Continuing.

Breakpoint 2, nlr_jump (val=0x7ffff7c48ba0) at ../../py/nlrx64.c:103
103	MP_NORETURN void nlr_jump(void *val) {
(gdb) p mp_thread_get_state ()->nlr_top
$3 = (nlr_buf_t *) 0x7fffffffd990
(gdb) c
Continuing.

Breakpoint 2, nlr_jump (val=val@entry=0x7ffff7c48ba0) at ../../py/nlrx64.c:103
103	MP_NORETURN void nlr_jump(void *val) {
(gdb) p mp_thread_get_state ()->nlr_top
$4 = (nlr_buf_t *) 0x7fffffffd900
(gdb) where
#0  nlr_jump (val=val@entry=0x7ffff7c48ba0) at ../../py/nlrx64.c:103
#1  0x00005555555fe3df in fun_bc_call (self_in=<optimized out>, n_args=0, n_kw=0, args=0x0)
    at ../../py/objfun.c:352
#2  0x00005555555ea61f in mp_call_function_n_kw (fun_in=0x7ffff7c48be0, 
    n_args=n_args@entry=0, n_kw=n_kw@entry=0, args=args@entry=0x0) at ../../py/runtime.c:727
#3  0x00005555555ecdeb in mp_call_function_0 (fun=<optimized out>) at ../../py/runtime.c:701
#4  0x00005555556b0db9 in execute_from_lexer (source_kind=source_kind@entry=1, 
    source=<optimized out>, input_kind=input_kind@entry=MP_PARSE_FILE_INPUT, 
    is_repl=is_repl@entry=false) at main.c:162
#5  0x00005555556b0e68 in do_str (str=<optimized out>) at main.c:315
#6  0x00005555556b18d4 in main_ (argc=argc@entry=3, argv=argv@entry=0x7fffffffddd8)
    at main.c:656
#7  0x00005555556b21a0 in main (argc=3, argv=0x7fffffffddd8) at main.c:494

notice how the last nlr_buf_t in nlr_jmp is equal to the one inside the stack including binary_op_maybe called from fold_constants even though those are no longer on the stack.

This crash was found with AFLplusplus and minimized manually.

Code of Conduct

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