Fix invalid access in lpFind on corrupted listpack (#9819)

Issue found by corrupt-dump-fuzzer test with ASAN.
The problem was that lpSkip and lpGetWithSize could read the next listpack entry without validating that it's in range.
Similarly even the memcmp in lpFind could do that and possibly crash on segfault and now they'll crash on assert first.

The naive fix of using lpAssertValidEntry every time, resulted in 30% degradation in the lpFind benchmark of the unit test.
The final fix with the condition at the bottom has no performance implications.

2 files changed, 18 insertions, 1 deletions

diff --git a/src/listpack.c b/src/listpack.c
index d876751e5..0d91cb55b 100644
--- a/src/listpack.c
+++ b/src/listpack.c
@@ -699,6 +699,8 @@ unsigned char *lpFind(unsigned char *lp, unsigned char *p, unsigned char *s,
         if (skipcnt == 0) {
             value = lpGetWithSize(p, &ll, NULL, &entry_size);
             if (value) {
+                /* check the value doesn't reach outside the listpack before accessing it */
+                assert(p >= lp + LP_HDR_SIZE && p + entry_size < lp + lp_bytes);
                 if (slen == ll && memcmp(value, s, slen) == 0) {
                     return p;
                 }
@@ -737,7 +739,12 @@ unsigned char *lpFind(unsigned char *lp, unsigned char *p, unsigned char *s,
             p = lpSkip(p);
         }
 
-        assert(p >= lp + LP_HDR_SIZE && p < lp + lp_bytes);
+        /* The next call to lpGetWithSize could read at most 8 bytes past `p`
+         * We use the slower validation call only when necessary. */
+        if (p + 8 >= lp + lp_bytes)
+            lpAssertValidEntry(lp, lp_bytes, p);
+        else
+            assert(p >= lp + LP_HDR_SIZE && p < lp + lp_bytes);
         if (p[0] == LP_EOF) break;
     }
 
diff --git a/tests/integration/corrupt-dump.tcl b/tests/integration/corrupt-dump.tcl
index 0b085510f..995ba7934 100644
--- a/tests/integration/corrupt-dump.tcl
+++ b/tests/integration/corrupt-dump.tcl
@@ -764,5 +764,15 @@ test {corrupt payload: fuzzer findings - gcc asan reports false leak on assert}
     }
 }
 
+test {corrupt payload: fuzzer findings - lpFind invalid access } {
+    start_server [list overrides [list loglevel verbose use-exit-on-panic yes crash-memcheck-enabled no] ] {
+        r debug set-skip-checksum-validation 1
+        r config set sanitize-dump-payload no
+         r restore _hashbig 0 "\x10\x39\x39\x00\x00\x00\x14\x00\x06\x01\x06\x01\x03\x01\x82\x5F\x33\x03\x07\x01\x82\x5F\x37\x03\x00\x01\x00\x01\x04\x01\x04\x01\x09\x01\x82\x5F\x39\x03\x05\x01\x82\x5F\x35\x03\x08\x01\x08\x01\x01\x01\x82\x5F\x31\x03\x02\x01\xF0\x01\xFF\x0A\x00\x29\xD7\xE4\x52\x79\x7A\x95\x82"
+         catch { r HLEN _hashbig }
+         catch { r HSETNX _hashbig 513072881620 "\x9A\x4B\x1F\xF2\x99\x74\x6E\x96\x84\x7F\xB9\x85\xBE\xD6\x1A\x93\x0A\xED\xAE\x19\xA0\x5A\x67\xD6\x89\xA8\xF9\xF2\xB8\xBD\x3E\x5A\xCF\xD2\x5B\x17\xA4\xBB\xB2\xA9\x56\x67\x6E\x0B\xED\xCD\x36\x49\xC6\x84\xFF\xC2\x76\x9B\xF3\x49\x88\x97\x92\xD2\x54\xE9\x08\x19\x86\x40\x96\x24\x68\x25\x9D\xF7\x0E\xB7\x36\x85\x68\x6B\x2A\x97\x64\x30\xE6\xFF\x9A\x2A\x42\x2B\x31\x01\x32\xB3\xEE\x78\x1A\x26\x94\xE2\x07\x34\x50\x8A\xFF\xF9\xAE\xEA\xEC\x59\x42\xF5\x39\x40\x65\xDE\x55\xCC\x77\x1B\x32\x02\x19\xEE\x3C\xD4\x79\x48\x01\x4F\x51\xFE\x22\xE0\x0C\xF4\x07\x06\xCD\x55\x30\xC0\x24\x32\xD4\xCC\xAF\x82\x05\x48\x14\x10\x55\xA1\x3D\xF6\x81\x45\x54\xEA\x71\x24\x27\x06\xDC\xFA\xE4\xE4\x87\xCC\x81\xA0\x47\xA5\xAF\xD1\x89\xE7\x42\xC3\x24\xD0\x32\x7A\xDE\x44\x47\x6E\x1F\xCB\xEE\xA6\x46\xDE\x0D\xE6\xD5\x16\x03\x2A\xD6\x9E\xFD\x94\x02\x2C\xDB\x1F\xD0\xBE\x98\x10\xE3\xEB\xEA\xBE\xE5\xD1" }
+    }
+}
+
 } ;# tags