[libc] Unpoison epoll structs

[michaelrj-google]

The epoll wait functions return structs via pointer, but those structs
need to be unpoisoned before return. This patch adds that unpoisoning.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Michael Jones (michaelrj-google)

Changes

The epoll wait functions return structs via pointer, but those structs
need to be unpoisoned before return. This patch adds that unpoisoning.

---

Full diff: https://github.com/llvm/llvm-project/pull/94536.diff

5 Files Affected:

• (modified) libc/src/sys/epoll/linux/CMakeLists.txt (+3)
• (modified) libc/src/sys/epoll/linux/epoll_pwait.cpp (+3)
• (modified) libc/src/sys/epoll/linux/epoll_pwait2.cpp (+3)
• (modified) libc/src/sys/epoll/linux/epoll_wait.cpp (+3)
• (modified) utils/bazel/llvm-project-overlay/libc/BUILD.bazel (+5-2)

diff --git a/libc/src/sys/epoll/linux/CMakeLists.txt b/libc/src/sys/epoll/linux/CMakeLists.txt
index 4e661b262b85b..5ba89bd1af603 100644
--- a/libc/src/sys/epoll/linux/CMakeLists.txt
+++ b/libc/src/sys/epoll/linux/CMakeLists.txt
@@ -48,6 +48,7 @@ add_entrypoint_object(
     libc.hdr.types.struct_timespec
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
+    libc.src.__support.macros.sanitizer
     libc.src.errno.errno
 )
 
@@ -65,6 +66,7 @@ add_entrypoint_object(
     libc.hdr.signal_macros
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
+    libc.src.__support.macros.sanitizer
     libc.src.errno.errno
 )
 
@@ -82,5 +84,6 @@ add_entrypoint_object(
     libc.hdr.signal_macros
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
+    libc.src.__support.macros.sanitizer
     libc.src.errno.errno
 )
diff --git a/libc/src/sys/epoll/linux/epoll_pwait.cpp b/libc/src/sys/epoll/linux/epoll_pwait.cpp
index 8f498d18d547d..24b66f0721b30 100644
--- a/libc/src/sys/epoll/linux/epoll_pwait.cpp
+++ b/libc/src/sys/epoll/linux/epoll_pwait.cpp
@@ -13,6 +13,7 @@
 #include "hdr/types/struct_epoll_event.h"
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
+#include "src/__support/macros/sanitizer.h"
 #include "src/errno/libc_errno.h"
 
 #include <sys/syscall.h> // For syscall numbers.
@@ -33,6 +34,8 @@ LLVM_LIBC_FUNCTION(int, epoll_pwait,
     return -1;
   }
 
+  MSAN_UNPOISON(events, ret * sizeof(struct epoll_event));
+
   return ret;
 }
 
diff --git a/libc/src/sys/epoll/linux/epoll_pwait2.cpp b/libc/src/sys/epoll/linux/epoll_pwait2.cpp
index bd33cb6325cea..e13423a085a59 100644
--- a/libc/src/sys/epoll/linux/epoll_pwait2.cpp
+++ b/libc/src/sys/epoll/linux/epoll_pwait2.cpp
@@ -14,6 +14,7 @@
 #include "hdr/types/struct_timespec.h"
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
+#include "src/__support/macros/sanitizer.h"
 #include "src/errno/libc_errno.h"
 
 #include <sys/syscall.h> // For syscall numbers.
@@ -35,6 +36,8 @@ LLVM_LIBC_FUNCTION(int, epoll_pwait2,
     return -1;
   }
 
+  MSAN_UNPOISON(events, ret * sizeof(struct epoll_event));
+
   return ret;
 }
 
diff --git a/libc/src/sys/epoll/linux/epoll_wait.cpp b/libc/src/sys/epoll/linux/epoll_wait.cpp
index 95238d872d52f..3ce4a92e79695 100644
--- a/libc/src/sys/epoll/linux/epoll_wait.cpp
+++ b/libc/src/sys/epoll/linux/epoll_wait.cpp
@@ -13,6 +13,7 @@
 #include "hdr/types/struct_epoll_event.h"
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
+#include "src/__support/macros/sanitizer.h"
 #include "src/errno/libc_errno.h"
 
 #include <sys/syscall.h> // For syscall numbers.
@@ -39,6 +40,8 @@ LLVM_LIBC_FUNCTION(int, epoll_wait,
     return -1;
   }
 
+  MSAN_UNPOISON(events, ret * sizeof(struct epoll_event));
+
   return ret;
 }
 
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index f3809bd748140..96cc895559319 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -1111,7 +1111,7 @@ libc_support_library(
     ],
     defines = [
         "LIBC_COPT_TIMEOUT_ENSURE_MONOTONICITY",
-        "LIBC_COPT_RAW_MUTEX_DEFAULT_SPIN_COUNT"
+        "LIBC_COPT_RAW_MUTEX_DEFAULT_SPIN_COUNT",
     ],
     target_compatible_with = select({
         "@platforms//os:linux": [],
@@ -1119,9 +1119,9 @@ libc_support_library(
     }),
     deps = [
         ":__support_cpp_optional",
-        ":__support_time_linux",
         ":__support_threads_linux_futex_utils",
         ":__support_threads_sleep",
+        ":__support_time_linux",
         ":types_pid_t",
     ],
 )
@@ -3580,6 +3580,7 @@ libc_function(
     }),
     weak = True,
     deps = [
+        ":__support_macros_sanitizer",
         ":__support_osutil_syscall",
         ":errno",
         ":hdr_signal_macros",
@@ -3599,6 +3600,7 @@ libc_function(
     }),
     weak = True,
     deps = [
+        ":__support_macros_sanitizer",
         ":__support_osutil_syscall",
         ":errno",
         ":hdr_signal_macros",
@@ -3620,6 +3622,7 @@ libc_function(
 #     }),
 #     weak = True,
 #     deps = [
+#         ":__support_macros_sanitizer",
 #         ":__support_osutil_syscall",
 #         ":errno",
 #         ":hdr_signal_macros",

[alexfh]

Thanks for the quick fix!
LGTM