From 2383c6015c511e6af2ce032593dee10972b12373 Mon Sep 17 00:00:00 2001 From: Duane Griffin Date: Mon, 14 Jul 2025 21:50:22 +1200 Subject: [PATCH] [3.13] gh-127971: fix off-by-one read beyond the end of a string during search (#132574) (#136648) (cherry picked from commit 85ec3b3b503ffd5b7e45f8b3fa2cec0c10e4bef0) --- Lib/test/string_tests.py | 9 +++++++++ .../2025-04-16-12-01-13.gh-issue-127971.pMDOQ0.rst | 1 + Objects/stringlib/fastsearch.h | 8 ++++---- 3 files changed, 14 insertions(+), 4 deletions(-) create mode 100644 Misc/NEWS.d/next/Core and Builtins/2025-04-16-12-01-13.gh-issue-127971.pMDOQ0.rst diff --git a/Lib/test/string_tests.py b/Lib/test/string_tests.py index 9bb0ce7bb57..8dcfa98f85b 100644 --- a/Lib/test/string_tests.py +++ b/Lib/test/string_tests.py @@ -767,6 +767,15 @@ class BaseTest: self.checkraises(TypeError, 'hello', 'replace', 42, 'h') self.checkraises(TypeError, 'hello', 'replace', 'h', 42) + def test_replacement_on_buffer_boundary(self): + # gh-127971: Check we don't read past the end of the buffer when a + # potential match misses on the last character. + any_3_nonblank_codepoints = '!!!' + seven_codepoints = any_3_nonblank_codepoints + ' ' + any_3_nonblank_codepoints + a = (' ' * 243) + seven_codepoints + (' ' * 7) + b = ' ' * 6 + chr(256) + a.replace(seven_codepoints, b) + def test_replace_uses_two_way_maxcount(self): # Test that maxcount works in _two_way_count in fastsearch.h A, B = "A"*1000, "B"*1000 diff --git a/Misc/NEWS.d/next/Core and Builtins/2025-04-16-12-01-13.gh-issue-127971.pMDOQ0.rst b/Misc/NEWS.d/next/Core and Builtins/2025-04-16-12-01-13.gh-issue-127971.pMDOQ0.rst new file mode 100644 index 00000000000..ced7a9c9fd3 --- /dev/null +++ b/Misc/NEWS.d/next/Core and Builtins/2025-04-16-12-01-13.gh-issue-127971.pMDOQ0.rst @@ -0,0 +1 @@ +Fix off-by-one read beyond the end of a string in string search. diff --git a/Objects/stringlib/fastsearch.h b/Objects/stringlib/fastsearch.h index 257b7bd6788..513250c08be 100644 --- a/Objects/stringlib/fastsearch.h +++ b/Objects/stringlib/fastsearch.h @@ -588,7 +588,7 @@ STRINGLIB(default_find)(const STRINGLIB_CHAR* s, Py_ssize_t n, continue; } /* miss: check if next character is part of pattern */ - if (!STRINGLIB_BLOOM(mask, ss[i+1])) { + if (i + 1 <= w && !STRINGLIB_BLOOM(mask, ss[i+1])) { i = i + m; } else { @@ -597,7 +597,7 @@ STRINGLIB(default_find)(const STRINGLIB_CHAR* s, Py_ssize_t n, } else { /* skip: check if next character is part of pattern */ - if (!STRINGLIB_BLOOM(mask, ss[i+1])) { + if (i + 1 <= w && !STRINGLIB_BLOOM(mask, ss[i+1])) { i = i + m; } } @@ -661,7 +661,7 @@ STRINGLIB(adaptive_find)(const STRINGLIB_CHAR* s, Py_ssize_t n, } } /* miss: check if next character is part of pattern */ - if (!STRINGLIB_BLOOM(mask, ss[i+1])) { + if (i + 1 <= w && !STRINGLIB_BLOOM(mask, ss[i+1])) { i = i + m; } else { @@ -670,7 +670,7 @@ STRINGLIB(adaptive_find)(const STRINGLIB_CHAR* s, Py_ssize_t n, } else { /* skip: check if next character is part of pattern */ - if (!STRINGLIB_BLOOM(mask, ss[i+1])) { + if (i + 1 <= w && !STRINGLIB_BLOOM(mask, ss[i+1])) { i = i + m; } }