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uml: Fix unsafe pid reference to foreground process group 

Although the tty core maintains a pid reference for the foreground
process group, if the foreground process group is changed that
pid reference is dropped. Thus, the pid reference used for signalling
could become stale.

Safely obtain a pid reference to the foreground process group and
release the reference after signalling is complete.

cc: Jeff Dike <jdike@addtoit.com>
Acked-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2014-10-16 14:59:44 -04:00 committed by Greg Kroah-Hartman
parent bce65f1831
commit 8a8a55105d
1 changed files with 5 additions and 1 deletions
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6
arch/um/drivers/line.c
View File

@ -632,6 +632,7 @@ static irqreturn_t winch_interrupt(int irq, void *data)
int fd = winch->fd;
int err;
char c;
struct pid *pgrp;
if (fd != -1) {
err = generic_read(fd, &c, NULL);
@ -657,7 +658,10 @@ static irqreturn_t winch_interrupt(int irq, void *data)
if (line != NULL) {
chan_window_size(line, &tty->winsize.ws_row,
&tty->winsize.ws_col);
kill_pgrp(tty->pgrp, SIGWINCH, 1);
pgrp = tty_get_pgrp(tty);
if (pgrp)
kill_pgrp(pgrp, SIGWINCH, 1);
put_pid(pgrp);
}
tty_kref_put(tty);
}