The patch titled uglify kill_pid_info() to fix kill() vs exec() race has been removed from the -mm tree. Its filename was uglify-kill_pid_info-to-fix-kill-vs-exec-race.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: uglify kill_pid_info() to fix kill() vs exec() race From: Oleg Nesterov <oleg@xxxxxxxxxx> 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 <oleg@xxxxxxxxxx> Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> Cc: Davide Libenzi <davidel@xxxxxxxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxx> Cc: Roland McGrath <roland@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/signal.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff -puN kernel/signal.c~uglify-kill_pid_info-to-fix-kill-vs-exec-race kernel/signal.c --- a/kernel/signal.c~uglify-kill_pid_info-to-fix-kill-vs-exec-race +++ a/kernel/signal.c @@ -1050,17 +1050,26 @@ int kill_pgrp_info(int sig, struct sigin 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); _ Patches currently in -mm which might be from oleg@xxxxxxxxxx are origin.patch revert-proc-fix-the-threaded-proc-self.patch procfs-task-exe-symlink.patch procfs-task-exe-symlink-fix.patch - To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html