Multiboot patches

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Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Multiboot patches

# gpg: Signature made Wed 21 Mar 2018 14:38:36 GMT
# gpg:                using RSA key 7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream:
  tests/multiboot: Add .gitignore
  tests/multiboot: Add tests for the a.out kludge
  tests/multiboot: Test exit code for every qemu run
  multiboot: Check validity of mh_header_addr
  multiboot: Reject kernels exceeding the address space

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/i386/multiboot.c

@@ -229,6 +229,10 @@ int load_multiboot(FWCfgState *fw_cfg,
             error_report("invalid load_addr address");
             exit(1);
         }
+        if (mh_header_addr - mh_load_addr > i) {
+            error_report("invalid header_addr address");
+            exit(1);
+        }
 
         uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);
         uint32_t mb_load_size = 0;
@@ -247,6 +251,10 @@ int load_multiboot(FWCfgState *fw_cfg,
             }
             mb_load_size = kernel_file_size - mb_kernel_text_offset;
         }
+        if (mb_load_size > UINT32_MAX - mh_load_addr) {
+            error_report("kernel does not fit in address space");
+            exit(1);
+        }
         if (mh_bss_end_addr) {
             if (mh_bss_end_addr < (mh_load_addr + mb_load_size)) {
                 error_report("invalid bss_end_addr address");

tests/multiboot/.gitignore

@@ -0,0 +1,3 @@
+*.bin
+*.elf
+test.out

tests/multiboot/Makefile

@@ -3,16 +3,26 @@ CCFLAGS=-m32 -Wall -Wextra -Werror -fno-stack-protector -nostdinc -fno-builtin
 ASFLAGS=-m32
 
 LD=ld
-LDFLAGS=-melf_i386 -T link.ld
+LDFLAGS_ELF=-melf_i386 -T link.ld
+LDFLAGS_BIN=-melf_i386 -T link.ld --oformat=binary
 LIBS=$(shell $(CC) $(CCFLAGS) -print-libgcc-file-name)
 
-all: mmap.elf modules.elf
+AOUT_KLUDGE_BIN=$(foreach x,$(shell seq 1 9),aout_kludge_$x.bin)
 
-mmap.elf: start.o mmap.o libc.o
-	$(LD) $(LDFLAGS) -o $@ $^ $(LIBS)
+all: mmap.elf modules.elf $(AOUT_KLUDGE_BIN)
 
-modules.elf: start.o modules.o libc.o
-	$(LD) $(LDFLAGS) -o $@ $^ $(LIBS)
+mmap.elf: start.o mmap.o libc.o link.ld
+	$(LD) $(LDFLAGS_ELF) -o $@ $^ $(LIBS)
+
+modules.elf: start.o modules.o libc.o link.ld
+	$(LD) $(LDFLAGS_ELF) -o $@ $^ $(LIBS)
+
+aout_kludge_%.bin: aout_kludge_%.o link.ld
+	$(LD) $(LDFLAGS_BIN) -o $@ $^ $(LIBS)
+
+.PRECIOUS: aout_kludge_%.o
+aout_kludge_%.o: aout_kludge.S
+	$(CC) $(ASFLAGS) -DSCENARIO=$* -c -o $@ $^
 
 %.o: %.c
 	$(CC) $(CCFLAGS) -c -o $@ $^

tests/multiboot/aout_kludge.S

@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2018 Kevin Wolf <kwolf@redhat.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+.section multiboot
+
+#define MB_MAGIC 0x1badb002
+#define MB_FLAGS 0x10000
+#define MB_CHECKSUM -(MB_MAGIC + MB_FLAGS)
+
+.align  4
+.int    MB_MAGIC
+.int    MB_FLAGS
+.int    MB_CHECKSUM
+
+#define LAST_BYTE_VALUE 0xa5
+
+/*
+ * Order of fields in the a.out kludge header fields:
+ *
+ * header_addr
+ * load_addr
+ * load_end_addr
+ * bss_end_addr
+ * entry_addr
+ */
+#if SCENARIO == 1
+/* Well-behaved kernel file with explicit bss_end */
+.int    0x100000
+.int    0x100000
+.int    data_end
+.int    data_end
+.int    _start
+#elif SCENARIO == 2
+/* Well-behaved kernel file with default bss_end */
+.int    0x100000
+.int    0x100000
+.int    data_end
+.int    0
+.int    _start
+#elif SCENARIO == 3
+/* Well-behaved kernel file with default load_end */
+.int    0x100000
+.int    0x100000
+.int    0
+.int    0
+.int    _start
+#elif SCENARIO == 4
+/* Well-behaved kernel file with load_end < data_end and bss > data_end */
+#undef LAST_BYTE_VALUE
+#define LAST_BYTE_VALUE 0
+.int    0x100000
+.int    0x100000
+.int    code_end
+.int    0x140000
+.int    _start
+#elif SCENARIO == 5
+/* header < load */
+.int    0x10000
+.int    0x100000
+.int    data_end
+.int    data_end
+.int    _start
+#elif SCENARIO == 6
+/* load_end < load */
+.int    0x100000
+.int    0x100000
+.int    0x10000
+.int    data_end
+.int    _start
+#elif SCENARIO == 7
+/* header much larger than in reality with default load_end */
+.int    0x80000000
+.int    0x100000
+.int    0
+.int    data_end
+.int    _start
+#elif SCENARIO == 8
+/* bss_end < load_end - load (regression test for CVE-2018-7550) */
+.int    0x100000
+.int    0x100000
+.int    data_end
+.int    code_end
+.int    _start
+#elif SCENARIO == 9
+/* Default load_end_addr, load_addr + kernel_file_size > UINT32_MAX */
+.int    0xfffff000
+.int    0xfffff000
+.int    0
+.int    0xfffff001
+.int    _start
+#else
+#error Invalid SCENARIO
+#endif
+
+.section .text
+.global _start
+_start:
+    xor     %eax, %eax
+
+    cmpb    $LAST_BYTE_VALUE, last_byte
+    je      passed
+    or      $0x1, %eax
+passed:
+
+    /* Test device exit */
+    outl    %eax, $0xf4
+
+    cli
+    hlt
+    jmp .
+code_end:
+
+#if SCENARIO != 8
+.space 8192
+#endif
+
+last_byte:
+.byte 0xa5
+data_end:

tests/multiboot/aout_kludge.out

@@ -0,0 +1,42 @@
+
+
+
+=== Running test case: aout_kludge_1.bin  ===
+
+
+
+=== Running test case: aout_kludge_2.bin  ===
+
+
+
+=== Running test case: aout_kludge_3.bin  ===
+
+
+
+=== Running test case: aout_kludge_4.bin  ===
+
+
+
+=== Running test case: aout_kludge_5.bin  ===
+
+qemu-system-x86_64: invalid load_addr address
+
+
+=== Running test case: aout_kludge_6.bin  ===
+
+qemu-system-x86_64: invalid load_end_addr address
+
+
+=== Running test case: aout_kludge_7.bin  ===
+
+qemu-system-x86_64: invalid header_addr address
+
+
+=== Running test case: aout_kludge_8.bin  ===
+
+qemu-system-x86_64: invalid bss_end_addr address
+
+
+=== Running test case: aout_kludge_9.bin  ===
+
+qemu-system-x86_64: kernel does not fit in address space

tests/multiboot/run_test.sh

@@ -34,10 +34,21 @@ run_qemu() {
         -device isa-debugcon,chardev=stdio \
         -chardev file,path=test.out,id=stdio \
         -device isa-debug-exit,iobase=0xf4,iosize=0x4 \
-        "$@"
+        "$@" >> test.log 2>&1
     ret=$?
 
     cat test.out >> test.log
+
+    debugexit=$((ret & 0x1))
+    ret=$((ret >> 1))
+
+    if [ $debugexit != 1 ]; then
+        printf %b "\e[31m ?? \e[0m $kernel $* (no debugexit used, exit code $ret)\n"
+        pass=0
+    elif [ $ret != 0 ]; then
+        printf %b "\e[31mFAIL\e[0m $kernel $* (exit code $ret)\n"
+        pass=0
+    fi
 }
 
 mmap() {
@@ -56,24 +67,19 @@ modules() {
     run_qemu modules.elf -initrd "module.txt,module.txt argument,module.txt"
 }
 
+aout_kludge() {
+    for i in $(seq 1 9); do
+        run_qemu aout_kludge_$i.bin
+    done
+}
+
 make all
 
-for t in mmap modules; do
+for t in mmap modules aout_kludge; do
 
     echo > test.log
-    $t
-
-    debugexit=$((ret & 0x1))
-    ret=$((ret >> 1))
     pass=1
-
-    if [ $debugexit != 1 ]; then
-        printf %b "\e[31m ?? \e[0m $t (no debugexit used, exit code $ret)\n"
-        pass=0
-    elif [ $ret != 0 ]; then
-        printf %b "\e[31mFAIL\e[0m $t (exit code $ret)\n"
-        pass=0
-    fi
+    $t
 
     if ! diff $t.out test.log > /dev/null 2>&1; then
         printf %b "\e[31mFAIL\e[0m $t (output difference)\n"