[Qemu-devel] [PATCH v4 05/11] linux-user: fix mmap/munmap/mprotect/mremap/shmat

[Max Filippov <jcmvbkbc@gmail.com>]

In linux-user QEMU that runs for a target with TARGET_ABI_BITS bigger
than L1_MAP_ADDR_SPACE_BITS an assertion in page_set_flags fires when
mmap, munmap, mprotect, mremap or shmat is called for an address outside
the guest address space. mmap and mprotect should return ENOMEM in such
case.

Introduce macro guest_range_valid that verifies if address range is
within guest address space and does not wrap around. Use that macro in
mmap/munmap/mprotect/mremap/shmat for error checking.

Cc: qemu-stable@nongnu.org
Cc: Riku Voipio <riku.voipio@iki.fi>
Cc: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
Changes v3->v4:
- change GUEST_ADDR_MAX and h2g_valid definitions as suggested by Laurent
  Vivier.

Changes v2->v3:
- fix comparison in guest_valid: it must be 'less' to preserve the existing
  functionality, not 'less or equal'.
- fix guest_range_valid: it may not use guest_valid, because single range
  that occupies all of the guest address space is valid.

 include/exec/cpu-all.h  |  4 ++++
 include/exec/cpu_ldst.h | 14 ++++++++------
 linux-user/mmap.c       | 20 +++++++++++++++-----
 linux-user/syscall.c    |  3 +++
 4 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 0b141683f095..6304cfa7e171 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -159,8 +159,12 @@ extern unsigned long guest_base;
 extern int have_guest_base;
 extern unsigned long reserved_va;
 
+#if HOST_LONG_BITS <= TARGET_VIRT_ADDR_SPACE_BITS
+#define GUEST_ADDR_MAX (reserved_va ? reserved_va : ~0ul)
+#else
 #define GUEST_ADDR_MAX (reserved_va ? reserved_va : \
                                     (1ul << TARGET_VIRT_ADDR_SPACE_BITS) - 1)
+#endif
 #else
 
 #include "exec/hwaddr.h"
diff --git a/include/exec/cpu_ldst.h b/include/exec/cpu_ldst.h
index 191f2e962a3c..22f5df9c8a92 100644
--- a/include/exec/cpu_ldst.h
+++ b/include/exec/cpu_ldst.h
@@ -52,15 +52,17 @@
 #define g2h(x) ((void *)((unsigned long)(target_ulong)(x) + guest_base))
 
 #if HOST_LONG_BITS <= TARGET_VIRT_ADDR_SPACE_BITS
-#define h2g_valid(x) 1
+#define guest_valid(x) 1
 #else
-#define h2g_valid(x) ({ \
-    unsigned long __guest = (unsigned long)(x) - guest_base; \
-    (__guest < (1ul << TARGET_VIRT_ADDR_SPACE_BITS)) && \
-    (!reserved_va || (__guest < reserved_va)); \
-})
+#define guest_valid(x) ((x) < GUEST_ADDR_MAX)
 #endif
 
+#define h2g_valid(x) guest_valid((unsigned long)(x) - guest_base)
+
+#define guest_range_valid(start, len) \
+    ({unsigned long l = (len); \
+     l <= GUEST_ADDR_MAX && (start) <= GUEST_ADDR_MAX - l; })
+
 #define h2g_nocheck(x) ({ \
     unsigned long __ret = (unsigned long)(x) - guest_base; \
     (abi_ulong)__ret; \
diff --git a/linux-user/mmap.c b/linux-user/mmap.c
index 0fbfd6dff20d..df81f9b803b6 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -80,8 +80,9 @@ int target_mprotect(abi_ulong start, abi_ulong len, int prot)
         return -EINVAL;
     len = TARGET_PAGE_ALIGN(len);
     end = start + len;
-    if (end < start)
-        return -EINVAL;
+    if (!guest_range_valid(start, len)) {
+        return -ENOMEM;
+    }
     prot &= PROT_READ | PROT_WRITE | PROT_EXEC;
     if (len == 0)
         return 0;
@@ -481,8 +482,8 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
 	 * It can fail only on 64-bit host with 32-bit target.
 	 * On any other target/host host mmap() handles this error correctly.
 	 */
-        if ((unsigned long)start + len - 1 > (abi_ulong) -1) {
-            errno = EINVAL;
+        if (!guest_range_valid(start, len)) {
+            errno = ENOMEM;
             goto fail;
         }
 
@@ -622,8 +623,10 @@ int target_munmap(abi_ulong start, abi_ulong len)
     if (start & ~TARGET_PAGE_MASK)
         return -EINVAL;
     len = TARGET_PAGE_ALIGN(len);
-    if (len == 0)
+    if (len == 0 || !guest_range_valid(start, len)) {
         return -EINVAL;
+    }
+
     mmap_lock();
     end = start + len;
     real_start = start & qemu_host_page_mask;
@@ -678,6 +681,13 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
     int prot;
     void *host_addr;
 
+    if (!guest_range_valid(old_addr, old_size) ||
+        ((flags & MREMAP_FIXED) &&
+         !guest_range_valid(new_addr, new_size))) {
+        errno = ENOMEM;
+        return -1;
+    }
+
     mmap_lock();
 
     if (flags & MREMAP_FIXED) {
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index e24f43c4a259..79245e73784f 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -4900,6 +4900,9 @@ static inline abi_ulong do_shmat(CPUArchState *cpu_env,
             return -TARGET_EINVAL;
         }
     }
+    if (!guest_range_valid(shmaddr, shm_info.shm_segsz)) {
+        return -TARGET_EINVAL;
+    }
 
     mmap_lock();
 
-- 
2.11.0