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perf_jit_trampoline: mmap failure check uses wrong error value #144194

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perf_jit_trampoline: mmap failure check uses wrong error value#144194
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interpreter-core(Objects, Python, Grammar, and Parser dirs)topic-JITtype-bugAn unexpected behavior, bug, or error

Description

@stratakis
stratakis
opened on Jan 23, 2026

Bug report

Bug description:

In Python/perf_jit_trampoline.c, the perf_map_jit_init function checks for NULL to detect mmap failures, but mmap() returns MAP_FAILED (which is (void*)-1) on error, not NULL.

cpython/Python/perf_jit_trampoline.c

Line 1086 in 25a10b6

if (perf_jit_map_state.mapped_buffer == NULL) {

This means mmap failures are never detected, and jitdump initialization proceeds with an invalid pointer.

CPython versions tested on:

CPython main branch, 3.15, 3.14, 3.13

Operating systems tested on:

Linux

Linked PRs

Activity

  1. stratakis
    added
    type-bugAn unexpected behavior, bug, or error
    on Jan 23, 2026
  2. stratakis
    added a commit that references this issue on Jan 23, 2026

    pythongh-144194: Fix mmap failure check in perf_jit_trampoline.c

    40551ce
  3. StanFromIreland
    added
    interpreter-core(Objects, Python, Grammar, and Parser dirs)
    topic-JIT
    on Jan 23, 2026
  4. stratakis
    added 3 commits that reference this issue on Jan 24, 2026

    pythongh-144194: Fix mmap failure check in perf_jit_trampoline.c

    45651a9

    pythongh-144194: Fix mmap failure check in perf_jit_trampoline.c

    c2e2308

    pythongh-144194: Fix mmap failure check in perf_jit_trampoline.c

    55402f6
  5. vstinner
    added a commit that references this issue on Jan 28, 2026

    gh-144194: Fix mmap failure check in perf_jit_trampoline.c (#143713)

    8fe8a94
  6. miss-islington
    added a commit that references this issue on Jan 28, 2026

    pythongh-144194: Fix mmap failure check in perf_jit_trampoline.c (pyt…

    10f426a
  7. vstinner
    closed this as completedon Jan 28, 2026
  8. vstinner
    added 2 commits that reference this issue on Jan 28, 2026

    [3.14] gh-144194: Fix mmap failure check in perf_jit_trampoline.c (GH…

    157e946

    [3.13] gh-144194: Fix mmap failure check in perf_jit_trampoline.c (#1…

    e752ea9
  9. thunder-coding
    added a commit that references this issue on Feb 15, 2026

    pythongh-144194: Fix mmap failure check in perf_jit_trampoline.c (pyt…

    ba08ba7
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    interpreter-core(Objects, Python, Grammar, and Parser dirs)topic-JITtype-bugAn unexpected behavior, bug, or error

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