Re: [PATCH 0/2] util/envlist: fix prefix-match in name lookup

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Thu, May 28, 2026 at 11:24:48AM +0200, Denis V. Lunev wrote:
> On 5/20/26 23:26, Denis V. Lunev wrote:
> > A bug report against our downstream tree turned out to have its root
> > cause in plain mainstream code: envlist_unsetenv() does a prefix-match
> > lookup that drops the wrong entry when one stored name happens to be a
> > prefix of another. The downstream symptom is specific to our setup and
> > isn't interesting here -- the underlying lookup mistake is the part
> > worth fixing, and it is reachable from a normal qemu-user invocation
> > through the -U command-line option, so the fix belongs upstream.
> >
> > Patch 1 fixes the lookup: each entry now stores its name length at
> > insertion time, and a tiny helper compares with explicit length
> > equality plus memcmp. envlist_setenv()'s self-search was accidentally
> > safe (it included the '=' byte in its strncmp window and that '='
> > served as a boundary) but is converted to the same helper so the name
> > boundary becomes a structural property of the entry rather than a
> > property of its byte layout. Without that, the two sites can easily
> > drift apart again.
> >
> > Patch 2 backfils test coverage for util/envlist -- there was none --
> > in tests/unit/test-envlist. I verified that the regression case
> > (envlist_unsetenv("FOO") vs. a stored "FOOBAR=...") fails against the
> > pre-fix code and passes after the fix.
> >
> > Signed-off-by: Denis V. Lunev <den@openvz.org>
> > Cc: Stefan Hajnoczi <stefanha@redhat.com>
> > Cc: Markus Armbruster <armbru@redhat.com>
> > Cc: Paolo Bonzini <pbonzini@redhat.com>
> >
> > Denis V. Lunev (2):
> >   util/envlist: fix prefix-match in envlist_unsetenv() name lookup
> >   tests/unit: add test-envlist covering setenv/unsetenv name matching
> >
> >  tests/unit/meson.build    |   1 +
> >  tests/unit/test-envlist.c | 196 ++++++++++++++++++++++++++++++++++++++
> >  util/envlist.c            |  19 +++-
> >  3 files changed, 212 insertions(+), 4 deletions(-)
> >  create mode 100644 tests/unit/test-envlist.c
> >

I will way until Wednesday to merge this so that the -user maintainers
have a chance to take a look:

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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