Fix/memdump off by one (#1870)

* fix/memdump off by one

* log real unaligned dump addr

---------

Co-authored-by: Pawel Solowiej <pawelsol@cert.pl>

Author: psolvx

src/plugins/memdump/memdump.cpp

@@ -187,10 +187,9 @@ bool dump_memory_region(
 
     const gchar* chk_str = nullptr;
 
+    addr_t dump_addr = ctx->addr;
     addr_t aligned_addr;
     addr_t intra_page_offset;
-    size_t aligned_len;
-    size_t len_remainder;
     size_t num_pages;
 
     GChecksum* checksum = nullptr;
@@ -213,16 +212,9 @@ bool dump_memory_region(
     aligned_addr = ctx->addr & ~(VMI_PS_4KB - 1);
     intra_page_offset = ctx->addr & (VMI_PS_4KB - 1);
 
-    aligned_len = len_bytes & ~(VMI_PS_4KB - 1);
-    len_remainder = len_bytes & (VMI_PS_4KB - 1);
-
-    if (len_remainder)
-    {
-        aligned_len += VMI_PS_4KB;
-    }
+    num_pages = (intra_page_offset + len_bytes + VMI_PS_4KB - 1) / VMI_PS_4KB;
 
     ctx->addr = aligned_addr;
-    num_pages = aligned_len / VMI_PS_4KB;
 
     access_ptrs = (void**)g_malloc(num_pages * sizeof(void*));
 
@@ -284,7 +276,7 @@ bool dump_memory_region(
     // * de-duplication - sometimes, different heuristics may want to dump the same piece of memory;
     //   unless there is a change in image base or contents, repeated memory dumps would get exactly
     //   the same file name
-    if (asprintf(&file, "%llx_%.16s", (unsigned long long) ctx->addr, chk_str) < 0)
+    if (asprintf(&file, "%llx_%.16s", (unsigned long long) dump_addr, chk_str) < 0)
         goto done;
 
     if (asprintf(&file_path, "%s/%s", plugin->memdump_dir, file) < 0)
@@ -298,7 +290,7 @@ bool dump_memory_region(
     if (asprintf(&metafile, "%s/memdump.%06d", plugin->memdump_dir, sequence_number) < 0)
         goto done;
 
-    save_file_metadata(info, metafile, file, len_bytes, ctx->addr, info->trap->name, reason, sequence_number, extras);
+    save_file_metadata(info, metafile, file, len_bytes, dump_addr, info->trap->name, reason, sequence_number, extras);
 
     ret = true;
 
@@ -309,7 +301,7 @@ bool dump_memory_region(
         auto default_print = std::make_tuple(
                 keyval("DumpReason", fmt::Qstr(reason)),
                 keyval("DumpPID", fmt::Nval(info->attached_proc_data.pid)),
-                keyval("DumpAddr", fmt::Xval(ctx->addr, false)),
+                keyval("DumpAddr", fmt::Xval(dump_addr, false)),
                 keyval("DumpSize", fmt::Xval(len_bytes)),
                 keyval("DumpFilename", fmt::Qstr(display_file)),
                 keyval("DumpsCount", fmt::Nval(sequence_number))