tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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fix bogus reporting of signals by audit

Async signals should not be reported as sent by current in audit log. As
it is, we call audit_signal_info() too early in check_kill_permission().
Note that check_kill_permission() has that test already - it needs to know
if it should apply current-based permission checks. So the solution is to
move the call of audit_signal_info() between those.

Bogosity in question is easily reproduced - add a rule watching for e.g.
kill(2) from specific process (so that audit_signal_info() would not
short-circuit to nothing), say load_policy, watch the bogus OBJ_PID entry
in audit logs claiming that write(2) on selinuxfs file issued by
load_policy(8) had somehow managed to send a signal to syslogd...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Steve Grubb <sgrubb@redhat.com>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

authored by

Al Viro and committed by
Linus Torvalds 291041e9 7a5c5d57

+11 -11
+11 -11
kernel/signal.c
··· 531 531 if (!valid_signal(sig)) 532 532 return error; 533 533 534 - error = audit_signal_info(sig, t); /* Let audit system see the signal */ 535 - if (error) 534 + if (info == SEND_SIG_NOINFO || (!is_si_special(info) && SI_FROMUSER(info))) { 535 + error = audit_signal_info(sig, t); /* Let audit system see the signal */ 536 + if (error) 537 + return error; 538 + error = -EPERM; 539 + if (((sig != SIGCONT) || 540 + (process_session(current) != process_session(t))) 541 + && (current->euid ^ t->suid) && (current->euid ^ t->uid) 542 + && (current->uid ^ t->suid) && (current->uid ^ t->uid) 543 + && !capable(CAP_KILL)) 536 544 return error; 537 - 538 - error = -EPERM; 539 - if ((info == SEND_SIG_NOINFO || (!is_si_special(info) && SI_FROMUSER(info))) 540 - && ((sig != SIGCONT) || 541 - (process_session(current) != process_session(t))) 542 - && (current->euid ^ t->suid) && (current->euid ^ t->uid) 543 - && (current->uid ^ t->suid) && (current->uid ^ t->uid) 544 - && !capable(CAP_KILL)) 545 - return error; 545 + } 546 546 547 547 return security_task_kill(t, info, sig, 0); 548 548 }