linux-user: fix mmap/munmap/mprotect/mremap/shmat

PATCH Superseded Max Filippov 2 participants 4 messages Mar 7, 2018

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Max Filippov

author

2018-03-07 06:37 UTC #0 lore raw

PATCH v5 5/11 linux-user: fix mmap/munmap/mprotect/mremap/shmat

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.

Change definition of GUEST_ADDR_MAX to always be the last valid guest address. Account for this change in open_self_maps.
Add macro guest_addr_valid that verifies if the guest address is valid. Add function 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 [email protected]

Cc Riku Voipio <[email protected]>

Cc Laurent Vivier <[email protected]>

Signed-off-by Max Filippov <[email protected]>

---
Changes v4->v5:
- change definition of GUEST_ADDR_MAX to always be the last valid guest address. Account for this change in guest_addr_valid and open_self_maps.
- turn guest_range_valid into a function.

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  |  6 +++++-
 include/exec/cpu_ldst.h | 19 ++++++++++---------
 linux-user/mmap.c       | 20 +++++++++++++++-----
 linux-user/syscall.c    |  5 ++++-
 4 files changed, 34 insertions(+), 16 deletions(-)

include/exec/cpu-all.h +5 -1

index 0b141683f095..f4fa94e9669d 100644
@@ -159,8 +159,12 @@ extern unsigned long guest_base;
 extern int have_guest_base;
 extern unsigned long reserved_va;
 
-#define GUEST_ADDR_MAX (reserved_va ? reserved_va : \
+#if HOST_LONG_BITS <= TARGET_VIRT_ADDR_SPACE_BITS
+#define GUEST_ADDR_MAX (~0ul)
+#else
+#define GUEST_ADDR_MAX (reserved_va ? reserved_va - 1 : \
                                     (1ul << TARGET_VIRT_ADDR_SPACE_BITS) - 1)
+#endif
 #else
 
 #include "exec/hwaddr.h"

include/exec/cpu_ldst.h +10 -9

index 191f2e962a3c..313664e9dae8 100644
@@ -51,15 +51,16 @@
 /* All direct uses of g2h and h2g need to go away for usermode softmmu.  */
 #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
-#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)); \
-})
-#endif
+#define guest_addr_valid(x) ((x) <= GUEST_ADDR_MAX)
+#define h2g_valid(x) guest_addr_valid((unsigned long)(x) - guest_base)
+
+static inline int guest_range_valid(unsigned long start, unsigned long len)
+{
+    if (len)
+        return guest_addr_valid(len - 1) && start <= GUEST_ADDR_MAX - len + 1;
+    else
+        return guest_addr_valid(start);
+}
 
 #define h2g_nocheck(x) ({ \
     unsigned long __ret = (unsigned long)(x) - guest_base; \

linux-user/mmap.c +15 -5

index 0fbfd6dff20d..df81f9b803b6 100644
@@ -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) {

linux-user/syscall.c +4 -1

index e24f43c4a259..809644742aff 100644
@@ -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();

@@ -7468,7 +7471,7 @@ static int open_self_maps(void *cpu_env, int fd)
         }
         if (h2g_valid(min)) {
             int flags = page_get_flags(h2g(min));
-            max = h2g_valid(max - 1) ? max : (uintptr_t)g2h(GUEST_ADDR_MAX);
+            max = h2g_valid(max - 1) ? max : (uintptr_t)g2h(GUEST_ADDR_MAX) + 1;
             if (page_check_range(h2g(min), max - min, flags) == -1) {
                 continue;
             }

Signature · 1 line

2.11.0

Laurent Vivier

2018-03-07 10:08 UTC #1 lore raw

Le 07/03/2018 à 07:36, Max Filippov a écrit :

Quoted 74 lines

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.
Change definition of GUEST_ADDR_MAX to always be the last valid guest address. Account for this change in open_self_maps.
Add macro guest_addr_valid that verifies if the guest address is valid. Add function 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 [email protected]
Cc Riku Voipio <[email protected]>
Cc Laurent Vivier <[email protected]>
Signed-off-by Max Filippov <[email protected]>
---
Changes v4->v5:
- change definition of GUEST_ADDR_MAX to always be the last valid guest address. Account for this change in guest_addr_valid and open_self_maps.
- turn guest_range_valid into a function.
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  |  6 +++++-
 include/exec/cpu_ldst.h | 19 ++++++++++---------
 linux-user/mmap.c       | 20 +++++++++++++++-----
 linux-user/syscall.c    |  5 ++++-
 4 files changed, 34 insertions(+), 16 deletions(-)
include/exec/cpu-all.h +5 -1
index 0b141683f095..f4fa94e9669d 100644
@@ -159,8 +159,12 @@ extern unsigned long guest_base;
 extern int have_guest_base;
 extern unsigned long reserved_va;
 
-#define GUEST_ADDR_MAX (reserved_va ? reserved_va : \
+#if HOST_LONG_BITS <= TARGET_VIRT_ADDR_SPACE_BITS
+#define GUEST_ADDR_MAX (~0ul)
+#else
+#define GUEST_ADDR_MAX (reserved_va ? reserved_va - 1 : \
                                     (1ul << TARGET_VIRT_ADDR_SPACE_BITS) - 1)
+#endif
 #else
 
 #include "exec/hwaddr.h"
include/exec/cpu_ldst.h +0 -9
index 191f2e962a3c..313664e9dae8 100644
@@ -51,15 +51,16 @@
 /* All direct uses of g2h and h2g need to go away for usermode softmmu.  */
 #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
-#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)); \
-})
-#endif

include/exec/cpu_ldst.h line 63

Quoted 10 lines

include/exec/cpu_ldst.h +10 -0

+#define guest_addr_valid(x) ((x) <= GUEST_ADDR_MAX)
+#define h2g_valid(x) guest_addr_valid((unsigned long)(x) - guest_base)
+
+static inline int guest_range_valid(unsigned long start, unsigned long len)
+{
+    if (len)
+        return guest_addr_valid(len - 1) && start <= GUEST_ADDR_MAX - len + 1;
+    else
+        return guest_addr_valid(start);
+}

I think we can consider len == 0 is invalid and use only:

  return start + (len - 1) <= GUEST_ADDR_MAX;

Thanks,
Laurent

Max Filippov

author

2018-03-07 17:46 UTC #2 lore raw

Quoted 11 lines · Laurent Vivier

include/exec/cpu_ldst.h line 63

Quoted 7 lines

include/exec/cpu_ldst.h +7 -0

+static inline int guest_range_valid(unsigned long start, unsigned long len)
+{
+    if (len)
+        return guest_addr_valid(len - 1) && start <= GUEST_ADDR_MAX - len + 1;
+    else
+        return guest_addr_valid(start);
+}

I think we can consider len == 0 is invalid and use only:

  return start + (len - 1) <= GUEST_ADDR_MAX;

start + len - 1 may wrap around, that's why I first validate len and then have len at the right side of the comparison. I.e. if we drop check for len == 0 I'd still write it as

  guest_addr_valid(len - 1) && start <= GUEST_ADDR_MAX - len + 1;

Signature · 2 lines

Thanks.
-- Max

Laurent Vivier

2018-03-07 20:14 UTC #3 lore raw

Le 07/03/2018 à 18:45, Max Filippov a écrit :

Quoted 11 lines · Laurent Vivier

Quoted 10 lines
include/exec/cpu_ldst.h line 63
Quoted 7 lines
include/exec/cpu_ldst.h +7 -0
+static inline int guest_range_valid(unsigned long start, unsigned long len)
+{
+    if (len)
+        return guest_addr_valid(len - 1) && start <= GUEST_ADDR_MAX - len + 1;
+    else
+        return guest_addr_valid(start);
+}
I think we can consider len == 0 is invalid and use only:

Quoted 8 lines

Quoted 1 line
  return start + (len - 1) <= GUEST_ADDR_MAX;
start + len - 1 may wrap around, that's why I first validate len and then have len at the right side of the comparison. I.e. if we drop check for len == 0 I'd still write it as
  guest_addr_valid(len - 1) && start <= GUEST_ADDR_MAX - len + 1;

Yes, you're right.

it would be clearer to write:

    len - 1 <= GUEST_ADDR_MAX && start <= GUEST_ADDR_MAX - len + 1;

but it's only cosmetic.

Thanks,
Laurent