Linux: Implements support for EFAULT with ppoll's timeout

Only need to handle the timeout structure, the rest is handled in the kernel itself.
FEX-Emu · Jan 25, 2024 · aca9e7a · aca9e7a
1 parent 18f1a93
commit aca9e7a
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Showing 3 changed files with 37 additions and 24 deletions.
diff --git a/Source/Tools/LinuxEmulation/LinuxSyscalls/x32/FD.cpp b/Source/Tools/LinuxEmulation/LinuxSyscalls/x32/FD.cpp
@@ -263,7 +263,12 @@ namespace FEX::HLE::x32 {
       struct timespec tp64{};
       struct timespec *timed_ptr{};
       if (timeout_ts) {
-        tp64 = *timeout_ts;
+        struct timespec32 timeout{};
+        if (FaultSafeMemcpy::CopyFromUser(&timeout, timeout_ts, sizeof(timeout)) == EFAULT) {
+          return -EFAULT;
+        }
+
+        tp64 = timeout;
         timed_ptr = &tp64;
       }
 
@@ -275,7 +280,13 @@ namespace FEX::HLE::x32 {
         sigsetsize);
 
       if (timeout_ts) {
-        *timeout_ts = tp64;
+        struct timespec32 timeout{};
+        timeout = tp64;
+
+        if (FaultSafeMemcpy::CopyToUser(timeout_ts, &timeout, sizeof(timeout)) == EFAULT) {
+          // Write to user memory failed, this can occur if the timeout is defined in read-only memory.
+          // This is okay to happen, kernel continues happily.
+        }
       }
 
       SYSCALL_ERRNO();

diff --git a/Source/Tools/LinuxEmulation/LinuxSyscalls/x32/Types.h b/Source/Tools/LinuxEmulation/LinuxSyscalls/x32/Types.h
@@ -127,7 +127,7 @@ timespec32 {
   int32_t tv_sec;
   int32_t tv_nsec;
 
-  timespec32() = delete;
+  timespec32() = default;
 
   operator timespec() const {
     timespec spec{};

diff --git a/unittests/FEXLinuxTests/tests/syscalls/syscalls_efault.cpp b/unittests/FEXLinuxTests/tests/syscalls/syscalls_efault.cpp
@@ -16,18 +16,18 @@ TEST_CASE("poll") {
 }
 
 TEST_CASE("ppoll") {
-  // ppoll can return EFAULT for arguements 1, 3, 4
+  // ppoll can return EFAULT for arguments 1, 3, 4
   struct pollfd *invalid_fds = reinterpret_cast<struct pollfd *>(mmap(nullptr, sysconf(_SC_PAGESIZE), PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
   struct timespec *invalid_timespec = reinterpret_cast<struct timespec*>(mmap(nullptr, sysconf(_SC_PAGESIZE), PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
   sigset_t *invalid_sigset = reinterpret_cast<sigset_t*>(mmap(nullptr, sysconf(_SC_PAGESIZE), PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
 
-  {
+  SECTION("invalid fds") {
     auto ret = ::syscall(SYS_ppoll, invalid_fds, 1, 0, nullptr, nullptr);
     REQUIRE(ret == -1);
     CHECK(errno == EFAULT);
   }
 
-  {
+  SECTION("invalid timespec") {
     struct pollfd valid_fds {
       .fd = STDOUT_FILENO,
       .events = 0,
@@ -38,7 +38,7 @@ TEST_CASE("ppoll") {
     CHECK(errno == EFAULT);
   }
 
-  {
+  SECTION("invalid sigset") {
     struct pollfd valid_fds {
       .fd = STDOUT_FILENO,
       .events = 0,
@@ -51,7 +51,7 @@ TEST_CASE("ppoll") {
     CHECK(errno == EFAULT);
   }
 
-  {
+  SECTION("valid configuration") {
     struct pollfd valid_fds {
       .fd = STDOUT_FILENO,
       .events = 0,
@@ -65,7 +65,7 @@ TEST_CASE("ppoll") {
     REQUIRE(ret == 0);
   }
 
-  {
+  SECTION("invalid timespec write-back") {
     struct pollfd valid_fds {
       .fd = STDOUT_FILENO,
       .events = 0,
@@ -85,26 +85,32 @@ TEST_CASE("ppoll") {
   }
 }
 
+struct timespec64 {
+  uint64_t tv_sec, tv_nsec;
+};
+
+static const timespec64 readonly_ts {
+  .tv_sec = 1,
+  .tv_nsec = 0,
+};
+
+
 TEST_CASE("ppoll_64") {
 #ifndef SYS_ppoll_time64
 #define SYS_ppoll_time64 SYS_ppoll
 #endif
-  struct timespec64 {
-    uint64_t tv_sec, tv_nsec;
-  };
-
   // ppoll can return EFAULT for arguements 1, 3, 4
   struct pollfd *invalid_fds = reinterpret_cast<struct pollfd *>(mmap(nullptr, sysconf(_SC_PAGESIZE), PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
   timespec64 *invalid_timespec = reinterpret_cast<timespec64*>(mmap(nullptr, sysconf(_SC_PAGESIZE), PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
   sigset_t *invalid_sigset = reinterpret_cast<sigset_t*>(mmap(nullptr, sysconf(_SC_PAGESIZE), PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
 
-  {
+  SECTION("invalid fds") {
     auto ret = ::syscall(SYS_ppoll_time64, invalid_fds, 1, 0, nullptr, nullptr);
     REQUIRE(ret == -1);
     CHECK(errno == EFAULT);
   }
 
-  {
+  SECTION("invalid timespec") {
     struct pollfd valid_fds {
       .fd = STDOUT_FILENO,
       .events = 0,
@@ -115,7 +121,7 @@ TEST_CASE("ppoll_64") {
     CHECK(errno == EFAULT);
   }
 
-  {
+  SECTION("invalid sigset") {
     struct pollfd valid_fds {
       .fd = STDOUT_FILENO,
       .events = 0,
@@ -128,7 +134,7 @@ TEST_CASE("ppoll_64") {
     CHECK(errno == EFAULT);
   }
 
-  {
+  SECTION("valid configuration") {
     struct pollfd valid_fds {
       .fd = STDOUT_FILENO,
       .events = 0,
@@ -142,22 +148,18 @@ TEST_CASE("ppoll_64") {
     REQUIRE(ret == 0);
   }
 
-  {
+  SECTION("invalid timespec write-back") {
     struct pollfd valid_fds {
       .fd = STDOUT_FILENO,
       .events = 0,
       .revents = 0,
     };
 
     // Kernel will read timespec, but it then can't write the result back.
-    mprotect(invalid_timespec, sysconf(_SC_PAGESIZE), PROT_READ | PROT_WRITE);
-    invalid_timespec->tv_sec = 1;
-    mprotect(invalid_timespec, sysconf(_SC_PAGESIZE), PROT_READ);
-
     sigset_t valid_sigset{};
     sigemptyset(&valid_sigset);
-    auto ret = ::syscall(SYS_ppoll_time64, &valid_fds, 1, invalid_timespec, &valid_sigset, sizeof(uint64_t));
+    auto ret = ::syscall(SYS_ppoll_time64, &valid_fds, 1, &readonly_ts, &valid_sigset, sizeof(uint64_t));
     REQUIRE(ret == 0);
-    CHECK(invalid_timespec->tv_sec == 1);
+    CHECK(readonly_ts.tv_sec == 1);
   }
 }