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authorOleg Nesterov <oleg@tv-sign.ru>2008-04-30 00:53:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-30 08:29:37 -0700
commit2e2ba22ea4fd4bb85f0fa37c521066db6775cbef (patch)
treeaada1523affbcbe1301decad43ad0875e1f680c4
parent53c30337f2c61aff6eecf2a446e839641172f9bd (diff)
signals: check_kill_permission: check session under tasklist_lock
This wasn't documented, but as Atsushi Tsuji pointed out check_kill_permission() needs tasklist_lock for task_session_nr(). I missed this fact when removed tasklist from the callers. Change check_kill_permission() to take tasklist_lock for the SIGCONT case. Re-order security checks so that we take tasklist_lock only if/when it is actually needed. This is a minimal fix for now, tasklist will be removed later. Also change the code to use task_session() instead of task_session_nr(). Also, remove the SIGCONT check from cap_task_kill(), it is bogus (and the whole function is bogus. Serge, Eric, why it is still alive?). Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Acked-by: Atsushi Tsuji <a-tsuji@bk.jp.nec.com> Cc: Roland McGrath <roland@redhat.com> Cc: Serge Hallyn <serue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/signal.c24
1 files changed, 19 insertions, 5 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index 251cc13720b..24be82c0aae 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -533,6 +533,7 @@ static int rm_from_queue(unsigned long mask, struct sigpending *s)
static int check_kill_permission(int sig, struct siginfo *info,
struct task_struct *t)
{
+ struct pid *sid;
int error;
if (!valid_signal(sig))
@@ -545,11 +546,24 @@ static int check_kill_permission(int sig, struct siginfo *info,
if (error)
return error;
- if (((sig != SIGCONT) || (task_session_nr(current) != task_session_nr(t)))
- && (current->euid ^ t->suid) && (current->euid ^ t->uid)
- && (current->uid ^ t->suid) && (current->uid ^ t->uid)
- && !capable(CAP_KILL))
- return -EPERM;
+ if ((current->euid ^ t->suid) && (current->euid ^ t->uid) &&
+ (current->uid ^ t->suid) && (current->uid ^ t->uid) &&
+ !capable(CAP_KILL)) {
+ switch (sig) {
+ case SIGCONT:
+ read_lock(&tasklist_lock);
+ sid = task_session(t);
+ read_unlock(&tasklist_lock);
+ /*
+ * We don't return the error if sid == NULL. The
+ * task was unhashed, the caller must notice this.
+ */
+ if (!sid || sid == task_session(current))
+ break;
+ default:
+ return -EPERM;
+ }
+ }
return security_task_kill(t, info, sig, 0);
}