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* PATCH: bug fix: infinite loop in sysread
@ 2020-02-05 14:19 Roman Perepelitsa
  2020-02-05 20:55 ` Bart Schaefer
  2020-02-06 19:52 ` dana
  0 siblings, 2 replies; 7+ messages in thread
From: Roman Perepelitsa @ 2020-02-05 14:19 UTC (permalink / raw)
  To: Zsh hackers list

[-- Attachment #1: Type: text/plain, Size: 915 bytes --]

The attached patch fixes a bug in sysread from zsh/system. The bug
triggers in the following case:

1. zsh has been compiled with HAVE_SELECT and without HAVE_POLL
2. sysread is called with timeout (-t)
3. the input file descriptor is valid but there is no data to read
4. errno happens to be EINTR prior to the call to sysread

This results in an infinite loop in sysread:

  while ((ret = select(infd+1, (SELECT_ARG_2_T) &fds,
                       NULL, NULL,&select_tv)) < 1) {
      if (errno != EINTR || errflag || retflag || breaks || contflag)
          break;
  }

Here select() keeps returning 0, indicating timeout. This is not an
error, so errno doesn't get set. If it was EINTR prior to the call,
it stays EINTR, and the loop keeps spinning.

The fix is to replace `< 1` with `< 0` in the loop condition.

On GitHub:
https://github.com/zsh-users/zsh/compare/master...romkatv:fix-sysread-tmout

Roman.

[-- Attachment #2: fix-sysread-tmout.patch.txt --]
[-- Type: text/plain, Size: 456 bytes --]

diff --git a/Src/Modules/system.c b/Src/Modules/system.c
index 50de59cf9..fb3d80773 100644
--- a/Src/Modules/system.c
+++ b/Src/Modules/system.c
@@ -174,7 +174,7 @@ bin_sysread(char *nam, char **args, Options ops, UNUSED(int func))
 	}
 
 	while ((ret = select(infd+1, (SELECT_ARG_2_T) &fds,
-			     NULL, NULL,&select_tv)) < 1) {
+			     NULL, NULL,&select_tv)) < 0) {
 	    if (errno != EINTR || errflag || retflag || breaks || contflag)
 		break;
 	}

^ permalink raw reply	[flat|nested] 7+ messages in thread

end of thread, other threads:[~2020-02-07 16:50 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-02-05 14:19 PATCH: bug fix: infinite loop in sysread Roman Perepelitsa
2020-02-05 20:55 ` Bart Schaefer
2020-02-05 21:04   ` Roman Perepelitsa
2020-02-06 19:52 ` dana
2020-02-06 20:01   ` Peter Stephenson
2020-02-07 11:26   ` Roman Perepelitsa
2020-02-07 16:49     ` dana

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