Fix undefined behavior: invalid access of NULL ptr. #197
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
Found with msan/asan analysis. Signed-off-by: Henner Zeller <[email protected]>
hzeller
force-pushed
the
20221121-fix-invalid-null-access
branch
from
c30e56e to
c39a501
Compare
|
With UBSAN, actually! It's UB to a) shift signed ints too much, and b) do non-trivial arithmetic on null pointers |
tkoeppe
reviewed
Nov 21, 2022
Comment on lines
+99
to
+111
| if ( p->pPars->fTruth ) | ||
| { | ||
| p->puTemp[0] = p->pPars->fTruth? ABC_ALLOC( unsigned, 8 * p->nTruth6Words[p->pPars->nLutSize] ) : NULL; | ||
| p->puTemp[1] = p->puTemp[0] + p->nTruth6Words[p->pPars->nLutSize]*2; | ||
| p->puTemp[2] = p->puTemp[1] + p->nTruth6Words[p->pPars->nLutSize]*2; | ||
| p->puTemp[3] = p->puTemp[2] + p->nTruth6Words[p->pPars->nLutSize]*2; | ||
| p->puTempW = p->pPars->fTruth? ABC_ALLOC( word, p->nTruth6Words[p->pPars->nLutSize] ) : NULL; | ||
| } | ||
| else | ||
| { | ||
| p->puTemp[0] = p->puTemp[1] = p->puTemp[2] = p->puTemp[3] = NULL; | ||
| p->puTempW = NULL; | ||
| } |
There was a problem hiding this comment.
I would welcome a somewhat careful review of this change. It wasn't immediately clear to me if in the case of !p->pPars->fTruth the various p->pu* pointers are actually unused. This case currently has undefined behaviour, but maybe there's some obscure pointer-to-offset logic somewhere else that actually needed those "null pointer increments"?
tkoeppe
reviewed
Nov 21, 2022
| if (quit) { | ||
| break; | ||
| } else { | ||
| path = ++cp; |
There was a problem hiding this comment.
The same mistake fixed twice in this patch: the increment must not happen after the last round of the loop.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
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.
Found with msan analysis.