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um: chan_user: Fix winch_tramp() return value

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commit 57ae0b67b747031bc41fb44643aa5344ab58607e upstream.

The previous fix here was only partially correct, it did
result in returning a proper error value in case of error,
but it also clobbered the pid that we need to return from
this function (not just zero for success).

As a result, it returned 0 here, but later this is treated
as a pid and used to kill the process, but since it's now
0 we kill(0, SIGKILL), which makes UML kill itself rather
than just the helper thread.

Fix that and make it more obvious by using a separate
variable for the pid.

Fixes: ccf1236ecac4 ("um: fix error return code in winch_tramp()")
Reported-and-tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johannes Berg 2022-05-20 19:45:36 +02:00 committed by Greg Kroah-Hartman
parent 873069e393
commit 7f8fd5dd43
1 changed files with 5 additions and 4 deletions
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9
arch/um/drivers/chan_user.c
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@ -220,7 +220,7 @@ static int winch_tramp(int fd, struct tty_port *port, int *fd_out,
unsigned long *stack_out)
{
struct winch_data data;
int fds[2], n, err;
int fds[2], n, err, pid;
char c;
err = os_pipe(fds, 1, 1);
@ -238,8 +238,9 @@ static int winch_tramp(int fd, struct tty_port *port, int *fd_out,
* problem with /dev/net/tun, which if held open by this
* thread, prevents the TUN/TAP device from being reused.
*/
err = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out);
if (err < 0) {
pid = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out);
if (pid < 0) {
err = pid;
printk(UM_KERN_ERR "fork of winch_thread failed - errno = %d\n",
-err);
goto out_close;
@ -263,7 +264,7 @@ static int winch_tramp(int fd, struct tty_port *port, int *fd_out,
goto out_close;
}
return err;
return pid;
out_close:
close(fds[1]);