Merge bitcoin/bitcoin#24312: addrman: Log too low compat value

fa097d074bc1afcc2a52976796bb618f7c6a68b3 addrman: Log too low compat value (MarcoFalke)

Pull request description:

  Before this patch, when writing a negative `lowest_compatible` value, it would be read as a positive value. For example `-32` will be read as `224`. There is generally nothing wrong with that. Though, similarly there shouldn't be anything wrong with refusing to read a negative value. I find the code after this patch more logical than before. Also, this allows dropping a file-wide sanitizer suppression.

  In practice none of this should ever happen. Bitcoin Core would never write a negative `lowest_compatible` in normal operation, unless the file storage is later corrupted by external influence.

ACKs for top commit:
  mzumsande:
    re-ACK fa097d074bc1afcc2a52976796bb618f7c6a68b3

Tree-SHA512: 9aae7b8fe666f52f667f149667025e0160cef1a793cc4d392e36608f65c2bee8096da429235118f40a3368f327aabe30f3732ae78c5874648ea6f423f2687b65

1 files changed, 7 insertions, 1 deletions

diff --git a/src/addrman.cpp b/src/addrman.cpp
index f91a979934..2fd8143c1c 100644
--- a/src/addrman.cpp
+++ b/src/addrman.cpp
@@ -246,12 +246,18 @@ void AddrManImpl::Unserialize(Stream& s_)
 
     uint8_t compat;
     s >> compat;
+    if (compat < INCOMPATIBILITY_BASE) {
+        throw std::ios_base::failure(strprintf(
+            "Corrupted addrman database: The compat value (%u) "
+            "is lower than the expected minimum value %u.",
+            compat, INCOMPATIBILITY_BASE));
+    }
     const uint8_t lowest_compatible = compat - INCOMPATIBILITY_BASE;
     if (lowest_compatible > FILE_FORMAT) {
         throw InvalidAddrManVersionError(strprintf(
             "Unsupported format of addrman database: %u. It is compatible with formats >=%u, "
             "but the maximum supported by this version of %s is %u.",
-            uint8_t{format}, uint8_t{lowest_compatible}, PACKAGE_NAME, uint8_t{FILE_FORMAT}));
+            uint8_t{format}, lowest_compatible, PACKAGE_NAME, uint8_t{FILE_FORMAT}));
     }
 
     s >> nKey;