From 1dd768c0815334d2319d6377f0750ace075b6142 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 30 Apr 2008 00:54:28 -0700 Subject: [PATCH] pids: sys_getsid: fix unsafe *pid usage, fix possible 0 instead of -ESRCH 1. sys_getsid() needs rcu_read_lock() to derive the session _nr, even if the task is current, otherwise we can race with another thread which does sys_setsid(). 2. The task can exit between find_task_by_vpid() and task_session_vnr(), in that unlikely case sys_getsid() returns 0 instead of -ESRCH. Signed-off-by: Oleg Nesterov Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/sys.c | 33 ++++++++++++++++++++------------- 1 file changed, 20 insertions(+), 13 deletions(-) diff --git a/kernel/sys.c b/kernel/sys.c index 5d0b44cd435..ddd28e261f3 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1022,23 +1022,30 @@ asmlinkage long sys_getpgrp(void) asmlinkage long sys_getsid(pid_t pid) { + struct task_struct *p; + struct pid *sid; + int retval; + + rcu_read_lock(); if (!pid) - return task_session_vnr(current); + sid = task_session(current); else { - int retval; - struct task_struct *p; - - rcu_read_lock(); - p = find_task_by_vpid(pid); retval = -ESRCH; - if (p) { - retval = security_task_getsid(p); - if (!retval) - retval = task_session_vnr(p); - } - rcu_read_unlock(); - return retval; + p = find_task_by_vpid(pid); + if (!p) + goto out; + sid = task_session(p); + if (!sid) + goto out; + + retval = security_task_getsid(p); + if (retval) + goto out; } + retval = pid_vnr(sid); +out: + rcu_read_unlock(); + return retval; } asmlinkage long sys_setsid(void) -- 2.20.1