[sanitizer-common][Darwin] Improve mach_vm_region_recurse error handling #158670
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Some sanitizers use mach_vm_region_recurse on macOS to find a sufficiently large gap to allocate shadow memory. Some sandboxes do not allow this. When we get KERN_DENIED, we suggest to the user that it may have been blocked by the sandbox. For error codes other than KERN_INVALID_ADDRESS and KERN_DENIED, we make sure to log a message and not use the address. rdar://145860383
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compiler-rt:asan
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@llvm/pr-subscribers-compiler-rt-sanitizer Author: Andrew Haberlandt (ndrewh) ChangesSome sanitizers use mach_vm_region_recurse on macOS to find a sufficiently large gap to allocate shadow memory. Some sandboxes do not allow this. When we get KERN_DENIED, we suggest to the user that it may have been blocked by the sandbox. For error codes other than KERN_INVALID_ADDRESS and KERN_DENIED, we make sure to log a message and not use the address. rdar://145860383 Full diff: https://github.com/llvm/llvm-project/pull/158670.diff 2 Files Affected:
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
index d4811ff4ed217..a3c0c18ec5760 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp
@@ -1265,17 +1265,34 @@ uptr FindAvailableMemoryRange(uptr size, uptr alignment, uptr left_padding,
kr = mach_vm_region_recurse(mach_task_self(), &address, &vmsize, &depth,
(vm_region_info_t)&vminfo, &count);
- // There are cases where going beyond the processes' max vm does
- // not return KERN_INVALID_ADDRESS so we check for going beyond that
- // max address as well.
- if (kr == KERN_INVALID_ADDRESS || address > max_vm_address) {
+ if (kr == KERN_SUCCESS) {
+ // There are cases where going beyond the processes' max vm does
+ // not return KERN_INVALID_ADDRESS so we check for going beyond that
+ // max address as well.
+ if (address > max_vm_address) {
+ address = max_vm_address;
+ kr = -1; // break after this iteration.
+ }
+
+ if (max_occupied_addr)
+ *max_occupied_addr = address + vmsize;
+ } else if (kr == KERN_INVALID_ADDRESS) {
// No more regions beyond "address", consider the gap at the end of VM.
address = max_vm_address;
- vmsize = 0;
- kr = -1; // break after this iteration.
+
+ // We will break after this iteration anyway since kr != KERN_SUCCESS
+ } else if (kr == KERN_DENIED) {
+ Report("ERROR: Unable to find a memory range for dynamic shadow.\n");
+ Report("HINT: Ensure mach_vm_region_recurse is allowed under sandbox.\n");
+ Die();
} else {
- if (max_occupied_addr) *max_occupied_addr = address + vmsize;
+ Report("WARNING: mach_vm_region_recurse returned unexpected code %d\n",
+ kr);
+ DCHECK(false && "mach_vm_region_recurse returned unexpected code");
+ break; // address is not valid unless KERN_SUCCESS, therefore we must not
+ // use it.
}
+
if (free_begin != address) {
// We found a free region [free_begin..address-1].
uptr gap_start = RoundUpTo((uptr)free_begin + left_padding, alignment);
diff --git a/compiler-rt/test/asan/TestCases/Darwin/sandbox-vm-region-recurse.cpp b/compiler-rt/test/asan/TestCases/Darwin/sandbox-vm-region-recurse.cpp
new file mode 100644
index 0000000000000..0044335cc1282
--- /dev/null
+++ b/compiler-rt/test/asan/TestCases/Darwin/sandbox-vm-region-recurse.cpp
@@ -0,0 +1,34 @@
+// Check that if mach_vm_region_recurse is disallowed by sandbox, we report a message saying so.
+
+// RUN: %clangxx_asan -O0 %s -o %t
+// RUN: not %run sandbox-exec -p '(version 1)(allow default)(deny syscall-mig (kernel-mig-routine mach_vm_region_recurse))' %t 2>&1 | FileCheck --check-prefix=CHECK-DENY %s
+// RUN: not %run %t 2>&1 | FileCheck --check-prefix=CHECK-ALLOW %s
+// RUN: %clangxx_asan -O3 %s -o %t
+// RUN: not %run sandbox-exec -p '(version 1)(allow default)(deny syscall-mig (kernel-mig-routine mach_vm_region_recurse))' %t 2>&1 | FileCheck --check-prefix=CHECK-DENY %s
+// RUN: not %run %t 2>&1 | FileCheck --check-prefix=CHECK-ALLOW %s
+
+// sandbox-exec isn't available on iOS
+// UNSUPPORTED: ios
+
+// x86_64 does not use ASAN_SHADOW_OFFSET_DYNAMIC
+// UNSUPPORTED: x86_64-darwin
+// UNSUPPORTED: x86_64h-darwin
+
+#include <stdlib.h>
+
+int main() {
+ char *x = (char *)malloc(10 * sizeof(char));
+ free(x);
+ return x[5];
+ // CHECK-ALLOW: {{.*ERROR: AddressSanitizer: heap-use-after-free on address}}
+ // CHECK-DENY-NOT: {{.*ERROR: AddressSanitizer: heap-use-after-free on address}}
+ // CHECK-ALLOW: {{READ of size 1 at 0x.* thread T0}}
+ // CHECK-ALLOW: {{ #0 0x.* in main}}
+ // CHECK-ALLOW: {{freed by thread T0 here:}}
+ // CHECK-ALLOW: {{ #0 0x.* in free}}
+ // CHECK-ALLOW: {{ #1 0x.* in main}}
+ // CHECK-ALLOW: {{previously allocated by thread T0 here:}}
+ // CHECK-ALLOW: {{ #0 0x.* in malloc}}
+ // CHECK-ALLOW: {{ #1 0x.* in main}}
+ // CHECK-DENY: {{.*HINT: Ensure mach_vm_region_recurse is allowed under sandbox}}
+}
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compiler-rt/test/asan/TestCases/Darwin/sandbox-vm-region-recurse.cpp
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| kr = -1; // break after this iteration. | ||
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| // We will break after this iteration anyway since kr != KERN_SUCCESS | ||
| } else if (kr == KERN_DENIED) { |
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I would move this part up, to follow the 'early return/exit/Die' principle, otherwise I find it a bit harder to read (else as applied to what condition(s)? Once KERN_DENIED handling is out of the way, the following happy path logic has less variables (i.e. there's one less } else if () {
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I knew I saw it somewhere but only found it now, in Dan's comments to your other PR:
https://llvm.org/docs/CodingStandards.html#use-early-exits-and-continue-to-simplify-code
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Let's see what @DanBlackwell thinks, but I sort of prefer it the way it is right now since all of the branches are kr == <something> (it's basically a switch: but we can't do that here easily because of the break...). IMO it would be worse to try to move both of the early exits above
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I agree this feels a little clunky, but the point about the else here being equivalent to the default case of a switch is why I think the current layout is fine. And there are enough comments here to understand why we're setting the different variables.
ndrewh
changed the title
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Yeah OK, let's go with it. This function actually returns early in the happy case, and continues until exhausting all possibilities when it fails, so handling positive case on top is actually in line with 'early returns' principle. |
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Some sanitizers use mach_vm_region_recurse on macOS to find a sufficiently large gap to allocate shadow memory. Some sandboxes do not allow this.
When we get KERN_DENIED, we suggest to the user that it may have been blocked by the sandbox.
For error codes other than KERN_INVALID_ADDRESS and KERN_DENIED, we make sure to log a message and not use the address.
rdar://160625998