| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.10 398/452] um: chan_user: Fix winch_tramp() return value | Date | Tue, 7 Jun 2022 19:04:15 +0200 |
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From: Johannes Berg <johannes.berg@intel.com>
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> --- arch/um/drivers/chan_user.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
--- a/arch/um/drivers/chan_user.c +++ b/arch/um/drivers/chan_user.c @@ -220,7 +220,7 @@ static int winch_tramp(int fd, struct tt 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 tt * 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 tt goto out_close; } - return err; + return pid; out_close: close(fds[1]);
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