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[3.11] gh-105235: Prevent reading outside buffer during mmap.find() (… (#106710)

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[3.11] gh-105235: Prevent reading outside buffer during mmap.find() (GH-105252)

* Add a special case for s[-m:] == p in _PyBytes_Find

* Add tests for _PyBytes_Find

* Make sure that start <= end in mmap.find.
(cherry picked from commit ab86426a34)
This commit is contained in:
Dennis Sweeney 2023-07-14 22:17:09 -04:00 • committed by GitHub
parent 2186212191
commit d488970ae6
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5 changed files with 161 additions and 3 deletions
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21
Objects/bytesobject.c
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@ -1283,8 +1283,25 @@ _PyBytes_Find(const char *haystack, Py_ssize_t len_haystack,
const char *needle, Py_ssize_t len_needle,
Py_ssize_t offset)
{
return stringlib_find(haystack, len_haystack,
needle, len_needle, offset);
assert(len_haystack >= 0);
assert(len_needle >= 0);
// Extra checks because stringlib_find accesses haystack[len_haystack].
if (len_needle == 0) {
return offset;
}
if (len_needle > len_haystack) {
return -1;
}
assert(len_haystack >= 1);
Py_ssize_t res = stringlib_find(haystack, len_haystack - 1,
needle, len_needle, offset);
if (res == -1) {
Py_ssize_t last_align = len_haystack - len_needle;
if (memcmp(haystack + last_align, needle, len_needle) == 0) {
return offset + last_align;
}
}
return res;
}
Py_ssize_t