gh-130052: Fix search_map_for_section() error handling by vstinner · Pull Request #132594 · python/cpython · GitHub

Don't call close() if the file descriptor is negative.
If close() fails, chain the existing exception.

Issue: Some error paths do not set Exceptions in _testexternalinspection #130052

* Don't call close() if the file descriptor is negative. * If close() fails, chain the existing exception.

Example to trigger #130052 (comment) bug.

Apply the patch:

diff --git a/Modules/_testexternalinspection.c b/Modules/_testexternalinspection.c
index e90cfb9132b..dfb874c2f9a 100644
--- a/Modules/_testexternalinspection.c
+++ b/Modules/_testexternalinspection.c
@@ -335,6 +335,7 @@ search_map_for_section(pid_t pid, const char* secname, const char* map)
     uintptr_t result = 0;
     void* file_memory = NULL;
 
+elf_file[0] = 'X';
     int fd = open(elf_file, O_RDONLY);
     if (fd < 0) {
         PyErr_SetFromErrno(PyExc_OSError);

Run the test:

$ ./python -m test -v test_external_inspection -v
(...)
0:00:00 load avg: 0.91 [1/1] test_external_inspection
test_async_gather_remote_stack_trace (test.test_external_inspection.TestGetStackTrace.test_async_gather_remote_stack_trace) ...

python: Objects/call.c:342: _PyObject_Call: Assertion `!_PyErr_Occurred(tstate)' failed.
Fatal Python error: Aborted

Current thread 0x00007fc09e64d780 [python] (most recent call first):
  File "/home/vstinner/python/main/Lib/test/test_external_inspection.py", line 271 in test_async_gather_remote_stack_trace
  (...)

Extension modules: _testinternalcapi, _testexternalinspection (total: 2)
Abandon (core dumped)

LGTM thanks a lot @vstinner

There is another bug in find_map_start_address(), it fails to retrieve the ELF filename in some cases. But I chose to focus on the first most urgent bug. The bug is hard is reproduce.

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

…H-132594) * Don't call close() if the file descriptor is negative. * If close() fails, chain the existing exception. (cherry picked from commit 014c7f9) Co-authored-by: Victor Stinner <vstinner@python.org>

GH-132598 is a backport of this pull request to the 3.13 branch.

) (#132598) gh-130052: Fix search_map_for_section() error handling (GH-132594) * Don't call close() if the file descriptor is negative. * If close() fails, chain the existing exception. (cherry picked from commit 014c7f9) Co-authored-by: Victor Stinner <vstinner@python.org>

@vstinner thanks for the fix! Do you want me to look at the second bug?

Do you want me to look at the second bug?

If you want. Sometimes, find_map_start_address() fails to parse the ELF filename and so open() fails. For example, the filename starts with spaces and ends with a newline. I don't know how to reproduce the bug in a reliable way.

If you want. Sometimes, find_map_start_address() fails to parse the ELF filename and so open() fails. For example, the filename starts with spaces and ends with a newline. I don't know how to reproduce the bug in a reliable way.

It seems that @pablogsal fixed this, at least he handle \n in the latest code:

cpython/Python/remote_debug.h

Lines 524 to 539 in 56c88e4

    
           while (fgets(line + linelen, linesz - linelen, maps_file) != NULL) { 
        
               linelen = strlen(line); 
        
               if (line[linelen - 1] != '\n') { 
        
                   // Read a partial line: realloc and keep reading where we left off. 
        
                   // Note that even the last line will be terminated by a newline. 
        
                   linesz *= 2; 
        
                   char *biggerline = PyMem_Realloc(line, linesz); 
        
                   if (!biggerline) { 
        
                       PyMem_Free(line); 
        
                       fclose(maps_file); 
        
                       PyErr_NoMemory(); 
        
                       return 0; 
        
                   } 
        
                   line = biggerline; 
        
                   continue; 
        
               }

.

I tried to reproduce, but python doesn't run at all.

root@s512:~/sources/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111/2222222222222222222-2222222222222222222-2222222222222222222-2222222222222222222-2222222222222222222/33333333333333333333333333333-33333333333333333333333333333-33333333333333333333333333333/cpython# ./python -m test -v test_external_inspection 
Exception ignored while running getpath:
Traceback (most recent call last):
  File "<frozen getpath>", line 361, in <module>
SystemError: failed to join paths
Fatal Python error: error evaluating path
Python runtime state: core initialized

Stack (most recent call first):
  <no Python frame>

pythongh-130052 : Fix search_map_for_section() error handling

8c71d19

* Don't call close() if the file descriptor is negative. * If close() fails, chain the existing exception.

vstinner added skip news needs backport to 3.13 bugs and security fixes labels Apr 16, 2025

bedevere-app Bot added awaiting core review tests Tests in the Lib/test dir labels Apr 16, 2025

bedevere-app Bot mentioned this pull request Apr 16, 2025

Some error paths do not set Exceptions in _testexternalinspection #130052

Closed

pablogsal approved these changes Apr 16, 2025

View reviewed changes

bedevere-app Bot added awaiting merge and removed awaiting core review labels Apr 16, 2025

vstinner enabled auto-merge (squash) April 16, 2025 13:55

vstinner merged commit 014c7f9 into python:main Apr 16, 2025

vstinner deleted the search_map branch April 16, 2025 13:56

bedevere-app Bot removed the awaiting merge label Apr 16, 2025

bedevere-app Bot removed the needs backport to 3.13 bugs and security fixes label Apr 16, 2025

gh-130052: Fix search_map_for_section() error handling by vstinner · Pull Request #132594 · python/cpython · GitHub

Uh oh!

Uh oh!

gh-130052: Fix search_map_for_section() error handling - #132594

gh-130052: Fix search_map_for_section() error handling#132594
vstinner merged 1 commit into
python:mainfrom
vstinner:search_map

vstinner commented Apr 16, 2025 •
edited by bedevere-app Bot
Loading

Uh oh!

Uh oh!

vstinner commented Apr 16, 2025

Uh oh!

vstinner commented Apr 16, 2025

Uh oh!

pablogsal commented Apr 16, 2025

Uh oh!

vstinner commented Apr 16, 2025

Uh oh!

miss-islington-app Bot commented Apr 16, 2025

Uh oh!

bedevere-app Bot commented Apr 16, 2025

Uh oh!

sergey-miryanov commented Apr 16, 2025

Uh oh!

vstinner commented Apr 17, 2025

Uh oh!

sergey-miryanov commented Apr 26, 2025

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

gh-130052: Fix search_map_for_section() error handling by vstinner · Pull Request #132594 · python/cpython · GitHub

Uh oh!

Uh oh!

gh-130052: Fix search_map_for_section() error handling - #132594

gh-130052: Fix search_map_for_section() error handling#132594vstinner merged 1 commit intopython:mainpython/cpython:mainfrom vstinner:search_mapvstinner/cpython:search_mapCopy head branch name to clipboard

Conversation

vstinner commented Apr 16, 2025 • edited by bedevere-app Bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

vstinner commented Apr 16, 2025

Uh oh!

vstinner commented Apr 16, 2025

Uh oh!

pablogsal commented Apr 16, 2025

Uh oh!

vstinner commented Apr 16, 2025

Uh oh!

miss-islington-app Bot commented Apr 16, 2025

Uh oh!

bedevere-app Bot commented Apr 16, 2025

Uh oh!

sergey-miryanov commented Apr 16, 2025

Uh oh!

vstinner commented Apr 17, 2025

Uh oh!

sergey-miryanov commented Apr 26, 2025

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

gh-130052: Fix search_map_for_section() error handling#132594
vstinner merged 1 commit into
python:mainfrom
vstinner:search_map

vstinner commented Apr 16, 2025 •
edited by bedevere-app Bot
Loading