Fix UB in accessing the keys#879
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clalancette merged 2 commits intorollingfrom May 3, 2026
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Doing a key.reserve() allocates memory, but still leaves the size at 0. Thus an access with the [] operator is UB. This came up on Ubuntu 26.04 because it is more strict about UB. Fix it by using resize() instead, which does increase the size and thus the [] operator is no longer UB. Signed-off-by: Chris Lalancette <clalancette@gmail.com>
The problem here is that we were always accessing 16 bytes of data from the key buffer, even when it was shorter than that. What we do instead is to always set the ihandle->value to all zeros, then only copy in the number of key_buffer bytes we have. This matches what rmw_fastrtps_cpp does, and fixes a crash in tests on Ubuntu 26.04 Signed-off-by: Chris Lalancette <clalancette@gmail.com>
This was referenced Apr 30, 2026
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Here is CI with this and all of the other PRs listed here:
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fujitatomoya
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lgtm with green CI.
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This one has ACKs and passes CI, so I'm going to merge it and backport it. |
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@Mergifyio backport lyrical kilted |
✅ Backports have been createdDetails
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This was referenced May 3, 2026
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* Make sure to do key.resize() Doing a key.reserve() allocates memory, but still leaves the size at 0. Thus an access with the [] operator is UB. This came up on Ubuntu 26.04 because it is more strict about UB. Fix it by using resize() instead, which does increase the size and thus the [] operator is no longer UB. * rmw_fastrtps_dynamic_cpp: Fix a UB in key support. The problem here is that we were always accessing 16 bytes of data from the key buffer, even when it was shorter than that. What we do instead is to always set the ihandle->value to all zeros, then only copy in the number of key_buffer bytes we have. This matches what rmw_fastrtps_cpp does, and fixes a crash in tests on Ubuntu 26.04 --------- (cherry picked from commit eb15778) Signed-off-by: Chris Lalancette <clalancette@gmail.com> Co-authored-by: Chris Lalancette <clalancette@gmail.com>
clalancette
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* Make sure to do key.resize() Doing a key.reserve() allocates memory, but still leaves the size at 0. Thus an access with the [] operator is UB. This came up on Ubuntu 26.04 because it is more strict about UB. Fix it by using resize() instead, which does increase the size and thus the [] operator is no longer UB. * rmw_fastrtps_dynamic_cpp: Fix a UB in key support. The problem here is that we were always accessing 16 bytes of data from the key buffer, even when it was shorter than that. What we do instead is to always set the ihandle->value to all zeros, then only copy in the number of key_buffer bytes we have. This matches what rmw_fastrtps_cpp does, and fixes a crash in tests on Ubuntu 26.04 --------- (cherry picked from commit eb15778) Signed-off-by: Chris Lalancette <clalancette@gmail.com> Co-authored-by: Chris Lalancette <clalancette@gmail.com>
This was referenced May 5, 2026
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Description
This fixes two different problems with respect to keys:
Doing a key.reserve() allocates memory, but still
leaves the size at 0. Thus an access with the []
operator is UB. This came up on Ubuntu 26.04 because
it is more strict about UB.
Fix it by using resize() instead, which does increase
the size and thus the [] operator is no longer UB.
The problem here is that we were always accessing 16 bytes
of data from the key buffer, even when it was shorter than
that. What we do instead is to always set the ihandle->value
to all zeros, then only copy in the number of key_buffer
bytes we have. This matches what rmw_fastrtps_cpp does,
and fixes a crash in tests on Ubuntu 26.04
This should be merged at approximately the same time as #880 , #881 , and ros2/system_tests#592
Is this user-facing behavior change?
No.
Did you use Generative AI?
Yes, Claude Opus 4.7
Additional Information
This should be backported to Lyrical and Kilted.