libfec: correct verity table only if it's invalid

To increase reliability in the case where part of the partition is
corrupt and error correction might fail, attempt to use raw verity
table before the corrected one.

Bug: 32288104
Test: tested on angler
Change-Id: I201fdc6162c87b1808979486df5707d683a6d20c

1 files changed, 28 insertions, 4 deletions

diff --git a/libfec/fec_verity.cpp b/libfec/fec_verity.cpp
index 5dea53dd..3f636dd0 100644
--- a/libfec/fec_verity.cpp
+++ b/libfec/fec_verity.cpp
@@ -312,6 +312,11 @@ static int verify_tree(fec_handle *f, const uint8_t *root)
 
     debug("valid");
 
+    if (v->hash) {
+        delete[] v->hash;
+        v->hash = NULL;
+    }
+
     v->hash = data_hashes.release();
     return 0;
 }
@@ -319,7 +324,7 @@ static int verify_tree(fec_handle *f, const uint8_t *root)
 /* reads, corrects and parses the verity table, validates parameters, and if
    `f->flags' does not have `FEC_VERITY_DISABLE' set, calls `verify_tree' to
    load and validate the hash tree */
-static int parse_table(fec_handle *f, uint64_t offset, uint32_t size)
+static int parse_table(fec_handle *f, uint64_t offset, uint32_t size, bool useecc)
 {
     check(f);
     check(size >= VERITY_MIN_TABLE_SIZE);
@@ -335,8 +340,13 @@ static int parse_table(fec_handle *f, uint64_t offset, uint32_t size)
         return -1;
     }
 
-    if (fec_pread(f, table.get(), size, offset) != (ssize_t)size) {
-        error("failed to read verity table: %s", strerror(errno));
+    if (!useecc) {
+        if (!raw_pread(f, table.get(), size, offset)) {
+            error("failed to read verity table: %s", strerror(errno));
+            return -1;
+        }
+    } else if (fec_pread(f, table.get(), size, offset) != (ssize_t)size) {
+        error("failed to ecc read verity table: %s", strerror(errno));
         return -1;
     }
 
@@ -430,7 +440,18 @@ static int parse_table(fec_handle *f, uint64_t offset, uint32_t size)
         check(v->data_blocks == v->hash_start / FEC_BLOCKSIZE);
     }
 
+    if (v->salt) {
+        delete[] v->salt;
+        v->salt = NULL;
+    }
+
     v->salt = salt.release();
+
+    if (v->table) {
+        delete[] v->table;
+        v->table = NULL;
+    }
+
     v->table = table.release();
 
     if (!(f->flags & FEC_VERITY_DISABLE)) {
@@ -589,7 +610,10 @@ int verity_parse_header(fec_handle *f, uint64_t offset)
 
     v->metadata_start = offset;
 
-    if (parse_table(f, offset + sizeof(v->header), v->header.length) == -1) {
+    if (parse_table(f, offset + sizeof(v->header), v->header.length,
+            false) == -1 &&
+        parse_table(f, offset + sizeof(v->header), v->header.length,
+            true)  == -1) {
         return -1;
     }