[Qemu-devel] [PULL 0/5] Multiboot patches

[Qemu-devel] [PULL 0/5] Multiboot patches

[Kevin Wolf]

The following changes since commit f1a63fcfcd92c88be8942b5ae71aef9749a4f135:

  Update version for v2.12.0-rc0 release (2018-03-20 19:04:22 +0000)

are available in the git repository at:

  git://repo.or.cz/qemu/kevin.git tags/for-upstream

for you to fetch changes up to e2679395d598bd40770c22a793c0152576ac211f:

  tests/multiboot: Add .gitignore (2018-03-21 15:13:40 +0100)

----------------------------------------------------------------
Multiboot patches

----------------------------------------------------------------
Kevin Wolf (5):
      multiboot: Reject kernels exceeding the address space
      multiboot: Check validity of mh_header_addr
      tests/multiboot: Test exit code for every qemu run
      tests/multiboot: Add tests for the a.out kludge
      tests/multiboot: Add .gitignore

 hw/i386/multiboot.c             |   8 +++
 tests/multiboot/.gitignore      |   3 +
 tests/multiboot/Makefile        |  22 +++++--
 tests/multiboot/aout_kludge.S   | 138 ++++++++++++++++++++++++++++++++++++++++
 tests/multiboot/aout_kludge.out |  42 ++++++++++++
 tests/multiboot/run_test.sh     |  34 ++++++----
 6 files changed, 227 insertions(+), 20 deletions(-)
 create mode 100644 tests/multiboot/.gitignore
 create mode 100644 tests/multiboot/aout_kludge.S
 create mode 100644 tests/multiboot/aout_kludge.out

[Qemu-devel] [PULL 1/5] multiboot: Reject kernels exceeding the address space

[Kevin Wolf]

The code path where mh_load_end_addr is non-zero in the Multiboot
header checks that mh_load_end_addr >= mh_load_addr and so
mb_load_size is checked.  However, mb_load_size is not checked when
calculated from the file size, when mh_load_end_addr is 0.

If the kernel binary size is larger than can fit in the address space
after load_addr, we ended up with a kernel_size that is smaller than
load_size, which means that we read the file into a too small buffer.

Add a check to reject kernel files with such Multiboot headers.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jack Schwartz <jack.schwartz@oracle.com>
---
 hw/i386/multiboot.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
index b9064264d8..1e215bf8d3 100644
--- a/hw/i386/multiboot.c
+++ b/hw/i386/multiboot.c
@@ -247,6 +247,10 @@ 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");
-- 
2.13.6

[Qemu-devel] [PULL 2/5] multiboot: Check validity of mh_header_addr

[Kevin Wolf]

I couldn't find a case where this prevents something bad from happening
that isn't already caught by other checks, but let's err on the safe
side and check that mh_header_addr is as expected.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jack Schwartz <jack.schwartz@oracle.com>
---
 hw/i386/multiboot.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
index 1e215bf8d3..5bc0a2cddb 100644
--- a/hw/i386/multiboot.c
+++ b/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;
-- 
2.13.6

[Qemu-devel] [PULL 3/5] tests/multiboot: Test exit code for every qemu run

[Kevin Wolf]

Testing the exit code only once after a whole group of tests has
completed is not enough, it catches errors only in the very last qemu
invocation. We need to have the check after each qemu run.

The logging and diff with the reference output is still done once per
group to keep things more managable. This is not a problem because the
log file accumulates the output of all runs.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jack Schwartz <jack.schwartz@oracle.com>
---
 tests/multiboot/run_test.sh | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/tests/multiboot/run_test.sh b/tests/multiboot/run_test.sh
index 0278148b43..bc9c3670af 100755
--- a/tests/multiboot/run_test.sh
+++ b/tests/multiboot/run_test.sh
@@ -38,6 +38,17 @@ run_qemu() {
     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() {
@@ -61,19 +72,8 @@ make all
 for t in mmap modules; 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"
-- 
2.13.6

[Qemu-devel] [PULL 4/5] tests/multiboot: Add tests for the a.out kludge

[Kevin Wolf]

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jack Schwartz <jack.schwartz@oracle.com>
---
 tests/multiboot/Makefile        |  22 +++++--
 tests/multiboot/aout_kludge.S   | 138 ++++++++++++++++++++++++++++++++++++++++
 tests/multiboot/aout_kludge.out |  42 ++++++++++++
 tests/multiboot/run_test.sh     |  10 ++-
 4 files changed, 204 insertions(+), 8 deletions(-)
 create mode 100644 tests/multiboot/aout_kludge.S
 create mode 100644 tests/multiboot/aout_kludge.out

diff --git a/tests/multiboot/Makefile b/tests/multiboot/Makefile
index 36f01dc647..ed4225e7d1 100644
--- a/tests/multiboot/Makefile
+++ b/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 $@ $^
diff --git a/tests/multiboot/aout_kludge.S b/tests/multiboot/aout_kludge.S
new file mode 100644
index 0000000000..52e8ebd766
--- /dev/null
+++ b/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, $0xf4
+
+    cli
+    hlt
+    jmp .
+code_end:
+
+#if SCENARIO != 8
+.space 8192
+#endif
+
+last_byte:
+.byte 0xa5
+data_end:
diff --git a/tests/multiboot/aout_kludge.out b/tests/multiboot/aout_kludge.out
new file mode 100644
index 0000000000..031459275b
--- /dev/null
+++ b/tests/multiboot/aout_kludge.out
@@ -0,0 +1,42 @@
+
+
+
+=== Running test case: aout_kludge_1.bin  ===
+
+
+
+=== Running test case: aout_kludge_2.bin  ===
+
+
+
+=== Running test case: aout_kludge_3.bin  ===
+
+
+
+=== Running test case: aout_kludge_4.bin  ===
+
+
+
+=== Running test case: aout_kludge_5.bin  ===
+
+qemu-system-x86_64: invalid load_addr address
+
+
+=== Running test case: aout_kludge_6.bin  ===
+
+qemu-system-x86_64: invalid load_end_addr address
+
+
+=== Running test case: aout_kludge_7.bin  ===
+
+qemu-system-x86_64: invalid header_addr address
+
+
+=== Running test case: aout_kludge_8.bin  ===
+
+qemu-system-x86_64: invalid bss_end_addr address
+
+
+=== Running test case: aout_kludge_9.bin  ===
+
+qemu-system-x86_64: kernel does not fit in address space
diff --git a/tests/multiboot/run_test.sh b/tests/multiboot/run_test.sh
index bc9c3670af..6c33003e71 100755
--- a/tests/multiboot/run_test.sh
+++ b/tests/multiboot/run_test.sh
@@ -34,7 +34,7 @@ run_qemu() {
         -device isa-debugcon,chardev=stdio \
         -chardev file,path=test.out,id=stdio \
         -device isa-debug-exit,iobase=0xf4,iosize=0x4 \
-        "$@"
+        "$@" >> test.log 2>&1
     ret=$?
 
     cat test.out >> test.log
@@ -67,9 +67,15 @@ 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
     pass=1
-- 
2.13.6

[Qemu-devel] [PULL 5/5] tests/multiboot: Add .gitignore

[Kevin Wolf]

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jack Schwartz <jack.schwartz@oracle.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
---
 tests/multiboot/.gitignore | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 tests/multiboot/.gitignore

diff --git a/tests/multiboot/.gitignore b/tests/multiboot/.gitignore
new file mode 100644
index 0000000000..93ef99800b
--- /dev/null
+++ b/tests/multiboot/.gitignore
@@ -0,0 +1,3 @@
+*.bin
+*.elf
+test.out
-- 
2.13.6

Re: [Qemu-devel] [PULL 0/5] Multiboot patches

[Peter Maydell]

On 21 March 2018 at 14:41, Kevin Wolf <kwolf@redhat.com> wrote:
> The following changes since commit f1a63fcfcd92c88be8942b5ae71aef9749a4f135:
>
>   Update version for v2.12.0-rc0 release (2018-03-20 19:04:22 +0000)
>
> are available in the git repository at:
>
>   git://repo.or.cz/qemu/kevin.git tags/for-upstream
>
> for you to fetch changes up to e2679395d598bd40770c22a793c0152576ac211f:
>
>   tests/multiboot: Add .gitignore (2018-03-21 15:13:40 +0100)
>
> ----------------------------------------------------------------
> Multiboot patches
>
> ----------------------------------------------------------------
> Kevin Wolf (5):
>       multiboot: Reject kernels exceeding the address space
>       multiboot: Check validity of mh_header_addr
>       tests/multiboot: Test exit code for every qemu run
>       tests/multiboot: Add tests for the a.out kludge
>       tests/multiboot: Add .gitignore

Applied, thanks.

-- PMM