Update the kill(2) and killpg(2) man pages to the modern permission

checks. Also indicate killpg(2) is POSIX compliant.

Reviewed by:	jilles
Reviewed by:	wblock
Approved by:	cperciva
MFC after:	3 days

2 files changed, 20 insertions, 16 deletions

diff --git a/lib/libc/compat-43/killpg.2 b/lib/libc/compat-43/killpg.2
index b23b773..a1d52a4 100644
--- a/lib/libc/compat-43/killpg.2
+++ b/lib/libc/compat-43/killpg.2
@@ -58,11 +58,9 @@ is 0,
 .Fn killpg
 sends the signal to the sending process's process group.
 .Pp
-The sending process and members of the process group must
-have the same effective user ID, or
-the sender must be the super-user.
-As a single special case the continue signal SIGCONT may be sent
-to any process with the same session ID as the caller.
+The sending process must be able to
+.Fn kill
+at least one process in the receiving process group.
 .Sh RETURN VALUES
 .Rv -std killpg
 .Sh ERRORS
@@ -80,9 +78,8 @@ is not a valid signal number.
 No process can be found in the process group specified by
 .Fa pgrp .
 .It Bq Er EPERM
-The sending process is not the super-user and one or more
-of the target processes has an effective user ID different from that
-of the sending process.
+.Fn kill
+returns EPERM for all processes in the process group.
 .El
 .Sh SEE ALSO
 .Xr getpgrp 2 ,
diff --git a/lib/libc/sys/kill.2 b/lib/libc/sys/kill.2
index 0389559..98c3050 100644
--- a/lib/libc/sys/kill.2
+++ b/lib/libc/sys/kill.2
@@ -64,11 +64,19 @@ This can be used to check the validity of
 For a process to have permission to send a signal to a process designated
 by
 .Fa pid ,
-the real or effective user ID of the receiving process must match
-that of the sending process or the user must have appropriate privileges
-(such as given by a set-user-ID program or the user is the super-user).
+the user must be the super-user, or
+the real or saved user ID of the receiving process must match
+the real or effective user ID of the sending process.
 A single exception is the signal SIGCONT, which may always be sent
-to any process with the same session ID as the caller.
+to any process with the same session ID as the sender.
+In addition, if the
+.Va security.bsd.conservative_signals
+.Xr sysctl
+is set to 1, the user is not a super-user, and
+the receiver is set-uid, then
+only job control and terminal control signals may
+be sent (in particular, only SIGKILL, SIGINT, SIGTERM, SIGALRM,
+SIGSTOP, SIGTTIN, SIGTTOU, SIGTSTP, SIGHUP, SIGUSR1, SIGUSR2).
 .Bl -tag -width Ds
 .It \&If Fa pid No \&is greater than zero :
 The
@@ -124,10 +132,9 @@ is not a valid signal number.
 No process or process group can be found corresponding to that specified by
 .Fa pid .
 .It Bq Er EPERM
-The sending process is not the super-user and its effective
-user id does not match the effective user-id of the receiving process.
-When signaling a process group, this error is returned if any members
-of the group could not be signaled.
+The sending process does not have permission to send
+.Va sig
+to the receiving process.
 .El
 .Sh SEE ALSO
 .Xr getpgrp 2 ,