bpo-35193: Fix an off by one error in the RETURN_VALUE case. #10418
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
By doing a bounds check within find_op so it can return before going past the end as a safety measure. python@7db3c48#diff-a33329ae6ae0bb295d742f0caf93c137 introduced this off by one error while fixing another one nearby.
gpshead
added
type-bug
| @@ -417,7 +419,7 @@ PyCode_Optimize(PyObject *code, PyObject* consts, PyObject *names, | |||
| } | |||
| if (h > i + 1) { | |||
| fill_nops(codestr, i + 1, h); | |||
| nexti = find_op(codestr, h); | |||
There was a problem hiding this comment.
Wouldn't be simpler to just add a condition in this line?
nexti = (h < codelen) ? find_op(codestr, h) : codelen;
There was a problem hiding this comment.
That would leave room for the same bug to be introduced in other calls to find_op.
There was a problem hiding this comment.
In other calls find_op() can't be called with codelen.
There was a problem hiding this comment.
Yes. That's why I said "introduced". this prevents the bug from reappearing when the rest of the code changes.
Yhg1s
approved these changes
Nov 8, 2018
I don't see how to test for the presence of this out of bounds memory access issue itself from the level of the CPython interpreter, but this test will reliably fail (crash) when the interpreter is built using the clang memory sanitizer.
Yhg1s
approved these changes
Nov 9, 2018
| Fix an off by one error in the bytecode peephole optimizer where it could read | ||
| bytes beyond the end of bounds of a bytecode array when removing unreachable | ||
| code after a return. This did not always crash an interpreter, but could. | ||
| An interpreter compiled using the clang memory sanitizer always failed. |
There was a problem hiding this comment.
This seems a little longer and more detailed than most news entries... not sure if that's good or bad.
|
Thanks @gpshead for the PR 🌮🎉.. I'm working now to backport this PR to: 3.6, 3.7. |
|
GH-10421 is a backport of this pull request to the 3.7 branch. |
|
Sorry, @gpshead, I could not cleanly backport this to |
miss-islington
pushed a commit
to miss-islington/cpython
that referenced
this pull request
Nov 9, 2018
…H-10418) Fix an off by one error in the peephole optimizer when checking for unreachable code beyond a return. Do a bounds check within find_op so it can return before going past the end as a safety measure. python@7db3c488335168993689ddae5914a28e16188447GH-diff-a33329ae6ae0bb295d742f0caf93c137 introduced this off by one error while fixing another one nearby. This bug was shipped in all Python 3.6 and 3.7 releases. The included unittest won't fail unless you do a clang msan build. (cherry picked from commit 49fa4a9) Co-authored-by: Gregory P. Smith <greg@krypto.org>
miss-islington
added a commit
that referenced
this pull request
Nov 9, 2018
Fix an off by one error in the peephole optimizer when checking for unreachable code beyond a return. Do a bounds check within find_op so it can return before going past the end as a safety measure. 7db3c488335168993689ddae5914a28e16188447GH-diff-a33329ae6ae0bb295d742f0caf93c137 introduced this off by one error while fixing another one nearby. This bug was shipped in all Python 3.6 and 3.7 releases. The included unittest won't fail unless you do a clang msan build. (cherry picked from commit 49fa4a9) Co-authored-by: Gregory P. Smith <greg@krypto.org>
gpshead
added a commit
to gpshead/cpython
that referenced
this pull request
Nov 9, 2018
…H-10418) Fix an off by one error in the peephole optimizer when checking for unreachable code beyond a return. Do a bounds check within find_op so it can return before going past the end as a safety measure. python@7db3c48#diff-a33329ae6ae0bb295d742f0caf93c137 introduced this off by one error while fixing another one nearby. This bug was shipped in all Python 3.6 and 3.7 releases. The included unittest won't fail unless you do a clang msan build. (cherry picked from commit 49fa4a9)
|
GH-10422 is a backport of this pull request to the 3.6 branch. |
gpshead
added a commit
that referenced
this pull request
Nov 9, 2018
… (GH-10422) Fix an off by one error in the peephole optimizer when checking for unreachable code beyond a return. Do a bounds check within find_op so it can return before going past the end as a safety measure. 7db3c48#diff-a33329ae6ae0bb295d742f0caf93c137 introduced this off by one error while fixing another one nearby. This bug was shipped in all Python 3.6 and 3.7 releases. The included unittest won't fail unless you do a clang msan build. (cherry picked from commit 49fa4a9)
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
By doing a bounds check within find_op so it can
return before going past the end as a safety measure.
7db3c48#diff-a33329ae6ae0bb295d742f0caf93c137
introduced this off by one error while fixing another one nearby.
https://bugs.python.org/issue35193