Add info about ptrace permissions

Update our documentation with better info about ptrace - IPC users
should be aware of required permissions. Add proposed, one of the
solutions into our docs. Also, update our examples and tests to work
without global change of ptrace_scope.

Co-authored-by: [email protected]

Author: PatKamin

.github/workflows/reusable_basic.yml

@@ -145,9 +145,6 @@ jobs:
     - name: Install libhwloc
       run: .github/scripts/install_hwloc.sh
 
-    - name: Set ptrace value for IPC test
-      run: sudo bash -c "echo 0 > /proc/sys/kernel/yama/ptrace_scope"
-
     - name: Get UMF version
       run: |
         VERSION=$(git describe --tags --abbrev=0 | grep -oP '\d+\.\d+\.\d+')

.github/workflows/reusable_fast.yml

@@ -88,10 +88,6 @@ jobs:
         sudo apt-get install -y cmake libnuma-dev libtbb-dev
         .github/scripts/install_hwloc.sh # install hwloc-2.3.0 instead of hwloc-2.1.0 present in the OS package
 
-    - name: Set ptrace value for IPC test (on Linux only)
-      if: ${{ matrix.os == 'ubuntu-latest' || matrix.os == 'ubuntu-20.04' }}
-      run: sudo bash -c "echo 0 > /proc/sys/kernel/yama/ptrace_scope"
-
     - name: Configure CMake
       if: matrix.simple_cmake == 'OFF'
       run: >

.github/workflows/reusable_proxy_lib.yml

@@ -34,9 +34,6 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y cmake libhwloc-dev libtbb-dev lcov
 
-      - name: Set ptrace value for IPC test
-        run: sudo bash -c "echo 0 > /proc/sys/kernel/yama/ptrace_scope"
-
       - name: Configure build
         run: >
           cmake

.github/workflows/reusable_sanitizers.yml

@@ -40,10 +40,6 @@ jobs:
         sudo apt-get update
         sudo apt-get install -y intel-oneapi-ippcp-devel intel-oneapi-ipp-devel intel-oneapi-common-oneapi-vars intel-oneapi-compiler-dpcpp-cpp
 
-
-    - name: Set ptrace value for IPC test
-      run: sudo bash -c "echo 0 > /proc/sys/kernel/yama/ptrace_scope"
-
     - name: Configure build
       run: >
         ${{ matrix.compiler.cxx == 'icpx' && '. /opt/intel/oneapi/setvars.sh &&' || ''}} 

README.md

@@ -159,15 +159,7 @@ OS memory provider supports two types of memory mappings (set by the `visibility
 IPC API requires the `UMF_MEM_MAP_SHARED` memory `visibility` mode
 (`UMF_RESULT_ERROR_INVALID_ARGUMENT` is returned otherwise).
 
-IPC API uses the file descriptor duplication. It requires using `pidfd_getfd(2)` to obtain
-a duplicate of another process's file descriptor (`pidfd_getfd(2)` is supported since Linux 5.6).
-Permission to duplicate another process's file descriptor is governed by a ptrace access mode
-`PTRACE_MODE_ATTACH_REALCREDS` check (see `ptrace(2)`) that can be changed using
-the `/proc/sys/kernel/yama/ptrace_scope` interface in the following way:
-
-```sh
-sudo bash -c "echo 0 > /proc/sys/kernel/yama/ptrace_scope"
-```
+IPC API uses file descriptor duplication, which requires the `pidfd_getfd(2)` system call to obtain a duplicate of another process's file descriptor. This system call is supported since Linux 5.6. Permission to duplicate another process's file descriptor is governed by the `PTRACE_MODE_ATTACH_REALCREDS` check (see `ptrace(2)`). To allow file descriptor duplication in a binary that opens IPC handle, you can call `prctl(PR_SET_PTRACER, getppid())` in the producer binary that gets the IPC handle.
 
 There are available two mechanisms for the shared memory mapping:
 
@@ -194,15 +186,7 @@ Packages required for tests (Linux-only yet):
 
 A memory provider that provides memory from L0 device.
 
-IPC API uses the file descriptor duplication. It requires using `pidfd_getfd(2)` to obtain
-a duplicate of another process's file descriptor (`pidfd_getfd(2)` is supported since Linux 5.6).
-Permission to duplicate another process's file descriptor is governed by a ptrace access mode
-`PTRACE_MODE_ATTACH_REALCREDS` check (see `ptrace(2)`) that can be changed using
-the `/proc/sys/kernel/yama/ptrace_scope` interface in the following way:
-
-```sh
-sudo bash -c "echo 0 > /proc/sys/kernel/yama/ptrace_scope"
-```
+IPC API uses file descriptor duplication, which requires the `pidfd_getfd(2)` system call to obtain a duplicate of another process's file descriptor. This system call is supported since Linux 5.6. Permission to duplicate another process's file descriptor is governed by the `PTRACE_MODE_ATTACH_REALCREDS` check (see `ptrace(2)`). To allow file descriptor duplication in a binary that opens IPC handle, you can call `prctl(PR_SET_PTRACER, getppid())` in the producer binary that gets the IPC handle.
 
 ##### Requirements
 
@@ -359,7 +343,7 @@ The memory used by the proxy memory allocator is mmap'ed:
 1) with the `MAP_PRIVATE` flag by default or
 2) with the `MAP_SHARED` flag if the `UMF_PROXY` environment variable contains one of two following strings: `page.disposition=shared-shm` or `page.disposition=shared-fd`. These two options differ in a mechanism used during IPC:
    - `page.disposition=shared-shm` - IPC uses the named shared memory. An SHM name is generated using the `umf_proxy_lib_shm_pid_$PID` pattern, where `$PID` is the PID of the process. It creates the `/dev/shm/umf_proxy_lib_shm_pid_$PID` file.
-   - `page.disposition=shared-fd` - IPC uses the file descriptor duplication. It requires using `pidfd_getfd(2)` to obtain a duplicate of another process's file descriptor. Permission to duplicate another process's file descriptor is governed by a ptrace access mode `PTRACE_MODE_ATTACH_REALCREDS` check (see `ptrace(2)`) that can be changed using the `/proc/sys/kernel/yama/ptrace_scope` interface. `pidfd_getfd(2)` is supported since Linux 5.6.
+   - `page.disposition=shared-fd` - IPC API uses file descriptor duplication, which requires the `pidfd_getfd(2)` system call to obtain a duplicate of another process's file descriptor. This system call is supported since Linux 5.6. Permission to duplicate another process's file descriptor is governed by the `PTRACE_MODE_ATTACH_REALCREDS` check (see `ptrace(2)`). To allow file descriptor duplication in a binary that opens IPC handle, you can call `prctl(PR_SET_PTRACER, getppid())` in the producer binary that gets the IPC handle.
 
 **Size threshold**
 

examples/ipc_ipcapi/ipc_ipcapi_anon_fd.sh

@@ -1,5 +1,5 @@
 #
-# Copyright (C) 2024 Intel Corporation
+# Copyright (C) 2024-2025 Intel Corporation
 #
 # Under the Apache License v2.0 with LLVM Exceptions. See LICENSE.TXT.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -16,16 +16,8 @@ PORT=$(( 1024 + ( $$ % ( 65535 - 1024 ))))
 # to obtain a duplicate of another process's file descriptor.
 # Permission to duplicate another process's file descriptor
 # is governed by a ptrace access mode PTRACE_MODE_ATTACH_REALCREDS check (see ptrace(2))
-# that can be changed using the /proc/sys/kernel/yama/ptrace_scope interface.
-PTRACE_SCOPE_FILE="/proc/sys/kernel/yama/ptrace_scope"
-VAL=0
-if [ -f $PTRACE_SCOPE_FILE ]; then
-	PTRACE_SCOPE_VAL=$(cat $PTRACE_SCOPE_FILE)
-	if [ $PTRACE_SCOPE_VAL -ne $VAL ]; then
-		echo "SKIP: ptrace_scope is not set to 0 (classic ptrace permissions) - skipping the test"
-		exit 125 # skip code defined in CMakeLists.txt
-	fi
-fi
+# In the producer binary used in this example prctl(PR_SET_PTRACER, getppid()) is used
+# to allow consumer to duplicate file descriptor of producer.
 
 UMF_LOG_VAL="level:debug;flush:debug;output:stderr;pid:yes"
 

examples/ipc_ipcapi/ipc_ipcapi_producer.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2024 Intel Corporation
+ * Copyright (C) 2024-2025 Intel Corporation
  *
  * Under the Apache License v2.0 with LLVM Exceptions. See LICENSE.TXT.
  * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -9,6 +9,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/prctl.h>
 #include <sys/socket.h>
 #include <unistd.h>
 
@@ -69,6 +70,21 @@ int main(int argc, char *argv[]) {
 
     int port = atoi(argv[1]);
 
+    // The prctl() function with PR_SET_PTRACER is used here to allow parent process and its children
+    // to ptrace the current process. This is necessary because UMF's memory providers on Linux (except CUDA)
+    // use the pidfd_getfd(2) system call to duplicate another process's file descriptor, which is
+    // governed by ptrace permissions. By default on Ubuntu /proc/sys/kernel/yama/ptrace_scope is
+    // set to 1 ("restricted ptrace"), which prevents pidfd_getfd from working unless ptrace_scope
+    // is set to 0.
+    // To overcome this limitation without requiring users to change the ptrace_scope
+    // setting (which requires root privileges), we use prctl() to allow the consumer process
+    // to copy producer's file descriptor, even when ptrace_scope is set to 1.
+    ret = prctl(PR_SET_PTRACER, getppid());
+    if (ret == -1) {
+        perror("PR_SET_PTRACER may be not supported. prctl() call failed");
+        goto err_end;
+    }
+
     umf_memory_provider_handle_t OS_memory_provider = NULL;
     umf_os_memory_provider_params_handle_t os_params = NULL;
     enum umf_result_t umf_result;
@@ -259,6 +275,7 @@ int main(int argc, char *argv[]) {
 err_destroy_OS_params:
     umfOsMemoryProviderParamsDestroy(os_params);
 
+err_end:
     if (ret == 0) {
         fprintf(stderr, "[producer] Shutting down (status OK) ...\n");
     } else if (ret == 1) {

scripts/qemu/run-tests.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
-# Copyright (C) 2024 Intel Corporation
+# Copyright (C) 2024-2025 Intel Corporation
 # Under the Apache License v2.0 with LLVM Exceptions. See LICENSE.TXT.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
@@ -23,8 +23,6 @@ UMF_DIR=$(pwd)
 # Drop caches, restores free memory on NUMA nodes
 echo password | sudo sync;
 echo password | sudo sh -c "/usr/bin/echo 3 > /proc/sys/vm/drop_caches"
-# Set ptrace value for IPC test
-echo password | sudo bash -c "echo 0 > /proc/sys/kernel/yama/ptrace_scope"
 
 numactl -H
 

src/utils/utils_posix_common.c

@@ -1,6 +1,6 @@
 /*
  *
- * Copyright (C) 2024 Intel Corporation
+ * Copyright (C) 2024-2025 Intel Corporation
  *
  * Under the Apache License v2.0 with LLVM Exceptions. See LICENSE.TXT.
  * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -91,9 +91,8 @@ umf_result_t utils_duplicate_fd(int pid, int fd_in, int *fd_out) {
     return UMF_RESULT_ERROR_NOT_SUPPORTED;
 #else
     // pidfd_getfd(2) is used to obtain a duplicate of another process's file descriptor.
-    // Permission to duplicate another process's file descriptor
-    // is governed by a ptrace access mode PTRACE_MODE_ATTACH_REALCREDS check (see ptrace(2))
-    // that can be changed using the /proc/sys/kernel/yama/ptrace_scope interface.
+    // Calling prctl(PR_SET_PTRACER, getppid()) in a producer binary that creates IPC handle
+    // allows file descriptor duplication for parent process and its children.
     // pidfd_getfd(2) is supported since Linux 5.6
     // pidfd_open(2) is supported since Linux 5.3
     errno = 0;

test/common/ipc_common.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2024 Intel Corporation
+ * Copyright (C) 2024-2025 Intel Corporation
  *
  * Under the Apache License v2.0 with LLVM Exceptions. See LICENSE.TXT.
  * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
@@ -9,6 +9,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/prctl.h>
 #include <sys/socket.h>
 #include <unistd.h>
 
@@ -336,6 +337,12 @@ int run_producer(int port, umf_memory_pool_ops_t *pool_ops, void *pool_params,
     int producer_socket = -1;
     char consumer_message[MSG_SIZE];
 
+    ret = prctl(PR_SET_PTRACER, getppid());
+    if (ret == -1) {
+        perror("PR_SET_PTRACER may be not supported. prctl() call failed");
+        goto err_end;
+    }
+
     // create OS memory provider
     umf_result =
         umfMemoryProviderCreate(provider_ops, provider_params, &provider);
@@ -528,6 +535,7 @@ int run_producer(int port, umf_memory_pool_ops_t *pool_ops, void *pool_params,
 err_umfMemoryProviderDestroy:
     umfMemoryProviderDestroy(provider);
 
+err_end:
     if (ret == 0) {
         fprintf(stderr, "[producer] Shutting down (status OK) ...\n");
     } else if (ret == 1) {