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win: almost fix race detecting ESRCH in uv_kill (#4341)

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It might happen that only using `WaitForSingleObject()` with timeout 0
could return WAIT_TIMEOUT as the process might not have been signaled
yet. To improve things, first use `GetExitCodeProcess()` and check
that `status` is not `STILL_ACTIVE`. Then, to cover for the case that the exit
code was actually `STILL_ACTIVE` use `WaitForSingleObject()`. This could
still be prone to the race condition but only for that case.
This commit is contained in:
Santiago Gimeno 2024-03-05 21:20:50 +01:00 committed by GitHub
parent 625d3d275a
commit ff9587991f
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GPG Key ID: B5690EEEBB952194
1 changed files with 30 additions and 4 deletions
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34
src/win/process.c
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@ -1308,16 +1308,34 @@ static int uv__kill(HANDLE process_handle, int signum) {
/* Unconditionally terminate the process. On Windows, killed processes
* normally return 1. */
int err;
DWORD status;
if (TerminateProcess(process_handle, 1))
return 0;
/* If the process already exited before TerminateProcess was called,.
/* If the process already exited before TerminateProcess was called,
* TerminateProcess will fail with ERROR_ACCESS_DENIED. */
err = GetLastError();
if (err == ERROR_ACCESS_DENIED &&
WaitForSingleObject(process_handle, 0) == WAIT_OBJECT_0) {
return UV_ESRCH;
if (err == ERROR_ACCESS_DENIED) {
/* First check using GetExitCodeProcess() with status different from
* STILL_ACTIVE (259). This check can be set incorrectly by the process,
* though that is uncommon. */
if (GetExitCodeProcess(process_handle, &status) &&
status != STILL_ACTIVE) {
return UV_ESRCH;
}
/* But the process could have exited with code == STILL_ACTIVE, use then
* WaitForSingleObject with timeout zero. This is prone to a race
* condition as it could return WAIT_TIMEOUT because the handle might
* not have been signaled yet.That would result in returning the wrong
* error code here (UV_EACCES instead of UV_ESRCH), but we cannot fix
* the kernel synchronization issue that TerminateProcess is
* inconsistent with WaitForSingleObject with just the APIs available to
* us in user space. */
if (WaitForSingleObject(process_handle, 0) == WAIT_OBJECT_0) {
return UV_ESRCH;
}
}
return uv_translate_sys_error(err);
@ -1325,6 +1343,14 @@ static int uv__kill(HANDLE process_handle, int signum) {
case 0: {
/* Health check: is the process still alive? */
DWORD status;
if (!GetExitCodeProcess(process_handle, &status))
return uv_translate_sys_error(GetLastError());
if (status != STILL_ACTIVE)
return UV_ESRCH;
switch (WaitForSingleObject(process_handle, 0)) {
case WAIT_OBJECT_0:
return UV_ESRCH;