[PULL,3/5] migration: Assert that migrate_multifd_compression() returns an in-range value

Commit Message

Dr. David Alan Gilbert Aug. 2, 2022, 3:54 p.m. UTC

From: Peter Maydell <[e-mail]>

Coverity complains that when we use the return value from
migrate_multifd_compression() as an array index:
  multifd_recv_state->ops = multifd_ops[migrate_multifd_compression()];

that this might overrun the array (which is declared to have size
MULTIFD_COMPRESSION__MAX).  This is because the function return type
is MultiFDCompression, which is an autogenerated enum.  The code
generator includes the "one greater than the maximum possible value"
MULTIFD_COMPRESSION__MAX in the enum, even though this is not
actually a valid value for the enum, and this makes Coverity think
that migrate_multifd_compression() could return that __MAX value and
index off the end of the array.

Suppress the Coverity error by asserting that the value we're going
to return is within range.

Resolves: Coverity CID 1487239, 1487254
Signed-off-by: Peter Maydell <[e-mail]>
Message-Id: <[e-mail]>
Reviewed-by: Dr. David Alan Gilbert <[e-mail]>
Reviewed-by: Juan Quintela <[e-mail]>
Signed-off-by: Dr. David Alan Gilbert <[e-mail]>
---
 migration/migration.c | 1 +
 1 file changed, 1 insertion(+)

Patch

diff --git a/migration/migration.c b/migration/migration.c
index 82fbe0cf55..bb8bbddfe4 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2617,6 +2617,7 @@  MultiFDCompression migrate_multifd_compression(void)
 
     s = migrate_get_current();
 
+    assert(s->parameters.multifd_compression < MULTIFD_COMPRESSION__MAX);
     return s->parameters.multifd_compression;
 }