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Cygwin: pipes: don't call NtQueryInformationFile on read side of pipes 

NtQueryInformationFile hangs if it's called on the read side handle of
a pipe while another thread or process is performing a blocking read.

Avoid select potentially hanging by calling NtQueryInformationFile
only on the write side of the pipe and using PeekNamedPipe otherwise.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2021-09-15 14:17:59 +02:00
parent f961a63ed6
commit 34b1447040
1 changed files with 8 additions and 0 deletions
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8
winsup/cygwin/select.cc
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@ -587,6 +587,14 @@ no_verify (select_record *, fd_set *, fd_set *, fd_set *)
static int static int
pipe_data_available (int fd, fhandler_base *fh, HANDLE h, bool writing) pipe_data_available (int fd, fhandler_base *fh, HANDLE h, bool writing)
{ {
if (fh->get_device () == FH_PIPER)
{
DWORD nbytes_in_pipe;
if (!writing && PeekNamedPipe (h, NULL, 0, NULL, &nbytes_in_pipe, NULL))
return nbytes_in_pipe > 0;
return -1;
}
IO_STATUS_BLOCK iosb = {{0}, 0}; IO_STATUS_BLOCK iosb = {{0}, 0};
FILE_PIPE_LOCAL_INFORMATION fpli = {0}; FILE_PIPE_LOCAL_INFORMATION fpli = {0};
NTSTATUS status; NTSTATUS status;