Hi Jan,
On 08/11/2023 11:19, Jan Beulich wrote:
On 08.11.2023 12:03, Nicola Vetrini wrote:
On 2023-11-08 09:24, Jan Beulich wrote:
On 03.11.2023 18:58, Nicola Vetrini wrote:
Static analysis tools may detect a possible null
pointer dereference at line 760 (the memcpy call)
of xen/common/domain.c. This ASSERT helps them in
detecting that such a condition is not possible
and also provides a basic sanity check.
I disagree with this being a possible justification for adding such a
redundant assertion. More detail is needed on what is actually
(suspected to be) confusing the tool. Plus it also needs explaining
why (a) adding such an assertion helps and (b) how that's going to
cover release builds.
How about:
"Static analysis tools may detect a possible null pointer dereference
at line 760 (config->handle) due to config possibly being NULL.
However, given that all system domains, including IDLE, have a NULL
config and in the code path leading to the assertion only real domains
(which have a non-NULL config) can be present."
On point b): this finding is a false positive, therefore even if the
ASSERT is
expanded to effectively a no-op, there is no inherent problem with Xen's
code.
The context in which the patch was suggested [1] hinted at avoiding
inserting in
the codebase false positive comments.
Which I largely agree with. What I don't agree with is adding an
assertion which is only papering over the issue, and only in debug
builds.
I expect that the number of issues will increase a lot as soon as we
start to analyze production builds.
I don't think it will be a solution to either replace all the ASSERT()
with runtime check in all configuration or even...
So perhaps instead we need a different way of tracking
false positives (which need to be tied to specific checker versions
anyway).
... documenting false positive.
IMHO, the only viable option would be to have a configuration to keep
ASSERT in production build for scanning tools.
Cheers,
--
Julien Grall
