Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=d36174bc2bce0372693a9cfbdef8b2689c9982cb
Commit: d36174bc2bce0372693a9cfbdef8b2689c9982cb
Parent: f374ada53bd1ca7c16d7607369fccc6769704956
Author: Oleg Nesterov <[EMAIL PROTECTED]>
AuthorDate: Fri Feb 8 04:19:18 2008 -0800
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Fri Feb 8 09:22:28 2008 -0800
uglify kill_pid_info() to fix kill() vs exec() race
kill_pid_info()->pid_task() could be the old leader of the execing process.
In that case it is possible that the leader will be released before we take
siglock. This means that kill_pid_info() (and thus sys_kill()) can return a
false -ESRCH.
Change the code to retry when lock_task_sighand() fails. The endless loop is
not possible, __exit_signal() both clears ->sighand and does detach_pid().
Signed-off-by: Oleg Nesterov <[EMAIL PROTECTED]>
Cc: "Eric W. Biederman" <[EMAIL PROTECTED]>
Cc: Davide Libenzi <[EMAIL PROTECTED]>
Cc: Pavel Emelyanov <[EMAIL PROTECTED]>
Cc: Roland McGrath <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
kernel/signal.c | 15 ++++++++++++---
1 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/kernel/signal.c b/kernel/signal.c
index 3d3adb9..b0b43a4 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1050,17 +1050,26 @@ int kill_pgrp_info(int sig, struct siginfo *info,
struct pid *pgrp)
int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
{
- int error;
+ int error = -ESRCH;
struct task_struct *p;
rcu_read_lock();
if (unlikely(sig_needs_tasklist(sig)))
read_lock(&tasklist_lock);
+retry:
p = pid_task(pid, PIDTYPE_PID);
- error = -ESRCH;
- if (p)
+ if (p) {
error = group_send_sig_info(sig, info, p);
+ if (unlikely(error == -ESRCH))
+ /*
+ * The task was unhashed in between, try again.
+ * If it is dead, pid_task() will return NULL,
+ * if we race with de_thread() it will find the
+ * new leader.
+ */
+ goto retry;
+ }
if (unlikely(sig_needs_tasklist(sig)))
read_unlock(&tasklist_lock);
-
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