As stated in the original commit for pidfd_send_signal() we don't allow to signal processes through O_PATH file descriptors since it is semantically equivalent to a write on the pidfd. We already correctly error out right now and return EBADF if an O_PATH fd is passed. This is because we use file->f_op to detect whether a pidfd is passed and O_PATH fds have their file->f_op set to empty_fops in do_dentry_open() and thus fail the test. Thus, there is no regression. It's just semantically correct to use fdget() and return an error right from there instead of taking a reference and returning an error later.
Signed-off-by: Christian Brauner <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: "Eric W. Biederman" <[email protected]> Cc: Kees Cook <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Jann Horn <[email protected]> Cc: David Howells <[email protected]> Cc: "Michael Kerrisk (man-pages)" <[email protected]> Cc: Andy Lutomirsky <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Aleksa Sarai <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Al Viro <[email protected]> --- /* changelog */ v1: patch not present v2: - Oleg Nesterov <[email protected]>: - split out from following patch since the s/fdget_raw()/fdget()/ replacement is a fix unrelated to the theme of the following patch --- kernel/signal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/signal.c b/kernel/signal.c index f98448cf2def..227ba170298e 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -3581,7 +3581,7 @@ SYSCALL_DEFINE4(pidfd_send_signal, int, pidfd, int, sig, if (flags) return -EINVAL; - f = fdget_raw(pidfd); + f = fdget(pidfd); if (!f.file) return -EBADF; -- 2.21.0
