[Qemu-devel] [PATCH] linux-user: check valid address in access_ok()

[Laurent Vivier <lvivier@redhat.com>]

From: Rémi Denis-Courmont <remi@remlab.net>

Fix a crash with LTP testsuite and aarch64:

  tst_test.c:1015: INFO: Timeout per run is 0h 05m 00s
  qemu-aarch64: .../qemu/accel/tcg/translate-all.c:2522: page_check_range: Assertion `start < ((target_ulong)1 << L1_MAP_ADDR_SPACE_BITS)' failed.
  qemu:handle_cpu_signal received signal outside vCPU context @ pc=0x60001554

page_check_range() should never be called with address outside the guest
address space. This patch adds a guest_addr_valid() check in access_ok()
to only call page_check_range() with a valid address.

Fixes: f6768aa1b4c6 ("target/arm: fix AArch64 virtual address space size")
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---

Notes:
    v2: Check addr + size - 1
        guest_addr_valid() is always true if
        HOST_LONG_BITS <= TARGET_VIRT_ADDR_SPACE_BITS

 include/exec/cpu_ldst.h | 4 ++++
 linux-user/qemu.h       | 4 +++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/exec/cpu_ldst.h b/include/exec/cpu_ldst.h
index a08b11bd2c07..06080d27ba15 100644
--- a/include/exec/cpu_ldst.h
+++ b/include/exec/cpu_ldst.h
@@ -62,7 +62,11 @@ typedef uint64_t abi_ptr;
 /* All direct uses of g2h and h2g need to go away for usermode softmmu.  */
 #define g2h(x) ((void *)((unsigned long)(abi_ptr)(x) + guest_base))
 
+#if HOST_LONG_BITS <= TARGET_VIRT_ADDR_SPACE_BITS
+#define guest_addr_valid(x) (1)
+#else
 #define guest_addr_valid(x) ((x) <= GUEST_ADDR_MAX)
+#endif
 #define h2g_valid(x) guest_addr_valid((unsigned long)(x) - guest_base)
 
 static inline int guest_range_valid(unsigned long start, unsigned long len)
diff --git a/linux-user/qemu.h b/linux-user/qemu.h
index fab287b7ec50..4258e4162d26 100644
--- a/linux-user/qemu.h
+++ b/linux-user/qemu.h
@@ -456,7 +456,9 @@ extern unsigned long guest_stack_size;
 
 static inline int access_ok(int type, abi_ulong addr, abi_ulong size)
 {
-    return page_check_range((target_ulong)addr, size,
+    return guest_addr_valid(addr) &&
+           (size == 0 || guest_addr_valid(addr + size - 1)) &&
+           page_check_range((target_ulong)addr, size,
                             (type == VERIFY_READ) ? PAGE_READ : (PAGE_READ | PAGE_WRITE)) == 0;
 }
 
-- 
2.21.0